Optimising energy usage so we can do everything with a 25 A mains connection and minimally upset the grid

When our home was built in 1972, people had fewer electrical devices. But more importantly, they heated and cooked with gas, which at that time was not only a cheap energy source but also one which few people in the Netherlands seemed to have realized could eventually run out, or cause earthquakes, or cause sea level to rise which could make much of our country uninhabitable, or that it could warm the planet and make many places uninhabitable.

Anyway, when our home was built the need for electricity wasn't so great and a 25 A connection was considered to be enough for average homes. That's what we have. 25 A * 220 V = 5500 VA (which is not exactly the same as 5500 W). We can therefore only draw a maximum of 5500 VA from the mains before we risk blowing the fuse. It also of course means that we can't send more than that much electricity back to the grid from our solar panels without risking blowing the fuse.

These days many people upgrade their fuse boxes, often switching to a three phase connection (often referred to as "krachtstroom") at the same time. Many newer homes are built with 35 A fuses on all three phases, allowing them to consume more than four times as much energy from the grid as we can take. This is the case even when those homes still use gas for heating. If everyone actually started using so much electricity at once, we'd be in trouble: it would require the grid itself to be upgraded and more power stations to be available to supply the demand.

We've not gone down the path of increasing the supply. Instead, we're trying to limit the energy usage of our home and keep our consumption within 25 A, even though we no longer have a gas connection so all our heating and cooking demands are now met with electricity. To do this we need to match our energy production with our solar panels so closely as we can, and to make sure that heavy users of electricity don't all switch on at the same time.

Balancing supply with demand
The wholesale price of electricity varies per hour depending on the consumption vs. production. The shape of the graph varies per month, with solar panels producing electricity in daytime in sunny months greatly reducing the value of electricity generated during those hours compared with the value at the same time in winter.

Graph of average wholesale prices of electricity per hour (source). Just trying to match this is a good start, but I ended up doing more as you can read below.

The price of electricity is directly related to the demand vs. supply. During the night most people are asleep and inactive thus energy demand is lower. During the day the peak demand is at breakfast time and dinner time, while peak solar production is in the middle of the day.

13 years ago when we first installed our solar panels, we would generally try to wait until the sun was shining before switching on large energy users like our washing machine, but nothing in our home automatically responded to the demand curve. At that time not many homes had solar panels so any electricity that we exported was always useful to someone. Our energy company gave us the same credit for every kWh that we produced as each kWh that we consumed, regardless of the time of day or the season. The situation is quite different now because 35% of homes now have solar panels and there are a great many solar farms in the countryside. That is why the price of electricity now drops so obviously during bright days. There are also many wind turbines now and on windy days the price also drops.

Automatically matching demand to supply
When I first installed our electric water heater it ran on a simple and inexpensive mechanical timer which switched it on at about 10:00 and switched off at 18:00 (it would actually stop much earlier when it reached the set temperature, unless we took a shower in the afternoon).

A now retired simple mechanical timer which used to switch our water heater on and off. I still recommend this as a good first step. It's easily affordable and very easy to use.

The timer was my first attempt at matching demand to supply, and if you can do nothing else I recommend it as it works quite well on average. The timer roughly matched the consumption of our water heater to when the electricity was flowing from our solar panels. However it didn't respond to other appliances using electricity at the same time (e.g. dishwasher, electric water heater in the kitchen, cooker, boiling a kettle) so we would quite often see our total consumption rise above what our solar panels were generating even on sunny days, while later on the same day we'd see the sun shining enthusiastically on our solar panels but the water heater would have stopped ages ago on reaching it set temperature, and we'd be exporting instead. A simple timer is much better doing nothing at all, but we can do better than that.

Reading from the meter
Dutch smart meters have a P1 port from which it's possible to obtain real time readings of the amount of electricity flowing in and out of your home. This provides electrically isolated serial data which it's safe and perfectly legal to use with a DIY project.

This is installed in our meterkast. An Arduino receives serial data from the P1 port, lights LEDs depending on energy usage (three green = 1500 VA export, orange = underfloor heating on) and passes the data to an ESP32 (the blue LED is the ESP32 activity light) which controls other devices in our home.

The first device that I attached to the P1 port was an Arduino programmed to display energy consumption on a set of LEDs so that we could see at a glance whether we were sending electricity to the grid (green LEDs) or consuming energy from it (red LEDs). It also included an alarm which would go off if we were approaching the 5.5 kW limit for consuming energy from the grid and automatically switched on underfloor electrical heating at any time that the temperature in the entrance hall was too low, or at any time that we were exporting a lot of electricity if the temperature was lower than we'd like it to be.

My intention at the beginning was to completely avoid wireless connections. The air filtration system uses a serial link between two Arduinos on the ground floor and the top floor (there was an existing conduit which made this easy). But for this project I realised quite quickly that it would require me to run a lot of cables. I was also going to need to know the time of day and the date. For those reasons I switched to using ESP32 controllers.

The ESP32C3
The ESP32C3 embedded boards that I'm using are very inexpensive, they contain a fast and powerful 32 bit processor, plenty of memory and even built in wifi. They're also smaller than my thumb.

An ESP32C3 controller board resting on my thumb.

The first, master, ESP32 is built into the same case as the Arduino, receiving the P1 data over serial from the Arduino. It couldn't replace the Arduino in that location because it doesn't have enough GPIO pins, but the two devices complement each other nicely. This first ESP32 works as a server and the other ESP32 powered device controllers connect to it to find out what they should do. I can see the status of all the devices on a simple web page at a static IP address hosted by the ESP32:

The single webpage hosted by the master ESP32 within the meterkast. It displays how much power we're importing, exporting, the current price, the rank (in the above this is the 4th cheapest daytime hour today), and also data about the hallway temperature and heating as well as data sent to it by various other connected devices. It's still quite cold outside which is why the temperature sensor by the front door went down to 12.7 C, and a few small heating elements were switched on in order to make sure no condensation can form. The "Tibber price" is the retail price including taxes etc.

 

The connected secondary devices all have a mains lead, two sockets (one switched with a relay) and use old phone chargers for their 5 V supply. Some of them use Dallas DS18B20 compatible temperature sensors. Some also have an override button which can be pressed to switch on the heater for a short period when it would otherwise not switch itself on.

The master ESP32 downloads the day ahead electricity prices at midnight and calculates a ranking of when the cheapest time is for any devices to operate (that's dayrank and nightrank on the status page above). Secondary devices can then  decide on which hours they can best consume electricity in order to reduce the price, and because these things are intrinsically related, best balance the demand on the grid.

For instance, we know that our main water heater heats its contents at a rate of about 7 C per hour. As a result, the controller can calculate ahead of switching on time how many hours it will need to raise the temperature from the currently measured temperature to the target temperature and it can optimise by only switching on for the daytime hours which rank below that value. At times of the year when our solar power can't cover all our demand it also automatically uses the cheapest nighttime hours using the same mechanism and the nightrank. This means in practice that in the morning when it has some value we allow our electricity to be exported to the grid, while around lunchtime when the price is at the lowest for the day the heater then uses the electricity rather than adding to the excess on the grid.

