Electricity Cost Calculator

When to use it

Every appliance is a small subscription paid through the meter: a fridge that runs all day, a heater that runs for three hours, a console left on overnight. This page turns watts and hours into money, so replacing an old appliance stops being a guess and becomes a comparison.

It estimates running cost, not the whole bill. Standing charges, taxes and tiered tariffs sit outside the calculation, so read the figure as that appliance's share of the bill.

How the maths works

Energy per day = watts × hours ÷ 1,000, in kilowatt-hours. Cost per day = kWh × price per kWh. The headline multiplies the daily cost by 30; the detail lines add the 365-day cost and the yearly energy. Watts are the rating on the label; if only amps are printed, watts = volts × amps.

Most appliances cycle, so their average draw is below the label figure: a fridge compressor switches on and off, and a laptop idles far below its charger's rating. For those, either measure the real consumption or treat the result as an upper bound.

A worked example

A 150 W appliance runs 8 hours a day at 0.30 per kWh, the defaults on the page.

1. Energy: 150 × 8 = 1,200 Wh = 1.2 kWh per day.
2. Daily cost: 1.2 × 0.30 = 0.36.
3. Thirty days: 0.36 × 30 = 10.80.
4. Year: 0.36 × 365 = 131.40, using 438 kWh.

Typical running costs

All at 0.30 per kWh. The heater costs twelve times the fridge for a third of the hours: power matters more than time in this arithmetic.

Common mistakes

• Using the label watts for a cycling device. A fridge rated 150 W may average half that, so the estimate doubles the truth.
• Forgetting to divide by 1,000. Watts times hours gives watt-hours; the price applies to kilowatt-hours.
• Entering more than 24 hours. The page rejects it, because a day has 24 hours and a device cannot run longer.
• Comparing with the whole bill. Standing charges and taxes stay the same whatever you switch off, so compare appliance with appliance.

Keep exploring

• Fuel Cost Calculator — the same cost-per-use arithmetic for a car trip.
• Unit Price Comparison — compare two tariffs or two pack sizes per unit.
• Hourly to Salary Calculator — rate × hours again, this time for your own time.