Solar Savings Calculator UKPayback estimates for real household assumptions

Evidence-backed solar estimate

UK solar panel savings calculator

Start with your quote, then use a known annual generation figure or estimate it from your postcode and roof details. Add household electricity use and tariff choices to calculate bill savings, export income and simple payback.

Want to compare a battery? Complete the solar estimate first. Once your solar-only result is ready, you can add an optional battery comparison using the battery's usable capacity and the extra installed cost of adding it.

Step 1

Your solar quote

Use the installed solar quote, including installation costs.

kWp

Use the rated capacity in kWp shown on the quote or system design. Double-check this is kWp, not watts or the number of panels.

Transparent method

How this UK solar savings estimate works

The calculator splits annual solar generation into electricity used at home and electricity exported to the grid. Self-used electricity is valued at your import unit rate. Exported electricity is valued at your export tariff. The annual benefit is the two numbers added together.

That means a good solar savings estimate needs more than one headline number. A system can look excellent if every kWh is valued at the import rate, but real homes usually export some power. The checker keeps that split visible so you can compare quotes without relying on optimistic sales assumptions.

If you want to audit the arithmetic first, follow the step-by-step solar savings method. For a common system size, the 4kW worked examples show how generation and household use move the result.

Payback is deliberately simple: upfront cost divided by annual benefit. That keeps the result easy to audit. It doesn't assume future tariff inflation, finance costs, maintenance, inverter replacement or panel degradation, so run conservative and optimistic cases before relying on one result.

PVGISEstimate annual generation from postcode, system size, roof direction and pitch, or enter a known annual figure.
2,500 kWhHousehold planning fallback when annual electricity use is not known.
Usage-ledSolar self-consumption is estimated from generation and household electricity use.
4.1pExport planning fallback; use the tariff you can actually access where known.

Useful next checks

What usually improves solar payback?

Solar savings in the UKSee realistic savings examples by system size before running your own numbers.How to calculate solar savingsFollow the generation, self-use, export and payback formula step by step.Solar payback calculatorUse the payback formula and see what makes the number move.Battery vs no batteryCompare extra import savings, displaced export and the incremental battery cost.4kW savings exampleSee how a common UK system changes under conservative and stronger scenarios.Is your roof suitable?Check how roof direction, pitch and shading affect the generation estimate.DNO, G98 and G99Understand the grid paperwork and why inverter capacity matters to a quote.Energy Saving Trust calculator guideCompare the official property-led estimate with your own quote and tariffs.

FAQs

Common questions

How accurate is this solar savings calculator?

It is a transparent estimate based on the assumptions you enter. Real results vary by roof orientation, shading, household usage, installer pricing, inverter performance, tariff changes and metering arrangements.

What electricity unit rate should I use?

Use your actual tariff if you know it. When you choose the calculator's current default, it uses Ofgem's 26.11p/kWh Direct Debit average to 30 September 2026. 26.32p/kWh has been announced from 1 October 2026.

What export rate should I enter?

Use the SEG export tariff you can actually access. Ofgem requires eligible SEG tariffs to be above zero, but suppliers set the rate and contract terms.

Does a battery always improve payback?

No. A battery can reduce grid imports, but it also displaces some export income and adds upfront cost. The current calculator lets you compare one after the solar-only estimate using usable battery capacity and incremental installed battery cost, then shows net annual battery benefit and battery-only simple payback for supported combinations.

How do I calculate solar savings?

Estimate annual generation, split it into the amount used at home and the amount exported, then value each bucket. Self-used kWh are valued at your import unit rate. Exported kWh are valued at your export tariff. Add those two figures for the annual benefit.

Is this a solar savings checker or a final quote?

It is a savings checker and planning estimate. It helps you test a quote, but it can't replace a roof survey, installer design, DNO paperwork or the export tariff terms you can actually access.

Does the calculator include maintenance or inverter replacement?

No. The headline payback uses simple upfront cost divided by annual benefit. For a conservative view, increase the upfront cost or reduce expected annual generation.

Accuracy note

Wider assumptions reviewed 2 July 2026