Note that these controllers also continuously monitor how much electricity is available either by importing from the grid or our exporting to it. Thus if we are producing just a little more electricity than the water heater needs and we put on the kettle to make a cup of tea, the water heater controller responds by switching off until the kettle is boiled, before switching itself back on. This means we humans get priority. The kettle, or anything else that we humans switch on and off, automatically gets whatever solar energy we are generating and we never have to manually switch off any of the automatically controlled devices so that we don't exceed the maximum available from our supply on a dull day. The water heater also automatically responds to such things as fluctuations due to clouds coming and going over our panels, and tries to optimise so that to the greatest extend possible we only consume electricity from our panels when we are generating it.

One of the heater controllers. A secondary ESP32 connects to the master and makes decisions about whether to switch on the heater plugged into the socket depending on the temperature measured by the probe, the time of day and the amount of electricity being imported or exported.

Whenever the energy price goes negative (which it did for three hours around lunchtime today), all the heaters are told they can go on and consume as much electricity as they want, pursuing a higher than usual target temperature. The extra solar panels on our garage are also switched off by another secondary ESP32 device when there are negative prices.

This is what is installed inside the controller for the solar panels on our garage. The stripboard includes two transistors used to safely switch the 5 V inputs to the double relay board from our 3.3 V microcontroller. There's also an input for power at the top and at the bottom a connection for the pulse output from an SDM120 energy meter in the garage. A 62 mm long piece of wire connected to one end of the antenna (red object marked C3) makes the ESP32C3 wifi more reliable.

Does it work ?
This system really does seem to do what I designed it to do. But as I've only just "finished" it (what hobby project is actually ever really "finished") I don't have any substantial data yet. When I do, it'll be added here as an update.

Screenshot from my energy supplier's app showing yesterday's electricity price and our consumption per hour (including taxes etc.). Nearly all the system worked yesterday. It should be better than this from now onward. The peak at just before 4 am is from the kitchen boiler, which comes on as a convenience for us during whichever is the cheapest hour at night in order to make sure we have some hot water in the kitchen in the morning. The peak at 12:00 is for an hour when we had negative electricity price, and the hours in the evening are still a bit of a problem even though most of our panels face South West, because when the sun goes down we don't have our own electricity.

Downloading ?
Once I know that this thing really works, and if people turn out to be interested, I'll make the code available to download somewhere. It's probably easier than starting from scratch. There's nothing amazing or patent-able about any of this - I'm not expecting to make money out of it. Mine is just a small contribution built on the shoulders of giants, including those who wrote the library code for TCP/IP, temperature sensors etc. I used to make a living out of writing code like that, but in the Arduino environment all the low level code for pretty much any device you want already exists. The work of others has made everything really easy to do.

Changing energy supplier
We've changed energy supplier from Pure Energy to Tibber. For the last few years Pure Energy have been paying us about €200 per year more for our exported energy than we paid them. I'm expecting a payment of about €280 shortly to cover the last year + one month that we were with them. Unfortunately, this happy situation wasn't going to continue: Pure's renewal agreement stated that they wanted to start to charge a fine ("terugleverbijdrage") of 14 cents per kWh exported to the grid, regardless of our trying to optimise our exports to be of the most use to them. This would total more than €400 per year. I tried to get a quote from them for a dynamic tariff (with prices per hour) and couldn't seem to get any sense at all from their salespeople.

I'm not expecting to be paid for dumping unusable electricity on the grid at midday in summer when it has no value. I've actually put quite a lot of work into trying to make sure that we don't do that, and to ensure that we use as much of our own electricity as we can, but I couldn't get any sense from Pure. Instead I've had to cancel their contract, which resulted in a snotty email in which they said they were sad to hear that we were no longer interested in using green electricity and gas ("We vinden het erg jammer dat je geen gebruik meer zal maken van onze groene stroom en/of gas!"). There's such a thing as "green gas" ? I don't think so.

Tibber, on the other hand seem to offer a straightforward easy to use dynamic tariff. I'm expecting that our total energy bill for the year will still be negative this year, especially given the recent optimisations detailed above. If you switch to Tibber and use the uitnodigingscode "dyd4ick5" then both you and I will receive €50 in credit for use in their online store - not that I've yet seen anything there which I think I would actually want.

Footnote 1: The ludicrous power of cheap embedded computers in 2025
I've often heard people say things like "this mobile phone has more power than the computers that took Apollo to the moon", but many people have no idea just how much more powerful those things are.

The little ESP32C3 microcontroller boards that I've been using have 160 MHz 32 bit RISC-V processors (including hardware floating point) which execute between 40 and 160 million instructions per second. They have 400 kB of RAM, 4 MB of flash, and include WiFi on chip as well as lots of other neat features. They consume less energy than I can reliably measure and they cost me $1.60 each.

The Apollo Guidance Computer was a truly amazing device given it's design in the mid 1960s. But while the performance was amazing then, it's not so amazing now: The AGC processor was clocked at just 1 MHz, used words 15 bits wide, executed "50000 to 100000 instructions per second" there was just 70 kB of (hand woven) ROM and 4 kB of RAM. They consumed 55 W and cost the equivalent of about $2 M each in 2025 dollars.

So the boards that I'm using execute instructions roughly 1000 times as fast as the AGC, they have about 100 times as much RAM and 60 times as much ROM (flash). And as my code doesn't achieve anything remotely as interesting as landing on the moon, these processors spend most of their time twiddling their thumbs in standby mode waiting for something to happen. By 1960s, 70s, 80s or even 90s standards this is a horrible waste of computing power.

Footnote 2: The ludicrous inefficiency of electric cars
I recently cycled past a garage and saw them advertising "175 kW charging". Yes, while we maintain our entire home on 5.5 kW, charging a single car can pull 175 kW from the grid. That's enough to blow the fuse of 30 homes like ours all at the same time !

Building a computer controlled ventilation system with HEPA filter to improve our indoor air quality

Introduction - why do we need this ?
In general, the Netherlands offers a reasonably good quality of life. Residential areas are well looked after, noise pollution is greatly reduced by quiet asphalt on roads, air pollution is fairly well controlled in most of the country (but not everywhere: certainly not for those living near the steelworks on the west coast). But there are three things which regularly cause ludicrous amounts of air pollution in this country: fireworks on New Year's Eve, Easter fires, and the idea that people have that it's especially "gezellig" to have a fireplace or stove burning wood in their living rooms. Luckily, none of our neighbours are especially keen on barbecues so the summer air quality is usually OK.

The government advises people not to burn wood for heating when we have weather conditions which will cause the pollution to accumulate, but it seems that almost no-one who burns wood for heating ever takes any notice of this advice. At the time of writing, the "stookwijzer" website advises people in our area that burning wood will cause nuisance to your neighbours and air pollution. From six o'clock this evening they advise that people don't use their wood burners at all because the smoke produced will cause health problems, especially for those with lung problems. But I expect that no-one will take any notice of this and our outside air will be thick with smoke this evening.

