Home energy calculators
that show their working
Will a heat pump work here? Is a battery worth it? How long until solar pays for itself? Every one of those answers depends on numbers specific to your house. These tools do that arithmetic in front of you — every step visible, every assumption written down, nothing sent anywhere.
Built by
Vano Gelashvili
Solar & storage
Heating & envelope
Why these are not like the other ones
Most energy calculators online are lead-capture forms wearing a calculator's clothes: they take your postcode and your phone number and hand you back a number you cannot check. These work the opposite way round.
They show every step
Each tool prints its intermediate figures, not just a verdict. If you disagree with the answer you can see exactly which line produced it and change the input behind it.
They publish what they leave out
Every calculator has a section listing its assumptions and its blind spots. The solar tool tells you it ignores inverter replacement. The sizing tool tells you it is not a Manual J.
Nothing leaves your browser
All the arithmetic happens on your device. Nothing you type is transmitted, stored or logged, there is no account, and there is no lead form anywhere on this site.
They deliver bad news
When your payback runs past the warranty, the tool says so in plain language. An insulation upgrade that will never pay for itself gets told that it will never pay for itself.
Built by Vano Gelashvili
Vano Gelashvili is a software developer who builds the calculators on this site. He is not an HVAC engineer, and says so on every page: what he brings is the arithmetic, worked openly against published data.
Found a figure that is wrong? Tell me — corrections are the messages I act on fastest.
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