Solar panel payback calculator
When does a solar system pay for itself? Enter what you were quoted, and see the payback year, the annual saving, and a 25-year cumulative table at today’s energy prices.
Figures checked October 2026 Estimate
Assumes ~850kWh/kWp/year (estimate), flat energy prices and no panel degradation. Rising prices shorten real payback; the savings estimator models 3%/year price growth.
How solar payback works
Every unit your panels generate is worth money one of two ways. Use it yourself and it’s worth the full import price — 26.32p/kWh at the October–December 2026 price cap. Export it and the Smart Export Guarantee pays an estimated 3–6p/kWh on a standalone tariff. That gap is the whole game: a 4kWp system generating an estimated 3,400kWh a year saves roughly £460 a year at 40% self-consumption, and £600+ at 70% with a battery. Divide your install cost by the annual saving and you have the payback period — for most well-sited UK systems at 2026 prices, an estimated 10–15 years at typical self-consumption — nearer 10 with a battery — on panels warrantied for 25.
Self-consumption is the lever you control. Timers on the dishwasher and washing machine, charging an EV at midday, heating water with surplus solar — all push generation from the 5p bucket into the 26p bucket. A battery does it automatically, which is why battery systems show faster payback in this calculator despite costing more: try 40% versus 70% and watch both figures move.
What the simple payback figure leaves out
Three honest caveats. Energy prices: this calculator holds them flat, but if prices rise (they have, historically), payback shortens — the savings estimator shows the 3%-inflation version. Degradation: panels lose roughly 0.5% of output a year (estimate), which barely moves the answer. And the inverter swap at year 10–15 (an estimated £800–£1,500) is a real cost worth mentally adding. Even with all three, a good roof at 2026 prices is comfortably in profit over 25 years — the average case works out in our worth-it guide.
Payback questions
What payback period should I accept?
Under 10 years is strong at 2026 prices; 10–13 years is normal for east/west roofs or low-usage homes; beyond 15 years, look hard at whether the system is oversized or the quote is too high.
Does payback include the SEG?
Yes — exported electricity is credited at the SEG rate you set. Check your actual tariff: 12–16p/kWh combined import/export deals change the picture significantly versus a 3–6p standalone tariff.
What if electricity prices fall?
Payback stretches. At 20p/kWh a typical system adds roughly two years. That’s the honest risk in any solar purchase — you’re buying a hedge as much as an investment.
Ready for real prices?
Calculators give you the ballpark. Get free, no-obligation quotes from MCS-certified UK installers and compare them against these numbers.