UK solar panel size, cost and payback calculator

☀ Your electricity use and roof

Current annual electricity use

kWh/year

Use the total from your latest 12 months of electricity bills or supplier account.

Planning higher electricity use?🚗Electric car+2 500 kWh♨Heat pump+3 500 kWh

UK location

Imported electricity price

£/kWh

Panel directionSouth · 100 %

Roof or panel pitch35°

0° flat35° typical optimum90° wall

Installed system price

£/kW

Power per panel

Editable UK starting points: £0.26/kWh imported electricity and £1,450 per installed kW. Replace both with your tariff and installer quote.

Include a possible grantNo single UK-wide solar grant applies to every household

Grant amount

Enter only a grant or local scheme for which your home is eligible. Keep this at £0 if none applies.

Self-use and export tariffSmart Export Guarantee (SEG)

Share used directly in the home35 %

Electricity used while the panels are generating, before it reaches the grid.

Export arrangement

Export payment

£/kWh

SEG suppliers set their own tariff. Enter the rate offered by your supplier.

▣ Your solar estimate

Recommended system size——

Annual electricity coverage—

—

Net investment——

Annual generation——

Simple payback——

25-year net benefit—benefit after installation cost

Cost before grant—

First-year benefit—

Used directly—

—

How much could the panels generate each month?

A typical UK monthly profile compared with your modelled consumption. Hover over or tap a bar.

generationuse

This is a climate profile, not a weather forecast. Shading, local weather, inverter limits and downtime can change actual output.

Would a smaller or larger system make more sense?

Compare three nearby sizes using the same roof, tariff and cost assumptions.

Cost comparison for 4 kW, 8 kW and 12 kW solar systems

The table uses your installed price per kW and grant amount.

System size	Approx. panel count	Before grant	Grant	Estimated cost

ƒx

Method: annual demand is divided by output per kW adjusted for region, direction and pitch. Financial value combines electricity used on site with export income under the selected tariff.

How to estimate solar panel size and payback

Four inputs turn a generic solar estimate into a useful household scenario.

Use a full year

Enter 12 months of electricity use and include an EV or heat pump only if it is genuinely planned.

Describe the roof

Choose the closest UK region, panel direction and pitch. These change annual output per kW.

Use your real prices

Replace the examples with your electricity tariff, SEG export rate and a VAT-inclusive installer quote.

Compare scenarios

Review system size, roof area, monthly output, upfront cost and simple payback together.

How many solar panels does a UK home need?

Solar panel cost, SEG income and payback in the UK

Installed price

The default is an editable market starting point, not a quotation. Enter the total installed quote divided by system kW.

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Solar yield

Southern England generally receives more solar energy than Scotland, but roof direction and shading can matter just as much.

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Smart Export Guarantee

SEG pays for metered electricity exported to the grid. Suppliers set their own rates and conditions, so use the tariff actually available to you.

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Self-consumption

Electricity used directly avoids the full import price and is often worth more than exported electricity. Timers, EV charging and a battery can change this share.

Data sources and limitations

The regional yield assumptions are broad planning values. Check a precise postcode and roof configuration with the European Commission’s PVGIS tool. Smart Export Guarantee rules and current participating suppliers are described by Ofgem.

This calculator gives an indicative energy and cash-flow model, not an MCS quotation, structural survey, tax calculation or DNO approval. Prices, export tariffs, grants and eligibility can change; verify them before committing.

Frequently asked questions about solar panels in the UK

Practical answers for comparing a domestic solar PV proposal.

How many solar panels do I need for 3,600 kWh a year?

With 450 W panels, a favourable roof may need roughly nine or ten panels, giving around 4.05–4.5 kW. A northern location, east–west roof or shading can increase the required size.

How much electricity does 1 kW of solar produce in the UK?

A useful planning range is about 800–1,000 kWh per year, with higher output generally in southern England and lower output in Scotland. Use PVGIS and a site survey for the address.

What is the Smart Export Guarantee?

SEG requires eligible electricity suppliers in Great Britain to offer a payment for metered renewable electricity exported to the grid. The supplier chooses its tariff and terms.

Does the calculator include VAT and scaffolding?

The price input should be the full installed amount per kW, including VAT, scaffolding and any electrical work in the quote. If those items are excluded, the payback will look too optimistic.

Do solar panels work in winter?

Yes, but winter output is much lower because days are shorter and the sun is lower. Most UK solar generation occurs from spring through early autumn.

Is a battery included?

No. The model covers solar PV only. A battery changes self-consumption, export and project cost and should be assessed separately.

Is the result guaranteed?

No. It is a planning estimate. Weather, shade, equipment, curtailment, degradation, tariff changes and maintenance all affect real performance.