Solar payback by UK region 2026: per-kWp generation and cost data

Solar payback in the UK depends almost entirely on three numbers an installer rarely volunteers together: regional kWh per installed kWp, the export rate the supplier pays under the Smart Export Guarantee, and the install cost per kWp after the zero-rate VAT. Get those three for a specific postcode and the simple payback period falls out of the arithmetic. Most regional quotes hide one of them, usually generation, by quoting a national average.

This piece pulls the three numbers apart by UK region with dated source anchoring.

How "payback" is actually defined in this guide

Payback here is simple payback: the number of years until cumulative annual benefit (self-consumption savings plus export income) equals the upfront install cost net of zero-rate VAT. It does not include discount-rate adjustment, panel degradation (around 0.5% per year), inverter replacement (commonly year 12-15, around £900), or future unit-rate inflation.

Each of those moves the answer, but the simple figure is what most installers quote, so this piece anchors to it for like-for-like comparison.

The three numbers that decide everything

Number one is regional generation, measured in kWh per installed kWp per year. A 4 kWp array in Truro and a 4 kWp array in Inverness do not produce the same electricity in the same year. The Energy Saving Trust's regional generation table, updated for 2025, gives postcode-grouped figures.

Number two is the unit rate of imported grid electricity. Ofgem's April 2026 price cap decision set the typical default-tariff electricity unit rate at around 27p/kWh on direct debit, with regional variation of roughly 2-3p across the 14 distribution zones. Every self-consumed kWh is valued at the local unit rate.

Number three is the export rate. Under the Smart Export Guarantee (SI 2019/1005), every licensed supplier with over 150,000 customers must offer at least one export tariff. Octopus Outgoing Fixed has historically been around 15p/kWh; British Gas Export and Earn 6-15p depending on tariff; OVO Smart Export Tariff around 4p; E.ON Next Export Exclusive around 16.5p for bundle customers; EDF Export plus Earn around 6-12p; Scottish Power Smart Export around 12p; So Energy Export around 6-7p; Good Energy Solar Savings Export around 7-8p. Verify the live p/kWh on the supplier's tariff page before signing.

Regional kWh per kWp: the working table

The 250-300 kWh/kWp spread between the South West top end and Highlands bottom end is the headline regional fact. A 4 kWp array generates roughly 1,200 kWh/year more in Truro than in Wick. At a 27p unit rate that is about £324 a year before export, or roughly £8,100 of cumulative self-consumption value across 25 years.

Install cost benchmarks after zero-rate VAT

HMRC's zero-rate VAT on energy saving materials, extended to retrofitted standalone batteries in February 2024 and running until 31 March 2027 across Great Britain, removed the 5% VAT that previously applied. Installer-side gross margin and component cost still vary regionally and by installer scale, but the post-VAT 2026 benchmarks fall roughly in these bands.

Verify the live quote on the supplier's tariff page or installer scope before signing. Regional cost variance is real: London quotes for the same kit typically come in 8-15% higher than Midlands and Yorkshire quotes, partly because of access surcharges (scaffolding hire in zone 1 versus zone 4) and partly because of higher labour rates.

Worked payback by region: same kit, three postcodes

Set the kit constant: 4 kWp install with a 5.2 kWh battery, £9,200 quoted in April 2026. Set self-consumption at 65% with the battery. Set the export rate at a conservative 8p/kWh blended figure (Octopus Outgoing day-one is higher; the conservative case is what should drive a 10-year model). Set the import unit rate at the April 2026 cap of 27p/kWh.

Truro, TR1, South West. Generation: 3,800 kWh/year. Self-consumed: 2,470 kWh saving £667. Exported: 1,330 kWh earning £106. Annual benefit: £773. Simple payback: roughly 11.9 years. With a higher Octopus Outgoing day-one rate of 15p applied to exports, annual benefit rises to £866 and payback drops to roughly 10.6 years.

Birmingham, B12, Midlands. Generation: 3,400 kWh/year. Self-consumed: 2,210 kWh saving £597. Exported: 1,190 kWh earning £95. Annual benefit: £692. Simple payback: roughly 13.3 years.

