There is a lot of talk about solar PV panels these days, some of it positive and a lot of it seems un-informed negative. We’ve had these panels (and more on the roof to the left, not in this photo) since 2011, and they are great! I thought I would give you something of our experience, and maybe debunk some myths.
[EDITS in September 2025.]
This information is based on our personal experience and energy bills, and information from the Internet and other friends who also have panels. As they say, YMMV (“Your Mileage May Vary”) and it’s worth doing your own calculations for your situation. Our panels are not optimally angled, but still we have been producing 10% more than the EST calculator has predicted. And the cost of energy will continue to rise.
What if I don’t have a south-facing roof? Don’t let that put you off investigating. It’s not a matter of all-or-nothing. Ours are south-east and south-west facing, and a too-shallow angle, but they have still been well worthwhile. The Energy Saving Trust has a calculator (or else Solar Wizard) to work out what benefit your particular installation will give you. You can experiment with what it would be *if* it were south facing, and compare to the actual direction. For East and West facing, you may want some on both sides. [EDIT: You would probably only put panels on a north facing roof if it’s a shallow pitch and you are trying to maximise your area and can spare the cash. In Summer, the sun rises in the Northeast and sets in the Northwest. On bright cloudy days the light is diffuse. So don’t get too hung up on facing South.]
How many panels do I need? No doubt a salesman will be happy to advise for your specific circumstances, but we generally think as many as you can fit, in line with what you can afford. There’s a limit on what inverters can send to the grid, without special permissions, so 3-5kW is a reasonable starting point. [EDIT: We have 4kWp of panels and a 3kW inverter.] Whatever electricity you generate but can’t use directly, will be sent off to the National Grid and contribute to the renewable energy available to everyone. [EDIT: many energy suppliers will pay for your surplus solar generation, currently around 15p per kWh, provided you have a Smart Meter and the right tariff.]
How long will they last? Our guarantee is for 25 years, but OF COURSE we won’t replace them then, they will just gradually get a little bit less efficient over time even while they continue to work. 35+ years at least, of worthwhile generation. (We did need to replace the inverter a couple years ago, which was as expected.) [EDIT: modern panels can last 40 years or more, longer than your average uPVC double glazed windows.]
Are they a lot of work to maintain? No, there is nothing at all to do, in our experience. We’ve rinsed them with a hose a couple times, but generally rely on the occasional torrential downpour, or else some snow which cleans as it slides off. We’ve never had to protect them from birds either, though your situation may differ. But it’s a small additional cost for the peace of mind.
I don’t want holes drilled in my roof! Don’t worry, that’s NOT how they are installed. If you are concerned or interested, this video shows the process. Though it’s important to avoid cowboy installers!
What happens to old solar panels? In the UK, we now have a number of companies who dismantle old panels and recycle the materials within. Read about how they do this.
What makes solar panels NOT worthwhile? Probably the biggest negative to consider is if your roof is heavily shaded by trees or buildings most of the time, then you will lose perhaps a third or more of your potential generation. That makes even more difference than facing north. Use the Energy Saving Trust calculator (though the calculator is a bit old) or else Solar Wizard, to work out relative generation. (You can reduce the impact of trees somewhat by individual panel inverters, but you probably don’t want to bother with them otherwise, they add more cost than benefit.)
Do I need a battery? No, you don’t need one. You can choose to time washing the clothes for when the sun is shining, or replace your kettle with a <1kW travel kettle which enables it to need less from the Grid during the day. And whatever you can’t use, the Grid will receive, which benefits the national energy mix. Our panels paid for themselves years ago, but we’re still really glad we got a battery.
[EDIT: with a battery we managed to not use Grid electricity for 6-8 months of the year, and during the rest we charge the battery at a cheaper overnight rate for use during the day. Since we started to be paid for measured export in 2024 via Octopus, we charge the battery overnight all year (7p per unit) to use during the day and save 25p/kWh, and whatever solar we don’t use goes back to the Grid (for 15p per unit income).]
How do I get the most from my solar panels? Everything you generate but don’t use is exported to the Grid, which contributes to the renewable generation for everyone and is a good thing. But what if you want them to earn their keep on your roof?
- Have a diverter to your immersion heater. They are a relatively inexpensive gadget that takes any surplus solar power and sends it to heat the water. If you don’t have a hot water tank, you may want to consider having one installed. We have free hot water from (roughly) mid February to mid October. AND we therefore use less gas, also. [EDIT: if you plan to get paid to export your surplus solar, you may not want a diverter. It may depend on what overnight rate you can get, because you can just heat your water at 7p and export your solar at 15p.]
- Change the way you do things. Running the washing machine or dishwasher during the day, for example, or having a smaller kettle. This requires some creative thinking!
- Get a battery. A battery will allow you to store power you generate during the day, and use it overnight instead. We had an 8kWh battery installed in July 2020, and in the very gloomy August of 2021 our usage from the Grid was 4.1% compared to the previous year; September was 3.3% and October about 12.5%; and November was 50% compared to the previous year. (From December we’re charging the battery overnight at an off-peak rate, and using the stored energy during the day.)
[EDIT – in 2023 we bought an induction hob, and in January 2024 we installed a heat pump, so we are now all-electric. If we were starting with solar again, we would go for a 5kW inverter and a 12kWh battery. But the existing 8kWh battery does us well enough such that a larger one would only save us another £50 per year.]
Finally, new-build houses, as well as being *properly* insulated, are being built with an option on having panels installed. This will reduce electricity bills and potentially give the homeowner an income. Solar panels will be mandated on new builds in 2027. It is unfortunate that some properties only install a token amount, and require you to not get any more from elsewhere.
[EDIT: If you are looking for solar panels, a reasonable starting point is 1 kWp per bedroom, plus 1kWp. so our 3 bed bungalow has 4kWp. More is great, less is still useful, but it’s a ballpark figure to start with. But when builders put just 2kWp on a new build five bedroom house, it may not be worth paying the builders’ premium price.]