Solar payback calculator
Put in your monthly electricity bill and see roughly how long solar panels with a battery would take to pay for themselves. Everything is worked out in your browser. We don't send or store anything.
What if you'd gone solar 10 years ago?
Here's a look back. Imagine a typical home had a 4 kW south-facing system fitted in October 2016 and joined the Feed-in Tariff (FiT). How would it have done by October 2026, compared with not having solar? These are estimates, not real meter readings.
- Cost in 2016: about £6,000 for 4 kW (typical prices then were about £5,000–£7,000).
- Bill savings: about £3,790. That's from using about half the power yourself.
- Feed-in Tariff income: about £2,940. That's the generation payment (4.18p per kWh in late 2016) plus "deemed" export (half your output at 4.91p). Both rise with inflation (RPI) every year, to about 6.5p and 7.6p by 2026.
- Upkeep: about £1,450. That covers cleaning a few times (about £100 each), one electrical check (about £150) and a replacement inverter at about £1,000. Inverters often last 10–12 years, so we've counted one at year 10 to be safe. See looking after your panels for cleaning, checks and bird protection.
- Result after 10 years: savings and income of about £6,730, minus £6,000 to buy and £1,450 upkeep. That leaves you about £720 behind. Without the inverter, you'd be about £280 ahead. The system paid for itself (before upkeep) in its 10th year.
- Still going: the panels should keep working for another 15+ years. FiT payments last 20 years in total, until 2036. So from here on it's roughly £800 a year in your pocket.
- Wear and tear: panels lose about 0.5% of their output each year. Over 10 years that cost about 800 kWh, or roughly £170. That's small. Output in year 10 was still about 96% of year 1.
| Year | Output (kWh) | Average unit price | Bill saving | FiT income | Upkeep | Running total (after £6,000 cost) |
|---|---|---|---|---|---|---|
| Oct 2016–Sep 2017 | 3,600 | 15.0p | £270 | £239 | £0 | -£5,491 |
| 2017–18 | 3,582 | 16.0p | £287 | £250 | £0 | -£4,955 |
| 2018–19 | 3,564 | 17.0p | £303 | £261 | £100 | -£4,491 |
| 2019–20 | 3,546 | 17.5p | £310 | £273 | £0 | -£3,908 |
| 2020–21 | 3,529 | 18.0p | £318 | £285 | £150 | -£3,456 |
| 2021–22 | 3,511 | 21.0p | £369 | £298 | £0 | -£2,789 |
| 2022–23 | 3,493 | 34.0p | £594 | £311 | £100 | -£1,985 |
| 2023–24 | 3,476 | 27.0p | £469 | £325 | £0 | -£1,190 |
| 2024–25 | 3,458 | 24.5p | £424 | £340 | £100 | -£527 |
| 2025–26 | 3,441 | 26.0p | £447 | £355 | £1,000 | -£724 |
The 2022–23 energy crisis made solar worth much more that year. The Energy Price Guarantee capped prices at about 34p per kWh, and the bill saving almost doubled.
How we worked this out
- Output: 900 kWh per kW each year, the same as the calculator above, so 3,600 kWh in year 1, falling by 0.5% a year. The 0.5% figure comes from NREL's study of panel degradation and fits typical 25-year panel warranties.
- Self-use: 50%, with no battery. The other 50% earns the deemed FiT export payment whether you export it or not.
- Unit prices: rough yearly averages (October to September) from Ofgem price cap and government domestic energy price statistics, including VAT. The standing charge is ignored, because solar doesn't change it.
- FiT rates: Ofgem tariff table (0–10 kW, higher rate, 1 Oct–31 Dec 2016), uplifted each year roughly in line with RPI. See Ofgem FiT payments.
- Costs for the install, cleaning, the electrical check and the inverter are typical figures, not quotes. The FiT closed to new homes in 2019. If you install today, you'd use the Smart Export Guarantee instead (see the calculator above).
- We haven't counted the interest the £6,000 could have earned in savings instead.
What if you'd jumped on in 2010?
The very first Feed-in Tariff homes did far better. Here's a rough look at a 4 kW system fitted in April 2010. These are estimates.
- Cost in 2010: about £12,000–£15,000 for 4 kW. Panels were much more expensive back then.
- Generation rate: 41.3p per kWh at the start, paid for 25 years (until March 2035). It goes up with inflation every year. It was linked to RPI until year 17 of the scheme, and to CPI after that. For 2026–27 it's now 76.90p per kWh (Ofgem 2026 tariff table).
- Export: 5.43p per kWh on a "deemed" 50% of what you generate.
- Bill savings come on top. Using your own solar power cuts your bills by roughly a few hundred pounds a year more.
| Estimate | 3,400 kWh a year | 4,000 kWh a year |
|---|---|---|
| Generation payment per year (2026–27) | about £2,615 | about £3,075 |
| Export payment per year (50% at 5.43p) | about £92 | about £109 |
| Still to come, Oct 2026–Mar 2035 (rates flat) | about £22,200 | about £26,100 |
| Still to come, with rises of about 3% a year | about £25,000 | about £29,500 |
| Total generation payments, 2010–2035 | about £55,000 | about £65,000 |
The total assumes an average rate of about 57p per kWh from 2010 to 2026 and ignores panel ageing, so treat it as a rough upper guide.
Why so different from 2016? A 2016 system got just 4.18p per kWh and ended up about £720 behind after upkeep (see above). The rate was cut by about 90% between 2010 and 2016 because panel prices fell sharply, so the government lowered the payments to match.
- You can't get Smart Export Guarantee (SEG) payments while you're being paid for export under the Feed-in Tariff.
- The Feed-in Tariff closed to new applicants on 31 March 2019, so you can't sign up for this today. New systems use the SEG instead (see the calculator above).
- See the full history of rates on Ownergy's rates pages.