We had solar panels installed on the roof of our home 13 years ago today. Those panels, which face South-West have been supplemented by additional solar panels facing South/South-East, installed in 2022/2023.
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| Solar power total production in kWh by our rooftop and garage roof panels since their installation in 2012 / 2022. There's still no sign of degradation: Production from the rooftop panels last year was 3% higher than an average year. |
I think it's worth noting that the output of the 13 year old panels on the roof of our home is still as good as it was when they were new. In fact, last year's output was 3% higher than the average over their 13 year life so far. The highest single year output was two years ago when they were already 11 years old. Solar panels do not degrade quickly and unless they are physically damaged it's very unlikely that they need to be replaced.
I increasingly see people selling older solar power systems in order to replace their existing panels with new ones, and I do not understand why they do this. Newer panels do have a higher output than the old ones (e.g. our garage panels are rated over 400 Wp each while the rooftop panels are 270 Wp each), but this is mostly because they are larger. Even if the horrible effect on the environment of disposing of products early is disregarded, I can't believe that the slightly increased output per square metre with newer panels makes it financially viable to swap panels.
I suspect that the large number of single phase older equipment on the second hand market is being driven by a hard sell when people "upgrade" their electrical connection from single phase to three phase. But as it's possible to buy a string inverter for three phases to replace a single phase inverter if so required, it seems likely to me that people are being sold something they don't always need. In my opinion, installing a few extra panels alongside the older ones makes more sense than replacing everything.
When we installed our extra panels on the garage I considered buying second hand panels from one of the people who was for some mysterious reason replacing their existing set, but I couldn't find panels locally with prices low enough to make them attractive. The problem is that even if the panels are local and they have a very low price there are still two things working against them: 1. because they're smaller in capacity you need more material per kWh to mount them (and that costs almost as much as the panels do). 2. you don't know what someone has done with the old panels. Have they been removed from the old roof carefully ? There are too many unknowns.
Cleaning solar panels
I've never tried to clean the solar panels on the roof of our home. They're a long way off the ground and trying to clean them would be dangerous. Nevertheless, their output remains at the same level. My recommendation is that you never clean solar panels installed on a roof. If you try to clean them then you may damage them or injure yourself, and I think it's completely pointless anyway because they self-clean remarkably well each time it rains.
Dynamic tariff effect
The graph above will be less meaningful next year because we now deliberately turn our solar panels off for a few hours on some days to balance the grid. We've already been doing that for almost a month so the graph above is already affected slightly. Unfortunately this will make it more difficult compare the performance of our solar panels each year.
Inverters
As those who read this blog before will know, the ABB inverter for our rooftop panels had a five year warranty and failed after just over six years. The company who made it were absolutely no help at all, offering to do nothing more than sell us a complete new inverter. I took the inverter apart and fixed the problem. The factory soldering was poor, with dry joints which heated up and failed, so I replaced a damaged relay applied new solder. That inverter has now worked for more years since my repair than it did from new. But it's now been in use for 13 years, so I have some concerns about whether something else will fail.
The solar panels on our garage are connected using Hoymiles microinverters. These are only a couple of years old so I would hope they still have a long future ahead of them. Time will tell.
