What would a plug-in solar kit save me?
The short answer
Roughly £60 to £150 a year, depending on where you live and who is home.
Put your postcode in below and it will use the real sunshine figures for your part of the country, rather than a national average. Nothing you type leaves your browser.
Is that figure worth it? That depends on more than the number. See four real households, including the two where the honest answer is no.
How the figures are worked out
Three things decide what a kit is worth to you, and only one of them is the kit.
- Where you live. A south-facing kit in Brighton makes about 1,156 kWh per kilowatt of panel each year. The same kit in Inverness makes about 810. That is a difference of roughly 30 per cent for no other reason than latitude and cloud.
- Where the panels point. A tilted frame facing south does best. Flat on a south wall loses about a quarter. Flat on an east or west wall loses about half.
- Who is home in the day. This is the big one, and the one nobody mentions in adverts. You only save money on power you use while it is being made.
Why being home matters so much
A plug-in kit has no battery and, in almost every case, no export payment. Electricity it makes that you do not use goes into the grid and you get nothing for it. So the kit is worth 26.32p a unit when your fridge, router, freezer and laptop are drawing it, and 0p a unit when the house is empty.
Most homes have a background draw of 150W to 300W all day, which a kit covers easily. Above that, you have to be there to use it. A household with somebody home most days will typically use around half of what the kit makes. A house empty from eight until six will use nearer 30 per cent.
The practical upshot: run the dishwasher, the washing machine and the tumble dryer at lunchtime, not at eleven at night. That single habit can move the saving by £30 a year without spending anything.
What about being paid for the rest?
Normally you are not. The Smart Export Guarantee, the scheme that pays rooftop solar owners for what they send back, requires a certified installation. A kit you plugged in yourself does not have one, so it does not qualify.
There is one exception we have found. Octopus Energy says that if you buy the kit from them and they supply your electricity and you have a working smart meter, you can go onto their Outgoing Prime export tariff. That pays 9p a unit for most of the day and 16p between four and seven in the evening, on a 12-month fixed term. A kit without a battery exports at midday, so 9p is the rate that matters. If you bought the kit anywhere else, Octopus says you cannot sign up for it.
We have not found another supplier offering the same. If you know of one, tell us and we will check it and add it.
Sunshine by city
Units per year for each kilowatt of panel, south-facing on a 35 degree frame. This is what the calculator uses, matched to the nearest city to your postcode.
| Place | kWh per kWp a year | A 930W kit makes about |
|---|---|---|
| Brighton | 1,156 | 1,075 kWh |
| Plymouth | 1,121 | 1,043 kWh |
| Cardiff | 1,042 | 969 kWh |
| Norwich | 1,031 | 959 kWh |
| London | 1,019 | 948 kWh |
| Birmingham | 968 | 900 kWh |
| Leeds | 952 | 885 kWh |
| Newcastle | 947 | 881 kWh |
| Edinburgh | 903 | 840 kWh |
| Aberdeen | 887 | 825 kWh |
| Manchester | 886 | 824 kWh |
| Glasgow | 853 | 793 kWh |
| Inverness | 810 | 753 kWh |
Source: PVGIS 5.3, European Commission Joint Research Centre, queried 26 September 2026. One kilowatt peak, 14 per cent system losses, south-facing at 35 degrees, radiation database PVGIS-SARAH3 covering 2005 to 2023. Unit price: Ofgem price cap, 26.32p per kWh for 1 October to 31 December 2026, single rate, Direct Debit, GB average. Export rates: Octopus Energy, read 26 September 2026.
What the figures do not include
- Shade. A chimney, a tree or next door’s extension can cut output badly, and the calculator cannot know about it. Watch where the shadows fall across a day before you choose a spot.
- The standing charge. A kit reduces the units you buy. It does not touch the daily standing charge, currently 54.83p.
- Your actual tariff. The default is the price cap. If you are on a fixed deal or a time-of-use tariff, type your own rate in. It changes the answer more than anything else on the form.
- Panel ageing. Output drops slowly, usually well under one per cent a year. Over a ten year payback that is a few pounds.
- Inverter clipping. Panels above 800W occasionally make more than the inverter can pass through, and the excess is lost. In UK conditions this is small, but we have not measured it, so we do not pretend to a figure.
Treat the answer as a sensible estimate, not a promise. For context, the government’s own announcement said households could save “up to £110 a year”, and Octopus quotes a range of £50 to £150. Our figures land in the same place, which is reassuring, but every house is different.