Google Project Sunroof UK: The Best Alternatives

Every year, thousands of UK homeowners search for “Project Sunroof UK” or “Google solar calculator UK” — and find nothing useful. Google’s Project Sunroof is an impressive tool: it combines satellite imagery, 3D modelling from Google Maps and Google Earth, and local weather data to tell you exactly how much solar energy your roof receives and what a system could save you. The problem is that it only covers the United States and Germany. If you enter a UK postcode, you get no results.

The good news is that the UK has genuinely capable alternatives — and one of them, Solar Wizard, uses the same LiDAR-plus-satellite methodology as Project Sunroof, purpose-built for British roofs.

What Google Project Sunroof actually does

Project Sunroof was launched by Google in 2015 to help US homeowners assess their roof’s solar potential. You enter a US address and the tool uses 3D modelling from Google Maps and Google Earth, combined with local weather patterns and solar irradiance data from the US National Renewable Energy Laboratory (NREL), to calculate how many hours of usable sunlight your roof receives each year. It then estimates system size, installation cost, and long-term savings.

The tool is genuinely clever: it accounts for roof pitch and orientation, nearby buildings and trees that may cause shading, and regional electricity prices to give a personalised estimate. It also surfaces local installer quotes and financing options — all from a single address search.

UK homeowners want exactly this. The frustration is that Project Sunroof has never fully extended its coverage to the UK. A limited pilot ran briefly in a handful of English cities around 2018, but as of 2026 the tool covers only the US and Germany. Enter a British postcode and you get nothing.

Why isn’t the UK covered?

Google has not publicly explained why UK coverage was not expanded after the 2018 pilot. The most likely reason is data availability: the 3D roof modelling that powers Project Sunroof requires high-resolution LiDAR elevation data at national scale, and assembling and licensing that data for the entire UK is a significant undertaking. Google’s focus has remained on its two covered territories.

The practical result is that UK homeowners searching for a Project Sunroof equivalent need to look elsewhere.

The best UK alternatives to Project Sunroof

1. Solar Wizard — the closest UK equivalent

Solar Wizard is the most direct replacement for Project Sunroof in the UK. Developed by the Centre for Sustainable Energy (CSE), a registered charity, it uses the same core methodology: LiDAR elevation data from the Environment Agency and Ordnance Survey is combined with satellite irradiance data to model roof-by-roof solar potential across England, Scotland, and Wales.

Enter your postcode and Solar Wizard identifies your building, analyses each roof plane for orientation, pitch, and overshadowing from nearby structures, and calculates how much electricity a solar system could generate — month by month, not just as an annual average. It then runs a financial model showing estimated bill savings and payback period.

Like Project Sunroof, Solar Wizard is completely free for homeowners. It has been validated against real-world PV installation output data and is used by local authorities across the UK. The data draws from the Environment Agency, MCS, and Ordnance Survey — the same authoritative UK sources a professional installer would use.

Coverage: England, Scotland, and Wales. Northern Ireland is not yet covered.

Best for: Homeowners who want a Project Sunroof-style building-specific estimate without talking to an installer first.
URL: solarwizard.org.uk

2. PVGIS — the technical standard for European solar data

PVGIS (Photovoltaic Geographical Information System) is the reference tool for solar professionals across Europe, operated by the European Commission’s Joint Research Centre (JRC). It is free, requires no registration, and covers the entire UK.

Where Solar Wizard gives you a building-specific estimate, PVGIS asks you to specify your system yourself: enter your location (by map click or coordinates), panel peak power in kilowatts, roof angle (pitch), and orientation (compass direction). PVGIS then draws on the SARAH-3 satellite irradiance dataset — one of the most accurate irradiance models in existence — to calculate annual and monthly electricity yield in kWh, accounting for temperature losses, wiring losses, and inverter efficiency.

It is more technical than Solar Wizard and is aimed at users who already know roughly what system they want. If you’re trying to verify an installer’s generation estimate, or size a system yourself, PVGIS is the tool. Our worked sizing examples in the how many solar panels do I need guide all use PVGIS generation figures.

Best for: Cross-checking installer estimates; sizing a system; users comfortable with a technical interface.
URL: re.jrc.ec.europa.eu/pvg_tools/en/

3. Energy Saving Trust solar calculator — quickest household estimate

The Energy Saving Trust’s solar calculator is the fastest route to a household-level savings estimate. Enter your postcode, the number of people in your home, and whether someone is typically in during the day — and the tool produces an estimate of installation cost, likely bill savings, and export income from the Smart Export Guarantee.

The EST calculator does not perform building-specific roof analysis the way Solar Wizard does; it uses location-based irradiance data and household consumption averages rather than your actual roof geometry. That makes it less precise than Solar Wizard or PVGIS, but considerably quicker if you just want a ballpark before committing time to a more detailed tool.

The EST is a government-funded body, and the calculator is built on UK-specific tariff and consumption data, so the savings figures are realistic for British households.

Best for: A quick first estimate; households who want a number in two minutes without technical input.
URL: pvfitcalculator.energysavingtrust.org.uk

4. Our Solar Planner — personalised to your roof and usage

The Smart Solar Homes Solar Planner takes a different approach to all three tools above. Rather than modelling irradiance at your address from satellite data alone, it walks you through your actual roof, your electricity usage patterns, any plans to add an EV or heat pump, and your goals — and builds a personalised system estimate from the ground up.

If you want to understand not just “how much could my roof generate?” but “what size system makes sense given what I actually use, and what would it cost and save?” — that is the question the Solar Planner is designed to answer.

Which tool should you use?

What to do next

If you want a Project Sunroof-style result for your UK address, start with Solar Wizard. It is free, covers Great Britain, and gives you a building-specific output figure in minutes. Cross-check the generation figure against PVGIS if you want to verify the estimate with a second data source — both draw on satellite irradiance datasets and the results should be broadly consistent.

Once you have a sense of your roof’s potential, the next questions are usually about sizing and shading. Our guide on how many solar panels you need walks through sizing from your electricity bill to a panel count. If your roof has chimneys, trees, or dormers, read our piece on how shading affects solar panel output before talking to an installer — shading losses are one of the most common surprises in UK solar quotes.

When you’re ready for a real quote, get quotes from MCS-certified installers who will survey your roof in person and model the actual shading before recommending a system.