Energy & Comfort calculators

Watts, kilowatt-hours and your bill

Electricity is billed in kilowatt-hours (kWh): one kilowatt of power used for one hour. An appliance’s wattage multiplied by the hours it runs, divided by 1,000, gives its energy use. Multiply that by your price per kWh and you have its running cost. Rates vary widely between countries and suppliers, so use the unit rate from your own bill where you can; for the US, UK and EU the tools start from a published average with its source and date.

Sizing cooling, not guessing it

An air conditioner that is too small runs constantly; one that is too large cools in short bursts and leaves the air damp. Room size sets the starting point, then sun, insulation, occupancy and kitchens adjust it. In many countries split units are sold by the ton or by kW rather than BTU, so the calculator shows all three.

Solar estimates are a first look

A simple payback figure is useful for deciding whether a solar quote is worth taking further. Real output depends on roof angle, shading and local weather, and savings depend on your tariff and any export payments. Ask installers for a site-specific production estimate before deciding.