Choose your country and evidence
Select the regional version for the appropriate language, currency and examples. This does not locate your home or identify your supplier. Find the wattage on a device label, a measured energy reading or the relevant figure in its product documentation. For a thermostat-controlled device, measured kWh over a representative period are usually more useful than its maximum wattage.
Enter realistic use and prices
Check whether a field expects W, kW, kWh or a percentage. Use your actual running time and the unit price applicable to that usage. A monthly fixed charge is not a price per kWh. Replace the suggested values when you have better information and read any explanation about charging losses, operating days or annual averages.
Read and compare the outcome
Review the energy result before the cost result: changing a tariff changes cost, not consumption. Try one alternative at a time to see what drives the difference. Consult the formula and assumptions, then use related tools for the next question. Calculations remain in the browser; note your values before leaving or reloading the page.