Solar Panel ROI Calculator
Work out how much solar panels will save you and how long until they pay for themselves.
1. What size system are you considering?
Most UK roofs comfortably fit 4-6 kW. Larger systems need more roof area.
2. Where in the UK is your home?
Southern England gets the most sun. Scotland gets noticeably less.
3. Which way does your roof face?
Pick the closest match. North-facing roofs lose nearly half the output, so payback is much longer.
4. Adding a battery?
A battery stores spare daytime solar to use in the evening, lifting self-consumption from 45% to 75%+.
Check a recent bill, or pick the closest match below.
Your estimated annual benefit
£701a year
Over 25 years that's around £17,522 of bill savings and export income from 3,800 kWh of generation a year.
Bill savings
£450 / year
1,710 kWh self-used at 26.32p
SEG export income
£251 / year
2,090 kWh exported at 12p
Total annual benefit
£701 / year
Upfront cost and payback
- 4 kWp solar system (0% VAT)
- £6,000
- Total upfront
- £6,000
Payback period
8.6 years
25-year net return
+£11,522
Like the look of £701 a year?
These are estimates. The only way to know your real return is a free quote from MCS-certified installers. Takes 2 minutes, no obligation, no pushy sales calls.
How we worked this out
Energy prices: Ofgem price cap for 1 October to 31 December 2026 (Direct Debit, GB average): electricity 26.32p/kWh. SEG export rate 12p/kWh (Octopus Outgoing rate as of 1 March 2026, previously 15p).
Solar generation: Regional yield, south-facing baseline: Midlands and Wales 950, South England 1045, North England 874, Scotland 798 kWh per kWp per year. The Midlands figure is the site-wide one used in every guide. South-east/south-west reduces output by ~5%, east/west by ~15%, north-facing by ~45%.
Self-consumption: 45% of generation without a battery, 75% with a 10 kWh battery (capped at your annual electricity usage). The rest is exported to the grid at the SEG rate.
Install costs: £1,500 per kWp (mid of typical UK ranges, 0% VAT under Energy Saving Materials relief valid until March 2027). 10 kWh battery typically £5,000 installed alongside new solar.
Lifetime:Solar panels carry a 25-year performance warranty and typically last 30+ years; that's our payback horizon. Battery warranties are shorter (10-12 years), so the long-run figures are conservative if the battery needs replacing.
Estimates only. Real-world returns depend on shading, panel quality, inverter performance, your tariff, and how much usage you can shift to daytime. Get an MCS-certified roof survey for a firm quote.