What I find especially absurd is that it's still September and we've not even had any cold days yet. Outdoor temperatures have not yet gone under 8 C. We've not yet used any form of heating at all and the lowest indoor temperature that we've seen so far was 19.5 C, in the middle of the night. Why buy firewood and spend weeks in the garden chopping it up (as some of our neighbours do), and then set fire to it when you could insulate your home instead and it'll be warm without any effort being required ?

Air filters
Initially we used air filters quite successfully to improve indoor air quality. They're also good to remove viral particles which visitors might bring with them. Though it's popular to pretend that Covid is "over", it's actually still killing about 200 people each week in the Netherlands, and it's similarly deadly elsewhere.

We have two Philips 800 series air filters. These adjust their speed and run quite quietly unless the air is full of particles, so you can sleep in a room with one active. Other companies produce good products as well, of course. The light on the top is purple because I opened our windows to let in fresh air and the neighbours were burning wood again.

A couple of years ago I also made this super inexpensive air filter. It looks like a cardboard box with a vacuum cleaner HEPA filter on one side and an old computer fan on the other because that's exactly what it is. It doesn't have the same throughput as the Philips filter, but it does clear smoke from the air in a small room surprisingly quickly. The 12 V fan is run from a 9 V "wall wart" power supply, so it runs slowly and reasonably quietly.

A house ventilation system
Free-standing air filters are good at removing smoke from the air, but they can't do much if you open a window for ventilation. Without ventilation, the CO2 level in a room rises rapidly due to nothing other than the occupants breathing. So we needed something else.

For the last couple of years I've been working on improving our indoor air quality. As we no no longer use gas the air inlet in the upstairs (2nd floor - two floors above ground) boiler room was not required for the heating system any more so I now use it to bring fresh air into our home. It opens into the boiler room, allowing air to mix and warm up if the sun is shining, but the air needs filtering before it comes into the rest of our home.

A fan which pulls air through a HEPA filter in the boiler room is controlled by a small computer. The fan is switched on if the downstairs controller indicates that the CO2 level is high. The computer also measures the temperature in the boiler room as well as on the upstairs landing so it can cool or heat the house (slightly) by bringing in cooler or warmer air when that's possible. It also monitors the temperature of the solar power inverter and switches on an external cooling fan when it gets warm. I already had to repair that inverter and I hope that this will extend its lifespan. The computer also can switch on a small heater in the boiler room if the temperature in the room is too low. This has not yet happened.

The wall outside the boiler room: An Arduino mounted on the wall next to the inlet for the incoming air. The green LEDs indicate when the fan is active (there are two speeds). The yellow LED indicates that the cooling fan for the inverter is active. The red LED indicates that the heater has been switched on. I'll cover it up so that it's less ugly some time soon...

Inside the boiler room. No-one usually comes in here, but I still need to cover up the circuitry of course. The HEPA filter is the same as the type used in the Philips air filter. The fan is an inline "quietline" fan from Hornbach, which seems to be one of the quietest inline fans available. The three relays are used to switch the two speeds of the fan and the small electric heater. I recovered them from the old gas boiler.

The other half of the system is downstairs. There's a controller on the wall in the living room where our central heating thermostat used to be. This measures the CO2 concentration and switches on the extractor fan in the kitchen as well as the incoming air fan upstairs (to attempt to create a balanced flow of air). Communication between the two devices works via a serial link using the same cable as linked the old thermostat to the gas boiler.

The downstairs controller measures CO2 concentration and will automatically switch on ventilation if the level is too high. Buttons allow selection of continuous low fan mode, 'visitor mode' which attempt sot keep an even lower CO2 concentration, and off mode which turns off the downstairs and upstairs fans. The latter is intended to be used if we find that the system is somehow overloaded and is bringing in smoke. The controller is also linked to the cooker extractor in the kitchen so that it knows to switch off the house ventilator fan when that is operating, and even if it was not otherwise required it will switch on the upstairs fan to attempt to approximately balance with the cooker extractor. The downstairs controller also has a light sensor so that it can automatically switch to nighttime mode when we go to bed.

We exhaust air from the kitchen on the ground floor, using the same duct as the extractor fan over our oven. Only one fan can operate at a time. Having air travel slowly from upstairs down to the kitchen helps keep cooking smells and condensation out of the rest of our home even after we've stopped cooking

Downstairs controller. This is also Arduino based, using a Nano this time to make the whole thing more compact. Sensors measure CO2 concentration, temperature and humidity. They agree quite well with my Aranet 4. The buttons on the front allow selection of constant low fan mode, visitor mode and no fan mode. The green LED indicates low fan setting, yellow indicates high and red indicates that the fan is currently off because we have a low enough CO2 concentration. The Aranet 4 made me realise that the concentration of CO2 in a house rises quite rapidly just through breathing. We saw the reading rise quite quickly to over 2000 ppm on winter evenings with the windows closed, but that no longer happens due to the ventilation system.

In the kitchen I put a a t-junction in the ducting from the cooker hood on the left of this picture so that an inline fan under the wooden cover on the right can also send air into the duct. It feeds from another duct on the right side of the photo which reaches nearly to the floor next to the refrigerator so that we take air out from a relatively low level in the room where it is cooler. Non return valves are used to prevent one fan blowing air back out the other. It's a bit ugly and I still need to cover the silver tube up. In this location I used a 125 mm version of the same inline fan as upstairs.

How well does it work ?
We now have fresh smelling air indoors even when the neighbours are doing their best to pollute. That was the intention and it's worked out well.

Though the design of the system as a whole takes advantage of latent heat in the boiler room, the upstairs landing and even of heat leaked out by our water heater, it makes no attempt at all to recover heat from the air which we extract from downstairs. This probably results in a slightly higher heating bill than we would have in a completely closed house, but the air quality difference is enormous. In any case, our heating bill is absolutely tiny so there isn't much to save. I may end up building a heat exchanger downstairs as that seems like a fun thing to try to do, but I doubt we'll be able to measure much of an effect.

We went through last winter with an incomplete prototype of the system. I initially had an old computer fan for the air inlet upstairs, but it wasn't adequate to keep up with the downstairs fan. It also initially just switched on and off with a timer and there was no attempt to even try to balance flow with the downstairs fan. A roughly balanced flow of air does seem to create a better result overall.

Something that surprised me is how poorly CO2 travels between rooms. With no open windows but the door between our bedroom and the hallway open, the CO2 level can reach over 1300 ppm in our bedroom despite the hallway being around 700 ppm. I was surprised that diffusion didn't do a better job of lowering the CO2 concentration in our bedroom. Running one of the Philips air filters in the room moves air around enough to lower the concentration by about 200 ppm. But to achieve a really low CO2 concentration around our heads I think we would need a fan blowing air through the doorway.

Of course in the past no-one had a CO2 meter so we could never measure these things. When we first had the Aranet 4 but we didn't have any kind of ventilation system we'd see the CO2 ppm race up and beyond 2000 ppm in the evening in our living room just from our breath. It also headed in the same direction in the bedroom overnight. I suspect that we've unknowingly slept with very high levels of CO2 in past years without realising it and I think the same is true for most people. CO2 rises very quickly in any room with closed windows and doors, and using candles also rapidly increases the CO2 concentration.

