Is solar worth it for your home?

What decides payback

The simple payback time is the cost of the system divided by what it saves you each year. If a system costs £7,600 and saves £690 a year, it pays for itself in about 11 years. Panels can last over 20 years (MCS), so the years after that are savings.

1. The cost. Around £7,600 for a typical 4.5kWp system, on the Energy Saving Trust's estimate (Which?, 30 October 2026).
2. How much you use yourself. Each unit you use instead of buying saves the full price: 26.32p per kWh at the Ofgem price cap for 1 October to 31 December 2026.
3. Your export rate. Each unit you send to the grid earns whatever your Smart Export Guarantee tariff pays.

Using more of what you generate

Using your own solar power is worth far more than selling it. In Which?'s worked example, a home where someone was in all day used about 40% of what its panels made. A home that's empty in the day uses less.

A few habits help:

• Run the washing machine and dishwasher in the middle of the day, or set their timers.
• Charge an electric car at home on sunny days if you can.
• Heat your hot water with spare solar, if your system has a diverter.

A home battery takes this further. It stores what you don't use in the day and gives it back in the evening. See how much a home battery costs.

Selling what you don't use

Through the Smart Export Guarantee, larger energy suppliers must offer to pay you for every unit you export, and the rate must be above zero (Ofgem). Fixed rates ran from 1p to 16p per kWh in April 2026 (Which?), so the tariff you pick makes a real difference.

The Smart Export Guarantee explained

Worked examples

Examples A to C are our estimates for a home using 2,700kWh of electricity a year, at 26.32p per kWh, exporting at 16p per kWh. Example D is Which?'s own example.

A to C: 760kWh a year per kWp; the 20% and 70% shares and the battery prices are explained in the calculator's method. D: £295 off bills plus £273 for exports, from 2,850kWh a year (Which?, 23 April 2026).

The export rate matters. If example A were paid 1p per kWh instead of 16p, its saving would fall to about £380 a year. Compare tariffs before you choose one.

Want your own numbers? The payback calculator runs the same sums with your usage, unit rate and export rate.

Sources and dates

We checked every figure on this page on 4 November 2026. If a source changes, we update the page and the date at the top.

1. Solar panel costs, Which?. Page dated 30 October 2026Reports the Energy Saving Trust's estimate that a typical system of about 4.5kWp costs around £7,600 to install, that about 4kWp can make more than 3,000kWh a year, and published battery prices from two large energy suppliers (around £2,500, and from £3,995).
2. Smart Export Guarantee explained, Which?. 23 April 2026 (rates checked April 2026)Fixed SEG rates from 1p to 16p per kWh; the eligibility rules; a worked example of a 3.7kWp system making 2,850kWh a year.
3. Smart Export Guarantee: guidance for electricity suppliers, Ofgem. Viewed 4 November 2026Suppliers with at least 150,000 domestic customers must offer an SEG tariff, and any SEG rate must be above zero.
4. Energy price cap, electricity unit rate 26.32p per kWh, Ofgem. Covers 1 October to 31 December 2026. The next cap is announced on 25 November 2026.
5. A guide to solar panels with Energy Saving Trust, MCS. Updated 20 January 2026Says panels can last over 20 years.

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