Electricity Cost Calculator

Written byOleh Soloninupdated 5 October 2026

Appliance power, W

Hours per day

Days per month

Tariff per kWh

Result

kWh per day6
kWh per month180
kWh over 12 such months2,160
Cost per day$36.00
Cost per month$1,080.00
Cost over 12 such months$12,960.00

Watts, hours and your tariff

Consumption in kilowatt-hours and in money per day, month and year from an appliance's rating and running time.

Your meter counts kilowatt-hours: a thousand watts for an hour. So an appliance's consumption is its power in kilowatts times the hours it runs, and the cost is those kilowatt-hours times your tariff. A 1,500 W heater running four hours uses 6 kWh a day and 180 kWh a month — 1,080 at a tariff of 6.

The figure on the rating plate is a maximum. Anything with a thermostat — a fridge, a water heater, a heater with a dial — spends much of its time idle, so it uses less. For those, enter the hours it actually runs rather than the hours it is switched on.

How to use

Enter the appliance's power in watts — from the rating plate, the manual or a plug-in meter.
Enter the hours a day it runs and the days in the month.
Enter your price per kWh.
Read the energy and cost per day, month and year.

What different loads use

The power and hours in each row are inputs for the sum, not ratings of particular appliances: put in your own. Each row is a separate run of the calculator over 30 days at a tariff of 6.

Every row comes from the calculator on this page.
Load	Power	Hours a day	kWh a month	Cost a month
Heater	1500 W	4	180	1,080
Kettle	2000 W	0.5	30	180
Constant load	100 W	24	72	432
LED bulb	10 W	5	1.5	9
EV wall box	7000 W	5	1,050	6,300

What this calculator shows

Energy in kilowatt-hours per day, month and year
The same periods in money at your tariff
An annual figure that makes appliances easy to compare

What to keep in mind

The appliance is taken to run at full power for all the hours entered; if it cycles on a thermostat, enter its real running time.
The tariff is yours — it depends on where you live, your supplier and, on a time-of-use meter, the time of day.

FAQs

What is a kilowatt-hour?

The energy a one-kilowatt appliance uses in an hour. It is exactly what the meter counts, and the tariff is its price.

How do I turn watts into kilowatt-hours?

Divide the watts by 1,000 and multiply by the hours. 1,500 W × 4 h = 6 kWh; a 10 W bulb for 5 hours is 0.05 kWh.

How do I cost an appliance that switches itself on and off?

Fridges, water heaters and thermostatic heaters run in cycles. If the manual gives a daily consumption, divide it by the power to get the running hours; otherwise a plug-in meter over a day is the most accurate way.

What does a constant 100 W cost?

Around the clock it is 2.4 kWh a day and 72 kWh in a 30-day month. Twelve such months come to 864 kWh; a full 365-day year, to 876. At a tariff of 6 that is 432 a month and 5,184 over the twelve months.

How much does charging an electric car at home use?

A 7 kW wall box for five hours a day is 35 kWh, or 1,050 kWh and 6,300 a month at a tariff of 6. The EV charging calculator is more precise: it works from the battery size and allows for losses.

How do I compare two appliances?

By the annual line at the same usage: it shows what each costs a year. The extra purchase price divided by the annual saving gives the payback time of the thriftier one, in years.

Worked example

A 1.5 kW heater

Input: 1500 W, 4 hours a day, 30 days, tariff 6

Output: 180 kWh a month, 1,080

Note: That is 6 kWh and 36 a day, and 2,160 kWh and 12,960 over twelve such months. A 2,000 W kettle used half an hour a day takes 30 kWh in the same month — a sixth as much.

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Result

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