Which electricity tariff makes plug-in solar pay back fastest?
The short answer
The one that charges you most for daytime electricity.
A plug-in kit saves you whatever you would have paid for each unit it covers, at the moment it makes it. That is almost always daytime. So what matters is your daytime unit rate, not your night rate or your headline price. On most tariffs, nothing is paid for what you send to the grid.
We do not sell energy and are not paid by any supplier. This page explains how each kind of tariff changes what a kit is worth, using the Ofgem price cap and the European Commission’s solar model, PVGIS. It does not tell you to switch: for most households the kit is too small a part of the bill to choose a tariff around it.
How a kit saves money
A kit without a battery has one way to save you money: every unit it makes that your home uses at that moment is a unit you do not buy. Each one is worth exactly the unit rate you would have paid. Electricity it makes while nothing in the house is using it goes to the grid, and on almost every tariff you are paid nothing for it.
So the saving is units used at home, multiplied by your unit rate at that time. A two-panel 930W kit in London makes about 948 kWh a year facing south. If 40% of that is used at home, that is about 379 units. Every 1p on your unit rate changes the saving by about £3.79 a year. At the price cap rate of 26.32p, the saving is about £100.
Single-rate tariffs
Most homes pay one unit rate all day. This is the simplest case: every unit the kit covers saves that rate. The Ofgem price cap average for England, Scotland and Wales from 1 October to 31 December 2026 is 26.32p per kWh by Direct Debit, and it varies by region. Our savings calculator uses that figure, and you can change it to your own rate.
A fixed deal works the same way, at its own rate. If yours is below the cap, your kit saves a little less than our figures; if it is above, a little more.
Economy 7 and other two-rate tariffs
On Economy 7 you pay one rate during peak hours and a cheaper one during off-peak hours, usually overnight. Ofgem says the two together cannot be more than the price cap. A kit makes almost nothing at night: on PVGIS hourly figures for London, a south-facing kit makes about 0.2% of its year between midnight and 7am.
That means nearly every unit your kit covers is saved at your peak, daytime rate. Look at your bill for the rate that applies during the day, and use that in the calculator rather than an average. If you run the washing machine and dishwasher overnight to use the cheap rate, think before moving them to midday. On bright days the kit covers them; on dull days you would pay the day rate for them instead of the night rate.
Tariffs with an expensive late afternoon
Some time-of-use tariffs charge more between about 4pm and 7pm. A kit facing south makes most of its power around midday, so it does little at those hours. One facing west makes much more of its power late in the day. This is from four years of hourly PVGIS figures for London:
| Where the panels face | Made a year, per kWp | Made 4pm to 7pm | Share of the year |
|---|---|---|---|
| South, tilted frame | 1,023 kWh | 140 kWh | 14% |
| West, tilted frame | 794 kWh | 203 kWh | 26% |
| East, tilted frame | 828 kWh | 61 kWh | 7% |
| Upright on a south wall | 735 kWh | 78 kWh | 11% |
| Upright on a west wall | 499 kWh | 190 kWh | 38% |
PVGIS 5.3, European Commission Joint Research Centre, hourly output for 2020 to 2023 at London (51.507 N, 0.128 W), 1 kWp, 14% system losses, queried 7 October 2026. Hours are UK clock time, including British Summer Time. Averaged over the four years, so the yearly totals differ slightly from the long-term averages on our other pages.
A west-facing tilted frame makes less over the year than a south-facing one, but more in the late afternoon. For a 930W kit that is about 189 kWh a year between 4pm and 7pm facing west, against about 130 facing south. If you are home to use it, every 1p your tariff adds to the late-afternoon rate is worth about £1.89 a year to a west-facing kit and about £1.30 to a south-facing one. Whether west comes out ahead overall depends on how much more your tariff charges at those hours. For which way your panels can face, see which way plug-in solar panels should face.
Time-of-use tariffs generally need a smart meter, so the supplier knows when you used each unit.
Being paid for what you export
Usually you are not. The Smart Export Guarantee requires some suppliers to pay small generators for electricity they send to the grid, but Ofgem’s guidance for generators says solar installations up to 50kW must show that both the installation and the installer are suitably certified, and must have an export meter. A kit you plug in yourself does not have a certified installer.
The same guidance says a supplier that is not obliged to pay may still choose to. We have found one supplier offering an export tariff for plug-in kits, with conditions: the details are on our savings calculator page. Because a kit without a battery exports at midday, the midday export rate is the one that counts.
What to check on your bill
- Your daytime unit rate. This is the number that decides your saving. Put it in the calculator.
- Whether you have more than one rate. If your bill shows a day and night rate, or a peak window, the daytime or peak rate is the one your kit saves.
- When your deal ends. A fixed rate that ends soon may be replaced by a different one, and the saving moves with it.
- Whether you have a smart meter. You need one for time-of-use and export tariffs.
Questions people ask
Does plug-in solar work with Economy 7?
Yes. The kit makes power during the day, so it saves you your daytime rate on whatever it covers. It makes almost nothing in the cheap overnight hours, so the night rate does not affect its saving.
Should I change tariff because I have a plug-in kit?
Usually not for the kit alone. A typical kit saves roughly £60 to £150 a year, while your tariff affects every unit you buy. Choose the tariff that suits your whole home, then work out what the kit saves on it.
Can I get the Smart Export Guarantee with a plug-in kit?
Normally no. Ofgem’s guidance says solar installations up to 50kW need a certified installation and a certified installer to qualify. A supplier may still choose to pay for export from a plug-in kit, but it does not have to.
Sources, read 7 October 2026: Ofgem, energy price cap unit rates and standing charges (26.32p per kWh, 1 October to 31 December 2026; how multi-rate tariffs work under the cap); Ofgem, Smart Export Guarantee: guidance for generators (paragraphs 1.7 and 1.12 to 1.16). Hourly and yearly output from PVGIS 5.3. Savings assume a 930W kit with 40% of its output used at home.