Calculators for your home

Free tools to find out what your home uses, what it costs and what it needs. Every one explains where its numbers come from, and none of them stores your data.

Appliance electricity usage How many kWh each appliance in your home uses, what it costs you each month and which one weighs most on your bill. Calculate → Battery or power station for power cuts What battery, portable power station and inverter you need to keep your appliances running during a power cut. Calculate → How many solar panels you need How many kW of panels and how many panels your home needs from your usage and your city’s sunshine, grid-tied or off-grid. Calculate → Can your power strip take it? Adds up the watts of what you’re plugging in, converts them to amps and tells you if it’s more than your power strip or extension cord can take. Calculate → How much you save with solar panels How much you save per year with solar panels, how many years to pay back the investment and your savings over 30 years. Calculate → What size air conditioner you need What capacity your room’s air conditioner needs from its size, sunshine and people, and how much electricity it will use. Calculate → What your appliances use on standby How many kWh a year, and how much money, your appliances use while off but plugged in, and which weigh the most. Calculate → How much you save with LED bulbs How much you save a year by switching your bulbs to LED, how many months they take to pay off and how many years they last. Calculate →

Built with care

Each calculator uses basic physics and data published by official energy agencies, and cites them so you can check. The results are estimates: they help you make better decisions and ask the electrician or the seller the right questions.

All the maths runs on your own phone or computer. We don’t ask you to sign up and we don’t store what you type.