Why this exists
Most solar calculators have one of three problems. They are lead-generation forms wearing a calculator costume, and the "result" is a sales call. They are tied to a mapping service that only covers a handful of wealthy countries. Or they hide their assumptions, so you cannot tell whether the generous payback figure comes from the physics or from the marketing.
This site is the opposite of all three. There is no form, no account, and nothing stored. It works at any coordinate on earth because it uses NASA's global satellite record rather than a roof-imagery service. And every formula and constant it uses is published on the methodology page, so you can check our arithmetic and tell us when it is wrong.
Who it is for
Homeowners deciding whether solar is worth it, people sanity-checking a quote they have been given, students learning how PV sizing works, and installers who want a quick second opinion before a site visit. It is deliberately useful in places that are underserved by the big tools — South Asia, the Gulf, Africa, Latin America — where the grid is expensive or unreliable and the case for solar is strongest.
Editorial standards
- We publish our assumptions. Every constant is on the methodology page with its source or its reasoning. Where we simplify, we say that we are simplifying and why.
- We do not sell anything, and nobody pays for placement. We recommend no installer, no brand and no product. If we ever take sponsorship, it will be labelled on the page it appears on.
- We flag uncertainty rather than hiding it. When the irradiance fetch fails and we fall back to an estimate, the page says so in red. When a figure is a rough regional default rather than a researched number, it says that too.
- We correct errors. If a formula is wrong, we fix it and note the change.
How this is funded
By advertising, shown through Google AdSense. That is the whole business model. Ads are placed so they never sit between you and the result — the calculator always comes first on the page, and we do not use interstitials, pop-ups, or ads that push the content down as they load.
We take no commission from installers and run no referral scheme, because the moment a calculator earns money from recommending a bigger system, you can no longer trust its sizing. See the privacy policy for what advertising cookies do.
Data sources
- Solar irradiance and temperature: NASA POWER, monthly climatology, Renewable Energy community.
- Map tiles and search: OpenStreetMap contributors, via Nominatim for place lookup.
We are grateful to both projects. Neither endorses this site.
What we are not
We are not engineers inspecting your roof, we are not electricians, and we are not financial advisers. This site produces estimates for learning and for comparison. Before you spend money, get a site survey and a written quote from a licensed installer, and have the payback checked against your real tariff schedule.