How the savings are worked out
Bill saving = generation × share used × electricity price
Export income = generation × share exported × export rate
Payback = cost ÷ yearly saving
The default electricity price is the Ofgem price cap unit rate for 1 October to 31 December 2026 (26.32p per kWh, direct debit, GB average). Export rates under the Smart Export Guarantee vary a lot between suppliers: check what yours pays.
Worked example
A 4 kWp system at 900 kWh per kWp makes about 3,600 kWh a year. Using half of it saves £473.76 on the bill and exporting the other half at 15p earns £270: £743.76 a year. At a cost of £7,000 it pays back in about 9.4 years.
Solar panels on homes are zero-rated for VAT until 31 March 2027. Most domestic installations do not need planning permission, but listed buildings and conservation areas may.
See what your appliances cost to run with the electricity cost calculator.
Frequently asked questions
How much do solar panels save a year in the UK?
A 4 kWp system saves roughly £700 to £800 a year at today's prices if you use about half the power and export the rest.
How long do solar panels take to pay back?
Usually 8 to 12 years, depending on the price, your roof and how much of the power you use yourself.
How much electricity does a 4 kW solar system make in the UK?
About 3,200 to 3,800 kWh a year, depending on where you live and which way the roof faces.
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Last updated October 2026.