How much electricity do solar panels generate in the UK?

UK solar panels generate less than those in sunnier climates due to lower irradiance and more cloud cover. A 1 kWp (kilowatt-peak) system typically generates 850–1,000 kWh per year in the UK, varying by location (Cornwall gets more than Scotland), pitch, and orientation. A south-facing 30° pitch is optimal. This calculator uses 900 kWh per kWp as a UK average.

What is the Smart Export Guarantee (SEG)?

The Smart Export Guarantee (SEG) is a government scheme that requires electricity suppliers to pay homeowners for surplus solar electricity exported to the grid. SEG tariffs vary by supplier, typical rates range from 4p to 15p per kWh in 2026. The best SEG tariffs are from energy companies such as Octopus Energy and OVO Energy. You need a smart meter to receive SEG payments.

How much can I save on energy bills with solar panels?

Annual savings depend on your system size, electricity consumption, electricity tariff, and how much solar energy you use vs. export. At Ofgem's October 2025 price cap rate of approximately 24p/kWh, a 4 kWp system generating 3,600 kWh/year could save £576–£864 in direct usage savings, plus SEG export payments. Typical total savings are £500–£1,200 per year.

How long do solar panels take to pay back in the UK?

The payback period for a typical UK solar installation (4 kWp, cost ~£6,000–£9,000) is typically 7–12 years, depending on electricity prices, SEG rates, and self-consumption. With high electricity prices (24p+/kWh) and a good SEG tariff, payback can be under 8 years. Solar panels typically have a 25-year performance warranty.

Do I need planning permission for solar panels in the UK?

In most cases, no, solar panels are permitted development in England, Wales, and Scotland under certain conditions (not more than 200mm above the roof plane, not higher than the highest part of the roof excluding chimneys). Listed buildings and properties in conservation areas may need permission. Always check with your local planning authority before installing.

Updated 1 May 2026

Solar Panel Calculator · Free UK Cost & Savings 2026

Estimate how many solar panels you need, your annual kWh output, and bill savings including Smart Export Guarantee (SEG) payments.

✓ Free to use✓ Panels / output / savings✓ SEG included✓ Instant estimate

Solar Panel Calculator

Choose a mode and enter your values. Results appear instantly

Annual electricity usage (kWh)

Panels needed

9 panels

3.60 kWp system, ~3240 kWh/year output

Annual usage

3000 kWh

Panel rating

400W

UK irradiance

900 kWh/kWp

Panels needed

System size

3.60 kWp

Est. annual output

3240 kWh

Estimates based on UK average irradiance (900 kWh/kWp). Output varies by location, roof pitch, and shading. Not a formal energy assessment.

How the Solar Panel Calculator Works

Quick Answer: A typical UK 4 kWp solar system (10 × 400W panels) generates approximately 3,600 kWh/year and could save £600–£900/year on electricity bills at 24p/kWh, plus SEG export payments. Payback is typically 7–12 years on a £6,000–£9,000 installation.

UK Solar Calculation Assumptions

This calculator uses the following UK-specific assumptions: panel rating 400W; UK annual irradiance 900 kWh per kWp; electricity price 24p/kWh (Ofgem price cap, October 2025 quarter); SEG export rate 7p/kWh (indicative mid-range); self-consumption 50% of generated electricity. Adjust the electricity rate in the savings mode if your tariff differs.

Formula

Panels needed = Annual usage (kWh) ÷ (panel kW × 900 UK sun hours)

e.g. 3,000 kWh ÷ (0.4 kW × 900 hrs) = 8.3 panels → 9 panels

Worked Example: 3,000 kWh usage, 400W panels

Annual electricity usage3,000 kWh

Panel rating400W (0.4 kW)

UK sun hours900 kWh/kWp

Panels needed8.3 → 9 panels

System size3.6 kWp

Annual output3,240 kWh

Annual savings (24p/kWh)~£389 usage + SEG

Actual output varies by location, roof pitch, orientation, and shading. South-facing 30° pitch is optimal.

Frequently Asked Questions

A typical UK home uses around 2,700–3,100 kWh of electricity per year. With an average UK panel rated at 400W and around 850–1,000 peak sun hours per year, each panel produces approximately 340–400 kWh/year. A typical 3-bedroom home needs 6–10 panels (a 2.5–4 kWp system). This calculator estimates the number of panels based on your annual electricity usage.