I think a ventilation system has much to recommend it. It's a step beyond what can be achieved by air filters on their own. This system works. If there's interest I'll put the Arduino code somewhere that it can be downloaded.

Update January 29 2025
I just replaced the air filter:

Old air filter on the left, new air filter on the right. The old one actually looks worse than this in real life. It was actually slightly used in an air filter in our home before I installed it in the ventilation system in September, but it certainly didn't look like this.

The new air filter is completely white in colour and a little translucent, while the old one which has been installed for about four months is very dark and completely opaque. All that black dust would have been floating around in our home for us to breath in had I not installed the air filtering system. The majority of the dust almost certainly comes from wood burners which some of the neighbours use to heat their homes, but fireworks at new year and road traffic will also add to it.

Another notable change is a reduction in condensation, for instance around the inefficient thin double glazing fitted in our back door. This is because we have lower humidity in our home now because the moist air that we breath out is extracted by the ventilation system.

Saving energy with new appliances ?

I've always been a bit skeptical about the idea of replacing appliances early in order to save energy. The embedded emissions in creating large appliances are not small, so you'd have to make a pretty big saving in ongoing emissions for it to be worth scrapping a device early to install another in its place. Generally speaking, I prefer to repair things and keep everything working for as long as I possibly can. But sometimes it does make sense to buy something new.

Since we moved into our home in the Netherlands 17 years ago we've done a lot to make our home more energy efficient. We've improved the insulation, replaced the windows, built a ventilation system (which I'll write about in due course), removed the gas supply altogether, and installed solar panels to generate more electricity than we consume. But the inside of our home hasn't seen so much work.

The kitchen was a bit tired looking when we moved in, and it's not got any better with almost two decades of use, so this year I've been working on improving things.

The kitchen cabinets were mostly actually still OK but the doors mounted on them, which were made of thin white plastic coated chipboard, were falling apart and they looked super ugly. Rather than throw everything away I've made new doors from scratch to fit onto the old cabinets, and also constructed new cabinets of plywood where they were needed. This is also much cheaper than a complete new kitchen, so it's a better fit with our limited finances. We then had the question of the refrigerator. The old built-in refrigerator was in the house when we moved in and I always had the idea that it consumed at lot of electricity because it hummed almost constantly. Unfortunately, until I started taking the kitchen apart I couldn't reach the socket where it was plugged in and measure it.

Measuring refrigerator/freezer consumption
The old (late 1990s / early 2000s) refrigerator turned out to use a whopping 500 kWh of electricity per year. That's five times as high as some newer models of the same size, small refrigerators without freezer compartments. We also had a freezer which we'd brought with us from the UK. This was a Liebherr unit which was a well rated model when we bought it. I'd looked around and found one of the first devices available which did not use CFC style refrigerants. But I measured the freezer as consuming 250 kWh per year, which is actually not more than some new comparable models. But 750 kWh per year in total for refrigeration is ridiculous.

New A-rated fridge/freezers with a similar capacity to our old fridge and freezer combined are rated as consuming about 110 kWh per year. None of the A rated devices are built in types so we had to choose between free-standing fridge freezers. We chose an Inventum KV2010B as this company gives a standard 5 year guarantee and provides reasonably economically priced parts for repairs.

New and slightly imposing fridge/freezer in our kitchen, next to kitchen units with newly constructed home made doors. For some reason all the A-rated fridge freezers are black. Whatever happened to "white goods" ?

The real world consumption of the KV2010B in our first week works out as equivalent to 190 kWh per year. That's above the rated 113 kWh / year according to the manufacturer. However the standardized tests are carried out, the conditions are clearly not the same as ours over the last week. Of course a week at the end of June is warmer than the annual average and I expect this appliance will use a bit less electricity in colder months (our old devices also consumed less in winter than in summer).

Energy rating certificate for our new fridge/freezer.

The same refrigerant, R600a, or isobutane, is used in the new fridge freezer as in our old freezer. I don't know what was used in the old refrigerator which we didn't choose, but it was probably something horrible. When we bought the freezer this was an unusual refrigerant but it seems to be commonplace now. That's quite an improvement. R600a has a very low GWP (global warming potential) of 4 compared with CFC refrigerants which can be in the thousands. It's not quite so low as the R290 of our heatpump, though.

The value of the electricity saved
We expect to save almost 600 kWh per year with this new appliance in place of the two old devices. That's significant. It's almost as much electricity as we used for all our heating last winter. It's also about the same as the output from two of our solar panels. I think it's worth noting that much of the saving will occur during night-time, on the shorter days of winter, or when there's not much sun. i.e. at times when it's especially valuable for us to save electricity because we don't have so much of it available from our own panels.

In the Netherlands the total retail cost of electricity including all taxes is currently around 25 c / kWh so a saving of 600 kWh of electricity is worth about €150 annually. Having paid €799 for the appliance the appliance should pay for itself in about five years. It will also save 134 kg of CO2 each year (at 223 g / kWh average emissions for NL). The actual cost for us is much more difficult to work out because we generate more solar electricity than we use.

Disposing of the old devices

The people who delivered the new fridge/freezer took the old fridge away for recycling, but they would only take one appliance, so I had to take the freezer on a 7 km trip to the local recycling centre by bike. Both of the old appliances were the same size as this.

At the recycling centre they picked it this way, putting considerable pressure on the radiator at the back and risking causing a leak of the refrigerant. That's why I didn't buy a CFC containing freezer in the first place. I suspect that even when they're supposed to be safely removed, only a small percentage actually are safely removed.

An earlier trip to the recycling centre. Judy and I transporting parts of the kitchen cabinets, mostly rather nasty damaged doors but also the parts which contained the old built-in fridge.

Update: Energy meter problem
It turns out that our plug-in energy meter has a problem. It's reporting 270 V as the voltage of our mains supply instead of the ~225 V which the multimeter reports. 270 V is above the legal maximum supply voltage. I believe the multimeter. Anyway, this 20% high voltage reading probably translates into a 20% over reading when measuring Watts as well, so the first week of the new refrigerator was probably a lot closer to the manufacturer's specification than what I measured.

Further update: Brennenstuhl PM231 review: it completely failed
In January 2025 I noticed that this energy meter had now completely failed. It usually now doesn't boot up at all, just displaying all segments on as shown in the photo below even when the reset button is pressed, but occasionally when it does get as far as booting it now claims that voltage, current, power and power factor are all "zero". I contacted the manufacturer and they're not interested in doing anything about it. Drilling out the weird three sided security screws allowed me to take a look inside, but there's no obvious failed part so I don't think I'll be able to repair it. The case might be usable for a DIY project with a relay inside.

Don't buy a Brennenstuhl PM231 energy meter. They don't work for long before they start to fail in a way in which they give inaccurate results. The company isn't interested in fixing them.

Brennenstuhl PM231 energy meter. Don't buy one of these. They slowly become less accurate over time and then completely fail. Brennenstuhl won't repair them because the fail occurs outside of the short guarantee period, and is probably unnoticed by most people initially. After all, these gadgets spend most of their time in desk drawers, not constantly in use.