Inverness, IV1, Highlands. Generation: 2,900 kWh/year. Self-consumed: 1,885 kWh saving £509. Exported: 1,015 kWh earning £81. Annual benefit: £590. Simple payback: roughly 15.6 years.

The Highlands case is the one most quotes do not run honestly. The catch is that the Home Energy Scotland Grant and Loan, administered by Energy Saving Trust on behalf of the Scottish Government, can offer up to £6,000 grant and £7,500 interest-free loan toward the cost, which can flip the cash-flow picture even though the simple-payback period on net cost still stretches longer than a Truro install.

What changes the answer most: self-consumption rate

Self-consumption is the percentage of generated kWh used in the home rather than exported. Without a battery a typical UK household uses around 30-40% of solar generation in real time. With a 5 kWh battery sized to the property that figure typically rises to 60-70%. Above 10 kWh the marginal gain narrows because winter generation cannot fill it.

The numerical effect on payback is large. A 4 kWp Birmingham array generating 3,400 kWh at 35% self-consumption returns 1,190 kWh of avoided imports (£321) and exports 2,210 kWh (£177 at 8p). Annual benefit: £498. At 65% self-consumption the figures flip to £597 saved and £95 exported. Annual benefit: £692. Same array, same region, same year. The difference is whether a battery is present.

The export-rate question: model the conservative case

SEG export rates are commercial tariffs, not regulated price caps. A buyer modelling 15p on Octopus Outgoing across 25 years is modelling a tariff that is not contractually fixed for that period. Octopus has rolled Outgoing terms forward, but the contract is a 12-month fixed agreement that renews on then-current rates. Building a payback model on the day-one headline rate is the single most common error in installer spreadsheets.

On the ground a 7-8p central case is closer to what the post-2030 export market is likely to deliver as more rooftops crowd the export pool. Wholesale solar capture price during sunny summer half-hours has already fallen below grid import unit rates in some 2025 Elexon settlement periods.

Devolved nation differences: the policy lever

England, Wales and Northern Ireland have no equivalent of the Home Energy Scotland Grant and Loan. The Welsh Nest scheme does not currently fund solar PV. Northern Ireland's Affordable Warmth scheme and the NI Sustainable Energy Programme support insulation rather than solar.

Here is where it breaks for a Welsh household: a Cardiff buyer pays the full quoted price, while an Edinburgh buyer with the same roof can access an interest-free loan that pushes effective payback down on a cash-flow basis even when nominal payback period is longer.

Frequently asked questions

What is the average solar payback period in the UK in 2026?

For a 4 kWp install with a 5 kWh battery on a south-facing roof, simple payback sits at roughly 10-12 years in southern England, 12-14 years in the Midlands and Wales, and 13-16 years in Scotland, depending on self-consumption and the chosen export tariff.

Does generation really vary that much by region?

Yes. Energy Saving Trust regional figures put the South West at 900-1,000 kWh per installed kWp per year and the Scottish Highlands at 700-800 kWh per installed kWp per year. That is a 25-30% spread on the same kit.

Is the zero-rate VAT permanent?

The HMRC zero-rate VAT on energy saving materials runs until 31 March 2027 in Great Britain. After that, the rate is currently legislated to revert to 5% unless extended. The Northern Ireland Protocol creates separate VAT treatment for NI installs.

How much does a battery improve payback?

A 5 kWh battery typically lifts self-consumption from around 35% to around 65%, which roughly translates into £150-£250 more annual benefit on a 4 kWp array in the Midlands. The battery cost of £2,500-£4,000 still adds 3-5 years to nominal payback but shortens the effective payback once full lifetime is modelled.

What is the safest export rate to model?

A blended 7-8p/kWh is a reasonable conservative central case for a 10-year horizon. Modelling at 15p/kWh assumes Octopus Outgoing Fixed stays at its current level for the full payback period, which is not contractually guaranteed.

Do Scottish installs qualify for anything English ones do not?

The Home Energy Scotland Grant and Loan scheme offers up to £6,000 grant and £7,500 interest-free loan for solar PV at qualifying properties in Scotland. England and Wales have no direct equivalent. Northern Ireland has neither.

Sources