Electricity Cost Calculator

How appliance running cost is calculated

Electricity is billed by energy, not by power. Power is measured in watts, and the energy a device uses is power multiplied by time. The unit on your bill is the kilowatt-hour (kWh), which is 1000 watts running for one hour. To find daily energy, the calculator converts watts to kilowatts by dividing by 1000, then multiplies by the hours used per day: kWh per day = watts ÷ 1000 × hours. Multiplying that energy by your price per kWh gives the daily cost, and the monthly and yearly figures scale up from there.

The formula chain is daily cost = (watts ÷ 1000) × hours × price. For longer periods the tool multiplies the daily cost by 30.44 for a month and 365.25 for a year. Those averages account for months of different lengths and leap years, so the yearly total stays consistent no matter which month you start from. Seeing the per-day, per-month and per-year numbers together makes it easy to judge whether an always-on device, a space heater or a gaming PC is a small or significant share of your bill.

Finding wattage and saving energy

If a device does not list watts, check for volts and amps and multiply them, since watts = volts × amps. Many appliances vary their draw — a fridge cycles on and off, and a heater with a thermostat does not run constantly — so use an average of the hours it is actively drawing power for a realistic estimate. To cut running cost you can reduce hours of use, replace a high-wattage device with an efficient model, or shift usage to a cheaper tariff period if your provider offers one. This calculator runs entirely in your browser; your wattage, usage and pricing figures are never uploaded, and the math uses standard precision suitable for household budgeting.