Twelve years of rooftop solar power

Our rooftop solar power system was installed 12 years ago today. In total they've generated 40900 kWh since installation. While last year (2022-2023) was a record year for output from these panels, this year (2023-2024) was not. The end of 2023 and beginning of 2024 were marked by particularly grey and dull weather so this  output is not surprising. But the output of 3362 kWh over the whole year is still only slightly below the 12 year average of 3378 kWh per year.

Total output of our solar power installation per year. The blue columns are the contribution of the 12 year old rooftop system. The red shows the additional power generated by the extra panels we've installed on our garage roof.

The garage roof panels added an additional 1416 kWh to the total for the year. These were installed as we wanted to to compensate for the consumption of the heat pump and electric water heater that we installed when we got rid of our gas connection.

This winter was the dullest that we've recorded, resulting in the blue bar for March 2024 being easily the lowest in the graph. Even the substantial contribution of the new panels, shown in red, didn't result in higher total output than we have seen in brighter March months in past years from the rooftop panels alone. But the extra panels still helped us to generate a higher proportion of our consumption this winter than we have done without them.

Our rooftop panels having been operating for 12 years also of course means that the inverter has been operating for 12 years. The inverter actually only lasted for six years and three months before it failed due to poor soldering and the manufacturer refused to fix it. I fixed it myself and the repair that I made has very nearly doubled the life of the inverter thus far. I am still very irritated that ABB, the inverter's manufacturer, preferred to tell us that the whole inverter had reached the end of its life and needed to be thrown away and replaced with a new one when they could have made the same simple repair in order to keep it operating.

Anyway, the system as a whole is still working very well. It's difficult to work out exactly by which date this system paid for itself because the electricity price has changed over time. But the cost of electricity to consumers, including all taxes etc., has always been higher than 19.5 c, so I think we can now reliably state that the original purchase price of €8000 has been repaid by the solar panels and inverter together. Since 2012 the cost of solar panels has dropped precipitously and I expect the extra panels on our garage will cover their cost in under 4 years.

If you've read this far you'll probably also be interested in my blog post from four days ago about how the heat pump, electric water heater and solar panels together have reduced our energy bill to less than zero.

Relative cost of heating with a heat pump vs. gas (How to reduce your heating bill by 100%)

We've now had our heat pump for one whole winter. For the purposes of this blog post, "winter" refers to each period of November through to and including March, as those are the months when we use heating. Because we've gone through our first winter period with the heat pump we can now make a comparison with other winters when we used gas for heating and work out both the financial cost and (more importantly) the emissions due to both heating options.

This house was cold
We've lived in our home since 2007 and I've recorded our energy consumption consistently each month. Our home was built in 1972, just after the discovery of gas under the Netherlands. At this time it was assumed that gas would always be an inexpensive fuel source and no-one was making much effort to make housing efficient. We had very little insulation and single glazing in most of the windows. Only the living room, dining room and kitchen had old and basic double glazing.

When we worked out how much the first winter's energy bills were going to be this really shocked us and we ended up setting the thermostat as low as 14 C and in order to reduce the gas consumption we even turned the heating completely off on some of the coldest days of winter until our children were about to come home from school. This was quite unpleasant so we started some steps to insulate our home even in the first winter in order to reduce the energy requirement.

Each insulation job contributed to reduced heating requirements and a warmer house. At first there isn't much of a reduction in consumption to see, but that's because we were compensating by living with a bit more warmth each winter. The difference between the blue and red line was the consumption of the pilot light in an old gas water heater that we replaced with an electric water heater last year.

By the winter of 2022/2023, the last in which we still had a gas connection, our heating consumed just 287 m3 of gas rather than the average of just over 1110 m3 of gas per winter that we had burnt over the first four years that we lived here. That's about a 70% reduction in energy input, without changing the heating system.

This winter we used an air-air heat pump in our living room as almost the only heat source between November and March. There's a heated towel rail / IR panel in the bathroom which comes on with a timer every morning but otherwise no permanent heating upstairs to replace the no longer used radiators. We did make very occasional use of portable electric heaters. We've been quite warm. It's certainly far more comfortable upstairs now without any heating than it was in the first years that we lived here when hot radiators struggled to keep uninsulated bedrooms with large single glazed windows up to a comfortable temperature.

Energy consumed
Our heat pump consumed 682 kWh of electricity over the five month winter period. That's roughly equivalent to the energy content of 68 m3 of gas. i.e. this winter we used only about 6% as much energy to heat our home as was the case when we first moved here.

I have to admit that this was not a particularly cold winter, but it was especially grey and wet so the solar panels that were supposed to run the heating didn't do as well as was expected. Despite that, even this winter, they still generated more than 30% of the electricity that we consumed over those five months so we had to buy just 470 kWh of electricity from the grid to run our heating.

CO2 output
We're signed up to a green tariff which promises us 100% green electricity ("100% groene stroom uit Nederland") but I never know if you can really trust such a claim so I will instead take the an average carbon intensity of 223 g per kWh for Dutch electricity in 2023 as a worst case scenario for our CO2 output.

That worst case scenario suggests that our heating may have produced 105 kg of CO2 this winter (470 * 0.223), which is a huge reduction compared with the emissions of our gas boiler when we first moved in. Our gas heating CO2 output averaged around 2000 kg of CO2 per winter over the first four years that we lived here. i.e. the worst case scenario gives us a 95% reduction in CO2 output for heating due to a combination of insulation and electric heat pump replacing the gas boiler. The first 75% or so of that reduction in emissions is due to the insulation and the heat pump is responsible for the rest.

What would it have cost if we were still using gas ? What has it cost this year all-electric ?
We could never afford that level of gas usage so we shivered more than most when we first came to live in the Netherlands. If we'd continued burning gas at the rate that we did in the first four years that we lived here then it would have cost over €1600 for heating this winter. Instead of this, we insulated our home in order to consume far less heat. If we had stayed as we were last winter, with the same insulation but with gas heating instead of the heat pump, then we'd have consumed about €400 worth of gas over the winter period. That's already quite a saving over the average.

According to our energy supplier, the gas consumption of an average home like ours (semi-detached / 2 onder 1 kap) over the winter period is around 1360 m3, which is actually higher than what we found unacceptable when we moved here.  At the current price of gas quoted by the energy that gas costs an average family in an average house like ours about €1930 each winter and each of those homes will produce over 2400 kg of CO2 for heating over that period.

But our gas supply was removed last year and we're all electric now, so what did it actually cost us to heat with the heat pump ?

For the last year we've been paying our energy company €5 per month for the electricity connection only (there is no gas connection). We've just come to the end of the yearly billing period and they now owe us more than €200 for the excess electricity that we produced from our solar panels and contributed to the grid. i.e. our energy bill is negative.

End of year summary from our energy company. They owe us €252, and we can continue to pay them €5 per month next year.

Insulate ! It makes a huge difference to your comfort and your bills. Then you can install a small and inexpensive heatpump.
Every step that we've taken in the past to better insulate our home has led to lower bills, lower CO2 output, and more comfort. It took us a while to do everything because our income is small so we couldn't do it all at once. But do everything you can, as soon as you can. It's really worthwhile to do all of this before you even think of replacing the heating system.

