How do you estimate solar generation?

We use average annual irradiance data for your UK region. A typical 4kW system in southern England generates around 3,800 kWh/year, while the same system in Scotland generates around 3,200 kWh/year.

What electricity price does this use?

We use the current Ofgem price cap rate. You can override this with your actual tariff for a more accurate estimate.

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%+.

5. How much electricity do you use a year?

Check a recent bill, or pick the closest match below.

kWh

UK average is around 3,800 kWh/year

Your estimated annual benefit

£602a year

Over 25 years that's around £15,046 of bill savings and export income from 3,400 kWh of generation a year.

Bill savings

£377 / year

1,530 kWh self-used at 24.67p

SEG export income

£224 / year

1,870 kWh exported at 12p

Total annual benefit

£602 / year

Upfront cost and payback

4 kWp solar system (0% VAT): £6,000
Total upfront: £6,000

Payback period

10.0 years

25-year net return

+£9,046

Like the look of £602 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.

Get free solar quotes

How we worked this out

Energy prices: Ofgem price cap for April-June 2026 (Direct Debit, GB average): electricity 24.67p/kWh. SEG export rate 12p/kWh (Octopus Outgoing rate as of 1 March 2026, previously 15p).

Solar generation: Regional yield based on MCS irradiance data: South England 950, Midlands and Wales 850, North England 800, Scotland 750 kWh per kWp per year (south-facing baseline). 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.