How many solar panels does a UK home need?

A typical UK semi-detached home using 3,500–4,500 kWh/year needs 10–14 panels (4–5.5 kW system) in southern England, or 12–16 panels in Scotland. The lower sun hours in the UK compared to Australia or the US mean you need more panels per kWh of consumption. Enter your annual bill for a precise calculation.

How much does solar save on UK electricity bills?

A 4 kW system in southern England produces around 3,400 kWh/year. If you self-consume 50% and export 50% at 6p SEG: savings = 1,700 kWh × 24p = £408, plus SEG income of 1,700 kWh × 6p = £102. Total annual benefit: ~£510. With a battery boosting self-consumption to 80%, total annual benefit rises to ~£680.

What is the Smart Export Guarantee (SEG)?

The SEG is the UK government scheme that replaced the Feed-in Tariff in 2020. Large electricity suppliers must offer you a payment for any solar electricity you export to the grid. Unlike the old FIT, there is no guaranteed minimum rate — suppliers set their own rates (typically 4–15p/kWh in 2026). Octopus Outgoing offers the highest variable rates, tracking wholesale prices.

Solar Calculator UK

How many solar panels does your UK home need? Enter your electricity bill and city — get system size, panel count, annual savings, and SEG income.

Your electricity usage

Annual electricity bill?

Electricity unit rate?

£/kWh

City / location?

Panel wattage?

Self-consumption?

SEG export rate?

£/kWh

Recommended system

8 kW (20 panels)

Annual production5,840 kWh/year

Annual bill savings£701/year

SEG income£175/year

Total annual benefit£876/year

Peak sun hours2.5 hrs/day (Manchester)

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How to Use This Calculator

Enter your annual electricity bill and rate

Enter your annual electricity bill in GBP (total for 12 months). Check your online energy account or paper bills. If you only have a monthly figure, multiply by 12. The unit rate is the pence-per-kWh charge on your bill (not the standing charge). In 2026 under the price cap, the typical unit rate is around 24p/kWh — but check your actual bill for the rate you pay.

Select your city

Your location determines peak sun hours — the equivalent hours of full-strength sunlight per day. The UK ranges from 3.1 hours in Brighton down to 2.2 hours in Aberdeen. Southern England generates significantly more solar energy than Scotland or Northern Ireland. This single factor has the biggest impact on system sizing after your electricity consumption.

Self-consumption and SEG rate

Expand More options to adjust self-consumption percentage and your Smart Export Guarantee (SEG) rate. Self-consumption is the proportion of solar you use directly in your home (rather than exporting). A home where occupants are present during the day achieves 50–70%; an empty house during work hours might be 25–35%. Adding a battery increases self-consumption to 80–90%.

The Formula

Annual kWh = Annual bill (£) ÷ Unit rate (£/kWh) Daily kWh = Annual kWh ÷ 365 System kW = Daily kWh ÷ (Peak sun hours × 0.80 efficiency) Panel count = System kW × 1000 ÷ Panel wattage (W) Annual production = System kW × PSH × 0.80 × 365 Annual savings = Self-consumed kWh × Unit rate SEG income = Exported kWh × SEG rate Total benefit = Annual savings + SEG income

The 80% system efficiency factor accounts for UK-specific losses: high-temperature coefficient losses in summer, shading from chimneys and neighbouring buildings, inverter conversion losses, and wiring resistance. UK installations also often face suboptimal roof angles — the calculator assumes a typical south-facing 30–40° pitch.

Example: Manchester Semi-Detached

3-bedroom semi, family of 4, Manchester

Annual electricity bill £1,400, unit rate 24p/kWh, 2.5 peak sun hours/day, 50% self-consumption, SEG rate 6p/kWh.

Annual bill£1,400

Unit rate24p/kWh

Annual consumption5,833 kWh

Peak sun hours2.5 hrs/day (Manchester)

Result

System size~5.5 kW

Panel count14 x 400W panels

Annual production~4,015 kWh/year

Annual bill savings~£482/year

SEG income~£121/year

Total annual benefit~£603/year

At £6,000–£7,000 installed cost for a 5.5 kW system, payback is approximately 10–12 years — longer than sunnier climates but still a solid investment given rising electricity prices and a 25-year panel lifetime. Adding a battery reduces the payback slightly but increases daily self-sufficiency.

Smart Export Guarantee (SEG)

The Smart Export Guarantee replaced the old Feed-in Tariff (FIT) scheme in January 2020. Under SEG, electricity suppliers with 150,000+ customers must offer an export tariff — but they set their own rates (minimum is above 0p/kWh). In 2026, typical SEG rates are:

Octopus Energy Outgoing: Dynamic rate tracking wholesale prices, typically 4–20p/kWh
British Gas: 5.5p/kWh
OVO Energy: 4p/kWh
E.ON: 4.1p/kWh
EDF: 4p/kWh

Because SEG rates (4–15p/kWh) are much lower than the retail rate you pay (24p/kWh), maximising self-consumption — or adding a battery to store solar for evening use — is more economical than maximising exports.

FAQ

Is solar worth it in the UK in 2026? ▼

Yes — the combination of high electricity prices (24p/kWh+), falling solar panel costs, and the SEG export tariff makes solar a good investment for most UK homeowners. Payback periods range from 8–14 years in the UK (versus 5–8 years in sunnier countries), but with a 25-year panel warranty, you get 11–17 years of free electricity after payback. Rising electricity prices will shorten payback over time.

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

Most residential solar installations in England, Wales, and Scotland fall under Permitted Development Rights, meaning no planning permission is required. Exceptions include: listed buildings (Grade I or II), homes in conservation areas (panels must not be visible from the highway), and properties where permitted development rights have been removed. Always check with your local planning authority if unsure.

What is a typical UK solar installation cost? ▼

In 2026, typical installed costs for UK solar: 3–4 kW: £5,000–£7,000. 5–6 kW: £6,500–£9,000. 8–10 kW: £9,000–£13,000. Battery storage (10 kWh): add £2,500–£4,000. Get 3+ quotes from MCS-certified installers. Installation costs include panels, inverter, mounting hardware, cabling, DNO notification, and commissioning. VAT on residential solar is 0% in the UK since April 2022.

How many solar panels fit on a UK house roof? ▼

A typical UK semi-detached has about 20–30 m² of usable south-facing roof space, fitting 8–12 panels (3.2–4.8 kW). A larger detached home might fit 14–20 panels (5.6–8 kW). Each 400W panel needs about 1.7–1.8 m². Your installer will survey roof space, orientation, shading from chimneys and neighbouring buildings, and structural suitability. East-west split arrays are an option for homes without south-facing roof space.