If you're in a rented home that makes things more complicated, but encourage your landlord to everything they can. This is a no-brainer for any sensible landlord as any work done adds to the value of their asset. If you're in an apartment and shared ownership of walls and roofs is a problem, then do whatever you can to get the organisation (probably a VVE in the Netherlands) to make changes. That's a difficult situation because you have to get a lot of people to agree. But it's all worthwhile. Every penny spent on heating is wasted, every penny helps to pollute the planet, so let's stop spending so much on it.

Reducing energy input
Something that seems quite crazy to me is that people replace absurdly oversized gas-powered boilers (ours was rated at 28 kW!) with equally absurdly oversized heat pumps. Yes, they'll cost less to run and have lower emissions than gas heaters, but they still consume a lot of electricity. Those high powered heat pumps require a three phase connection (single phase is limited to 16 A / 3.5 kW in the Netherlands) in order to suck in enough current to produce their huge outputs. What we installed has a 3.5 kW maximum output and it consumes a maximum of about 1 kW when it's in use. It it really warms the room up quickly when it starts up, but it soon settles down to a lower power mode to maintain temperature.

I think it's important that we try not only to switch away from fossil fuels but also to reduce our total energy consumption. The energy transition certainly won't be made easier if we try to achieve that transition by installing lots of electrical devices which consume enormous amounts of energy.

Once a house is well insulated it just doesn't need much heat input. At that point, an inexpensive air-air heat-pump like ours can keep your home at a comfortable temperature. Our heat pump and everything I needed to install it myself together cost significantly less than one year's average winter heating bill. The result of installing this device is that we no longer have a heating bill. Why would anyone not try to do this if they can ? We may now install a second one upstairs in the room where I work, but that's really a luxury: I've been fine this winter. If I didn't work from home I'd probably not be considering it at all.

Effect of heat pump and electric water heating on our electricity bill in December 2023

Since we had our gas supply removed last year we've used electricity for both our water heating and our home heating. Unsurprisingly, this means we're using more electricity, especially in winter months as we no longer burn gas for heating.

We consumed 222 kWh more electricity from the grid in December 2023 than we did in December 2022.

Our heat pump consumed 168 kWh of electricity in December and the water heater used about 70 kWh. It's been a bit chilly upstairs sometimes so we've also used some small electric heaters occasionally, but clearly we also managed to reduce our consumption of electricity elsewhere as otherwise the numbers don't quite add up.

We had hoped to compensate at least some of the increased electrical consumption by expanding our solar power system. Unfortunately, due to the last quarter of 2023 being incredibly grey and rainy (a new record for rainfall was set, largely due to rainfall in the last three months of the year), the expanded system produced just 42 kWh in December, vs 60 kWh from the smaller system a year before.

Part way into January, waiting for ice to melt off the extra panels so that they could have full performance, if only the sun came out properly...

The gas we didn't burn, and the resulting CO2 emissions
In December 2022 we burnt 125 m3 of gas. That's less than an average apartment and well under half the average for a house like ours. This year we of course burnt no gas at all. 125 m3 of gas contains the equivalent of about 1250 kWh of energy, so the 222 kWh extra electrical energy that we drew from the grid was considerably less than that contained in the gas that we used to burn.

The 125 m3 of gas which we burnt in December 2022 produced 223 kg of CO2 (factor of 1.78). The average CO2 intensity of Dutch electricity for 2022 was 321 g / kWh meaning that our extra 222 kWh of electricity consumption in December 2023 will have led to 71 kg of CO2 emissions if our electricity was of average CO2 intensity for the Netherlands. That's a worst case scenario as even in the exceptionally grey month which just passed, 8% of our electricity still came from our solar panels. We are of course also signed up to a tariff which claims to supply us with zero CO2 green electricity (despite this not always being possible to do).

Therefore in the worst case our emissions in December as a result of replacing the gas supply with electricity were less than a third of what they would have been if we'd continued to burn gas. In the best case we did a lot better than that, but we're then in the realm of guesswork based on where our electricity might really have come from. When a large proportion of Dutch electricity still comes from burning fossil fuels it's nonsense to ever claim that electricity has zero emissions.

An average Dutch household in a home like ours will have consumed around 300 m3 of gas in December, resulting in around 530 kg of CO2 being emitted so in the worst case we had around 1/7th of the emissions of an average household.

Update: Dutch emissions per kWh electricity may actually be much lower.
It's possible that emissions in 2023 per kWh were actually much lower than 321 g. A smart guy on Mastodon calculated that the true figure was actually around 223 g / kWh for the Netherlands in 2023. This would have the effect of reducing our worst case emissions for heating in December to just 50 kg, meaning that we emitted about a fifth so much CO2 this year compared to last, or around a tenth of the amount emitted by an average similar size household using gas for heating.

Costs
It's difficult to work out exactly what the cost of gas would have been, but based on pretending to take a new contract out with our electricity supplier it appears that they would have charged us about €200 for the 125 m3 of gas had we used it in December. The cost of the extra electricity that we used is about €100.

But actually we deliver more electricity to the grid each year than we consume, so we only pay €5 a month for energy. At the moment our supplier says they still owe us about €260. This amount becomes due in mid February so we won't get quite that much returned to us because we expect to use more electricity than we produce for heating in January and February as well.

How well did the heat pump work in the cold ?
The lowest temperature in the morning that we've seen so far was about -7 C. There was plenty of heat from the heat pump. It does need to pause and defrost itself occasionally when it's cold outside.

Onward and hopefully downward
December is the worst month of the year due to the short daylight hours. Let's hope we can take proper advantage of the sun in January, February and March as more sun means lower emissions.

This may look like a grey rectangle but it's an actual photo of the sky today. The sun is roughly in the centre (that's a guess as I couldn't see it). Not exactly ideal weather for solar power.

An all-electric home with air conditioner (aka air-air heat pump) as heating

Regular readers will know that we had the gas supply removed from our home in April this year. This left us with no central heating in our home. We used a portable 400 W electric infra-red heater in he living room on some of the cooler days of March and April, which worked well enough for those months because our home is now very well insulated, but we knew that in the middle of winter we'd need a more effective form of heating. Having the gas supply taken out meant that we were working under a time constraint - we had to find a solution before next winter. We now have that solution.

Electrical heating
Electrical heating is 100% efficient. All the energy which goes into an electric heater will be turned into heat. Actually, the same thing applies to all other electrical appliances - some of the energy may turn into mechanical movement, calculations, light, sound etc. but it all becomes heat in the end. So everything electrical helps to heat your home at almost exactly 100% efficiency (we lose a tiny bit from light shining out of windows and other small effects).

But just because resistive electric heating is 100% efficient that doesn't mean it's actually a particularly good way of heating your home. Electricity costs more per kWh than gas. Also if gas is being burnt to generate electricity then due to inefficiencies of the power station and transmission lines more gas will be burnt in total to heat your home than would be the case if you had an efficient modern gas central heating boiler.

