Free solar calculator

Solar Calculator for UK Homes

Model solar panels, batteries, inverter limits, EV charging, heat pumps, tariffs, import, export, and half-hour usage before you commit to an installation.

Open the free solar calculator Ask Solar Butter to model my home

Calculator comparison

How Solar Butter compares with common calculators

This comparison is based on publicly described features from each calculator. Solar Butter is designed as a whole-home model, so every core modelling field is included.

On a small screen, scroll sideways to see every column.

Calculator	Solar modelling	Battery modelling	Heat pump modelling	Tariff modelling	Import/export breakdown	Hourly / load modelling	Seasonal SOC analysis	Checklist / output
Solar Butter solar calculator	✓	✓	✓	✓	✓	✓	✓	✓
Energy Saving Trust solar panel calculator	✓	×	×	✓	×	×	×	✓
PVGIS	✓	✓	×	×	×	×	✓	✓
Cost-Saver renewable ROI engine	✓	✓	✓	✓	×	×	×	✓
SolarInfo UK solar calculator	✓	✓	×	✓	×	×	×	✓
Solar ROI Calculator UK	✓	✓	×	✓	×	×	×	✓
Solartherm UK solar panel calculator	✓	✓	×	×	×	×	×	✓

Solar Butter solar calculator

Whole-home UK model for solar PV, batteries, inverters, export limits, tariffs, EVs, heat pumps, imports, exports, seasonal battery behaviour, savings, and installation trade-offs.

Energy Saving Trust solar panel calculator

Estimates solar PV system size, bill savings, carbon savings, and possible Smart Export Guarantee payments from property and usage inputs.

PVGIS

European Commission tool for solar radiation, PV yield, grid-connected PV, tracking PV, off-grid PV, monthly data, daily data, hourly data, and TMY data. Its off-grid tool includes battery charge-state outputs.

Cost-Saver renewable ROI engine

Compares solar, battery, heat pump, or mixed upgrades with postcode tariff defaults, editable rates, payback, confidence ranges, and a 25-year outcome.

SolarInfo UK solar calculator

Estimates panels, savings, cost, and payback using region, roof orientation, system size, electricity bill, SEG rate, and optional battery storage.

Solar ROI Calculator UK

Calculates solar payback and ROI with postcode sunshine data, SEG assumptions, battery analysis, projections, and system comparison.

Solartherm UK solar panel calculator

Estimates solar panel cost, battery storage options, bill savings, roof space, and configuration choices for a quote-style journey.

Demo videos

Watch the Solar Butter calculator in action

These short walkthroughs come from the Solar Butter app demo section and show real modelling scenarios you can explore in the calculator.

PV home solar simulation in 60 seconds using the Solar Butter app

A quick tour of modelling a home PV system in the Solar Butter workspace.

Watch on YouTube

Solar and heat pump home system running cost in 60 seconds

A quick look at combined solar and heat pump running costs using the workspace.

Watch on YouTube

Questions

Solar Calculator FAQ

Is the Solar Butter solar calculator free?

Yes. The Solar Butter solar calculator is free to use and does not require sign-up before opening the simulator.

Can the calculator model batteries as well as solar panels?

Yes. It can compare solar PV with different battery sizes, inverter limits, import tariffs, export tariffs, and household demand.

Does the calculator show inverter clipping?

Yes. When PV output in an interval would exceed the inverter AC limit, the model caps how much solar is utilised and counts the rest as clipped generation, so you can compare inverter sizes alongside batteries, load, and tariffs.

Can it estimate solar payback?

The calculator helps estimate bill impact and annual benefit. Payback still depends on the final installed cost and site-specific design.

Evidence