Electricity cost calculator — what an appliance costs to run

How to use the electricity cost calculator

1. Enter the Power rating in watts.
2. Enter the Hours used per day (up to 24).
3. Enter the Number of appliances of that kind.
4. Enter your Price per kWh (unit) and choose the Currency.
5. Set the Days per month (30 by default, up to 31).
6. Read Monthly cost, Daily cost, Yearly cost, Energy per day and Energy per month.

What it does and when to use it

Electricity bills show a total, not what each appliance adds. This calculator lets you price one item at a time: a room heater in winter, an air conditioner in summer, a home office computer, a water pump or a set of light bulbs. It is useful for spotting which appliances cost the most, comparing an old appliance with an efficient replacement, or splitting a bill fairly in shared housing.

To see how quickly a more efficient appliance pays back its higher price, enter the yearly saving into the payback period calculator. For trips by car, the fuel cost calculator does the same job for petrol or diesel. For the electrics behind the wattage, such as working out current from power and voltage, use the Ohm’s law calculator.

How it works

• Energy per day (kWh) = watts × hours per day × number of appliances ÷ 1,000
• Daily cost = energy per day × price per kWh
• Monthly cost = daily cost × days per month
• Energy per month = energy per day × days per month
• Yearly cost = energy per day × 365 × price per kWh

The yearly figure always uses 365 days, so it can differ slightly from 12 times the monthly cost when you set the month to something other than 30.4 days.

Worked examples

These figures come from the calculator’s own function.

A 1,000 W heater for 3 hours a day. At ₹8 a unit over 30 days: energy per day 3 kWh, daily cost ₹24.00, monthly cost ₹720.00, yearly cost ₹8,760.00.

Four 60 W bulbs for 5 hours a day. At £0.30 per kWh: energy per day 1.2 kWh, daily cost £0.36, monthly cost £10.80, yearly cost £131.40.

A 1,500 W air conditioner for 8 hours a day. At ₹7 a unit: 12 kWh a day, 360 kWh a month, monthly cost ₹2,520.00. Because the compressor cycles on and off, the real cost can be lower than this full-power estimate.

Limits and tips

• Rated power is a maximum for many appliances; a plug-in energy meter gives the real figure.
• Standby use of a few watts adds up over 24 hours; run the calculator again with the standby wattage and 24 hours to see it.
• Fixed charges, slabs and taxes on your bill are not modelled.
• All calculation is done in your browser.