For a while, around 50 years ago when the future looked like it might be nuclear powered, the idea of storage heaters was popular as they would allow excess "too cheap to meter" electricity generated at night by non-throttle-able nuclear power stations to be used as heat during the day. Homes in the UK were built as "all electric" and I lived in some homes with that type of heating. It worked reasonably well. There was a logic to it, but nuclear is not a technology which is going to come along and quickly save us from ourselves right now. Many of those homes were later retrofitted with gas, which now looks rather unfortunate. Our home in the Netherlands has gone in the opposite direction. Built originally against a promise of cheap endless gas, we've transformed our home to be fully electric.

Heat pumps
Heat pumps on the other hand are popular now. They appear to do something magical in that they generate more heat energy in their output than they consume as electrical energy from their supply. There is of course no magic involved at all. In this house we obey the laws of thermodynamics and we're not creating something out of nothing. Heat pumps actually (mostly) just move heat around. When heating a home in the winter they take heat out of the already cold air, water or ground outdoors, making it even colder, so that that heat can be emitted indoors. It's a neat trick.

The problem with heat pumps sold to replace central heating boilers, providing hot water to flow through radiators or under-floor heating, is that they're very expensive and they're over-sized for many well insulated homes. When I calculated how much gas we burnt last year to heat our home it became obvious that the 28kW gas central heating boiler installed in our home had only burnt enough gas to have operated at full power for the equivalent of about three days in the whole year. The lowest output heat pumps are rated at around 7 kW so one of those would have to run for about 10 days in the year. It would still lose a little in efficiency because the boiler would be on the top floor and the hot water would still have to be piped two floors down to reach the living room, losing some of the heat along the way (even with well insulated pipes), but total energy consumption would be 400 kWh over the year. By comparison, direct electrical heating to provide the same amount of heat would consume about 2000 kWh of electricity in total.

Air conditioners
Air conditioners work in exactly the same way as a heat pump. Many models of air-conditioner can also operate as heaters and when so used they have the same high efficiency as heat pumps. i.e. they produce far more heat as output than they consume from the electricity supply. Even though they don't attract a subsidy they have a much lower price than a heat pump, so we decided to install an airconditioner as our source of heating in the winter.

We could have installed two air conditioners, one up and one down, but we're instead going to try to live with just one in our living room together with occasional use of a portable electrical heater upstairs should it prove to be necessary. We have rarely turned on the upstairs radiators in our home in the past so we clearly don't have much need for heating upstairs, but if it turns out to be necessary nothing excludes the installation of a second air conditioner upstairs. Two air conditioners still cost only about half the price of a heat pump.

The nasty environmental problem with air conditioning and heat pumps
One of the things that has put me off both heat pumps and air-conditioners in the past is the high environmental impact of florinated refrigerant gases. These not only have a disastrous effect on the ozone layer but that also can have a greenhouse effect greater than 10000x that of an equivalent amount of carbon dioxide (GWP = global warming potential). Even the R32 refrigerant often touted as environmentally friendly has about 670x the global warming potential of the same amount of CO2. 

While it's supposed to be the case these days that refrigerant is recovered when airconditioning systems are taken out of use, does that actually happen in reality ? Photos showing destroyed airconditioning units dangling from buildings in war-zones and after natural disasters indicate that a considerable number of these units don't get decommissioned in a manner which is sympathetic to the environment, and even if they are, what do we do to ensure that those gases never escape once they are extracted from an old airconditioner? I'm not convinced that these gases can be contained for the rest of time and do all the old gases make their way safely to one of the few plants which can destroy them ? I don't think I'd like the answers to these questions. Luckily, there is an alternative:

The solution: R290
R290 is a refrigerant with a GWP of just three. Not three hundred or three thousand, just three. On release it has a greenhouse effect only three times as bad as CO2 and it has no no effect on the ozone layer. There is very little refrigerant in an airconditioner, less than half a kg. As such, the total harm than can be done by releasing this gas is very small. R290 is actually just propane, so not a florinated gas at all. As a result of this it's also legal for people to work on R290 systems themselves. No "f-gas certificate" is required for working with R290 here in the Netherlands because it is not an "f-gas". DIY is good - it should reduce the total cost and I like doing stuff.

Our choice of airconditioner
R290 split airconditioners have been promised for some years but they still seem to be new on the market. I picked the only model that I could find on the Dutch market earlier this year, a Midea 3.5 kW air-conditioner. This was the first model of airconditioner ever to win German Blue Angel environmental certification. It took a while to find a supplier as seemingly not many people sell them, but I did find a supplier in the Netherlands.

As this airconditioner has an SCOP of 5.2 it will in principle consume only about 400 kWh of electricity a year to provide as much heat directly in our living room as our old central heating boiler put into hot water which it then pumped around the house. It should operate efficiently down to -15 C which is almost as cold as it's ever been here. It's never been that cold for the entire day. But anyway, if it gets really cold I guess we'll have to go out cycling for a bit to warm up.

To provide power we already expanded our solar power installation with two extra solar panels which will produce about 700 kWh of electricity a year. In total we should easily generate enough electricity each year to supply the air conditioner as well as the electric water heater (for which we installed another two solar panels) and every other electrical device in our home. While in winter months even our over-sized solar setup won't generate enough to run everything, the overcapacity should mean we are able to operate at least mostly on our own electricity for most months of the year.

Now some DIY
The airconditioner turned up a couple of days after ordering and then I ordered a few extra parts to complete the installation.

The outdoor unit in a box. Clearly labelled R290 / Blue Angel. Quite heavy to move.

I needed refrigerant lines and electrical cable and I chose rubber feet for mounting the outdoor unit on the ground outside our home. We could have mounted it on the wall but I thought that brought a higher possibility of vibrations being carried into our home (the unit doesn't vibrate much and I now doubt this would have been an issue). Also the wall mounting brackets available didn't seem to be large enough to allow enough space. The outer unit is recommended to be installed 30 cm from a back wall for maximum efficiency.

The first thing was to determine the best place for the inner unit. I decided to place it half way along our living room wall and so high as possible. The instructions suggest a minimum of 15 cm between the unit and the ceiling and that's about the height at which it's mounted. I didn't want visible ducting inside our home so I drilled a single large hole through which all the pipes and wires had to run. This had to run downhill to the outside in order to make sure that the condensate would find its way out through the wall, and in my case I had to run it at a more extreme angle than I otherwise would have because the carport outside our home is attached to the outside wall at the same height as the inner unit of the air conditioner is on the inside wall.

Drill with 70 mm attachment for drilling through concrete. This does not go through in one push. You have to work at it a bit, and stop to let it cool down quite often. You also have to pull out chunks of concrete and brick which fill the tool and stop it from working. It took more than an hour to drill the hole. I had to work from both sides as the wall is over 30 cm thick so I first drilled all the way through both layers of the wall with a long 12 mm drill bit.

Hole in the wall, sloped downward to avoid the carport outside. I lined the hole with PVC pipe, cut lengthwise so that it could adjust to the right shape and sealed with PU foam. Note: a lot of concrete and brick turned into dust. I worked with a mask on as well as ear defenders and had a vacuum cleaner running continuously, which helped to avoid too much dust finding its way elsewhere in our home.

