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Solar panels save you money in two ways: the electricity you use yourself is electricity you do not buy, and what you do not use can be sold back to your supplier. Whether they are worth it comes down to how those two add up against what the system costs.
A typical 4.5kWp system costs around £7,600 to install, according to Energy Saving Trust estimates reported by Which?, and can generate more than 3,000 kWh a year. In the examples below that pays back in roughly 12 to 22 years, depending on how much you use yourself and the export rate you get.
The two parts of the saving
1. Electricity you use yourself
Every kWh you use from your panels is one you do not buy at your normal rate. Under the energy price cap from 1 October to 31 December 2026 the average electricity unit rate is 26.32p per kWh, so each kWh used at home is worth about 26p.
2. Electricity you export
What you do not use goes back to the grid, and the Smart Export Guarantee means suppliers have to pay you for it. Ofgem does not set the rate. Each supplier chooses its own, and it only has to be above zero, so offers vary a lot. It pays to shop around.
What a typical system saves
Using 3,000 kWh a year from a £7,600 system, at 26.32p for electricity you use yourself:
| You use yourself | Export rate | Saving a year | Simple payback |
|---|---|---|---|
| 30% | 5p | £342 | 22 years |
| 30% | 15p | £552 | 14 years |
| 50% | 5p | £470 | 16 years |
| 50% | 15p | £620 | 12 years |
The share you use yourself and the export rate are example figures. Two things push the saving up: using more of your own electricity, by running appliances in the day or adding a battery, and getting a better export rate.
What changes the answer
- Your roof. A south-facing, unshaded roof generates the most. East or west facing still works, but generates less.
- Where you live. Panels in the south of the UK generate more than in the north.
- Electricity prices. When prices rise, every kWh you use yourself is worth more. When they fall, payback takes longer.
- A battery lets you use more of your own electricity in the evening, but adds to the cost, so it needs its own sums.
- The installer's quote. Prices vary, so get more than one.
Work out your own roof
The solar panel calculator starts from your roof area and works out the system size, the generation, the saving and the payback, including a battery if you are adding one. To see what you spend on electricity now, try the energy bill calculator.
Sources: Which?, Solar panel costs, quoting Energy Saving Trust estimates; Ofgem, Energy price cap unit rates and Smart Export Guarantee. Checked 1 November 2026.
This is general information, not financial or tax advice.
It explains published rules and figures. Your own position depends on your full circumstances,
so speak to a qualified adviser before acting on it.