The refrigerant tubing comes as a reel of copper pipe with insulation already fitted. I was cautious of bending this copper tubing as I'd expect it to flatten if bent too sharply but it unwound without causing any harm to itself and could be poked through the wall to the other side also without harm. I could then attach the pipes on the outside to the external unit. In my case exactly three metres of pipe was required. This was supplied with the required flare to fit both units, making the job a bit easier.

Black plastic covers on the piping of the indoor unit. The indoor unit has high pressure nitrogen inside so there is a hissing noise when they are loosened. That does not mean that refrigerant is leaking - the refrigerant is in the outdoor unit. However it's important that there should be a hissing noise as that indicates that the indoor unit has held pressure, also that it's not been contaminated with damp air. This didn't seem to be written down anywhere so I thought I'd add it here.

By this stage I'd put everything together so that in theory it was ready to go, I then tried to find a contractor to carry out the final step: Before you can set an airconditioner into operation it's necessary to draw a vacuum in the pipes so that there is no air in the system. Only after that has been done is it possible to release the refrigerant from the outdoor unit into the system. Some people don't bother with this step and I assume that their airconditioners don't operate to their full potential as a result.

I didn't have a vacuum pump and I thought it reasonable to let someone with experience do this part of the job for me. I even thought it might save a bit of time. However that turned out not to be the case at all. This was the most time consuming part of the whole project ! I waited over a month for more than ten different contractors to get back to me. They either said they would only with a certain manufacturer's airconditioner, or they wouldn't check other people's work, or they said they were too busy. Eventually, one guy said he'd come and do it. He made an appointment for two weeks in the future... and then he didn't turn up. So this was also to be a DIY job.

The standard price for setting an airconditioner in action is €200. That's what everyone who said they could do the job said they'd charge me, though none of them seemed to need the money. In the end I bought a vacuum pump for €115 expecting to need adaptors and pump oil in addition, but it turned out that everything I needed was in the box with the vacuum pump. This was a very simple and quick job to do, apart from the waiting around. No more than half an hour of actual work.

Vacuum pump pulling the air out of the tubing. After half an hour I turned off the blue tap and disconnected the yellow hose.

, which was never an option

The next morning we still have "-1 bar" relative to ambient air pressure so it didn't leak (i.e. close to 0 bar in reality negative pressures can't exist)

So the pump was set up and drew a vacuum for half an hour. I then I disconnected the pump, leaving the pressure gauge displaying -1 bar overnight. After that I let some of the gas into the system, the pressure rising to about two bar so that I could check my connections to the pipework with soapy water to see if there were any leaks (which I'd have to tighten up before going further). There were no bubbles forming so I let the rest of the gas into the system, still no bubbles, then I removed the meter from the outdoor unit, fitted all the covers and switched on. The airconditioner works.

Outdoor unit. The white cover over the cables and tubes goes to just slightly underneath the carport. The inner unit is on the other side of the wall a few cm higher. The switch on the wall is a legal necessity. The watering can catches the condensate so that we can use it in the garden. If the air conditioner is set on cool mode for an hour it produces a surprising amount of water.

The inner unit on the wall in operation. No visible wires or tubes. Everything works. We've used it to cool a couple of times and it's very effective. Heating has been tried only momentarily because it's summer and we really do not need heating yet. Hopefully this will work as effectively as we need it to in winter. It's very quiet in operation. Almost nothing to hear at all, certainly much less noisy than a table fan even on a low setting. The displayed temperature is what we were cooling to in the summer, not what we heat to in the winter.

We have a heating solution!
So we now have a heating solution for next winter. It will consume less electricity than a heat pump but hopefully provide us with enough heat. It's a bit of an experiment for us to say that we're only going to heat the ground floor, so wish us luck. The kitchen is a bit of a worry because it's around the corner from the living room and dining room. But the kitchen also has other heaters in it, such as a small water heater under the sink, the refrigerator etc. The extra insulation job that I did on the kitchen door a few days ago was specifically intended to try to keep the kitchen warm when we are heating just the living room. We have other plans and there are more things that can still be done. Watch this space.

Did I forget to mention summer ? We installed this air conditioner primarily to provide heat in the winter, but obviously an air conditioner can also be used as an air conditioner. We have done that for a couple of afternoons when it was very hot and I have to say that it's very pleasant to have a cooler home when it's hot outdoors. Luckily these times also coincide with our having excess solar power and the grid being quite full due to the amount of sun beating down on everyone's homes, so we find ourselves still exporting electricity while the airco runs. I don't see a downside to using the air conditioner in this way sometimes. With weather becoming more extreme we might well use it more often. But we don't intend to live in a permanently air conditioned home. When the weather allows, it's much nicer to open the windows.

Getting rid of the radiators and central heating boiler
A job that I've not yet done is to get rid of the radiators and central heating boiler from our home. There's a lot of metal involved, a lot of heavy work. They take up a surprising amount of space. We didn't get rid of these things when we first had the gas removed because that would mean burning a lot of bridges. We might have decided to install a heat pump instead of air conditioning, and that could have worked with our existing radiators (which are oversized to suit our originally under-insulated home). While I'm quite confident, this also means that if the air conditioner doesn't work out this winter, we could still make use of the radiators next year with a heat pump. There's no need for us to rush this.

Car airconditioners
What's the deal with car air conditioners ? From what I can tell these leak all the time and drivers respond by having them "topped up" with more refrigerant, sometimes annually. If there's a crash (and there are always crashes) then the refrigerant is released and having its awful effects on our climate and the ozone layer. Air conditioning in cars really should not be allowed, certainly not with use of refrigerants which are more destructive to the environment than R290.

Cars make everything worse.

Update: The first cold month - November 2023
November this year was colder than usual. We had snow and persistent freezing temperatures which we've not had in November for many years. There was also very little sun. So how well did the heat pump work ?

Gas usage November 2022. We consumed 52 m3 of gas, compared with 119 m3 for an average apartment and 217 m3 for an average house like ours.

In November 2022, which was warmer than this year, we used 52 m3 of gas for heating. That was less than half the amount used by an average apartment in the Netherlands. This year we substituted 105 kWh of electricity consumed by the heat pump. 105 kWh of electricity is equivalent to the energy released by burning about 10 m3 of gas so we're now heating our four bedroom semi-detached home with about 1/10 of the energy required to heat an apartment.

And the CO2 footprint ? Burning 52 m3 of gas results in the release of 92 kg of CO2. The average gCO2/kWh for the Netherlands in 2022 is 321 g so consuming 105 kWh of electricity results in the release of 33.8 kg of CO2 on average. That's about a third of what we produced last year with gas. But even with the particularly grey weather that we've had for the last month we still generated 1/4 of the electricity that we used from our solar panels (and we used 80% of that directly, not relying on the grid too much as a "battery"), which brings us down to around 25kg, or not far from a quarter of last year. We're signed up to an energy contract which promises "100% green" electricity but while that provides a stimulus for green energy producers it doesn't really change what comes from the grid. I hope of course that we're at least providing a push towards producing greener electricity.

But even in the worst case we're looking at a far lower CO2 output than the 386 kg which an average semi-detached house like ours produced last November.