Electricity cost calculator

Electricity cost of running an appliance per hour, day, month and year, from its wattage, hours of use and your price per kWh (unit).

Mis à jour 28 septembre 2026Exemples vérifiés : 5

Cost per month

Décimales : 2 ; Au plus proche, égalités vers le chiffre pair

Cost per year: $324.00
Cost per day of use: $0.90
Cost per hour: $0.2250
Energy per day of use: 6kWh
Energy per month: 180kWh
Energy per year: 2,160kWh

The rated power is a maximum: fridges, ACs and heaters cycle on and off, so their real use is usually lower. Tariffs with slabs, fixed charges or time-of-day rates will differ.

Running it 4 h a day uses 6 kWh per day of use — 180 kWh a month, about $27.00 at $0.150 per kWh, or $324.00 a year.

Monthly cost with the same use (4 h a day, 30 days)

Comment le calcul est effectué S

Power in kilowatts
$P = \frac{1{,}500\ \mathrm{W}\times 1}{1000} = 1.5\ \mathrm{kW}$
Energy per day
$E_{\text{day}} = 1.5\ \mathrm{kW}\times 4\ \mathrm{h} = 6\ \mathrm{kWh}$
Energy per month and year
$E_{\text{month}} = 6\times 30 = 180\ \mathrm{kWh},\quad E_{\text{year}} = 12\times E_{\text{month}} = 2{,}160\ \mathrm{kWh}$
Cost
$\text{cost}_{\text{month}} = 180\times 0.15 = 27,\quad \text{cost}_{\text{year}} = 324$
Money is shown rounded to the currency's minor unit; the year is 12 months of the pattern you entered.

À propos de Electricity cost calculator

The calculator turns an appliance's power rating into energy and money. Energy per day is the power in kilowatts times the hours of use, in kilowatt-hours (kWh); the monthly figure multiplies that by the days used, the yearly one by 12 months, and each is priced at your tariff per kWh. A kWh is the "unit" counted on electricity bills.

People use it to compare appliances or to see what a heater or air conditioner adds to a bill. The default, a 1.5 kW heater running 4 hours a day for 30 days at 0.15 per kWh, uses 6 kWh a day and 180 kWh a month: 27.00 a month and 324.00 a year.

The rated wattage is a maximum. Fridges, air conditioners and heaters with thermostats cycle on and off, so their real use is lower, and tiered tariffs, standing charges and time-of-day rates change the final bill.

Exemples détaillés

1.5 kW heater, 4 h a day, 30 days at 0.15

Appliance power: 1500 W
Hours used per day: 4 h
Days used per month: 30 days
Price per kWh (unit): 0.15

Energy per day of use: 6 kWh
Energy per month: 180 kWh
Cost per month: 27.00
Cost per year: 324.00

Source de vérification : DOE method: 1500 W × 4 h ÷ 1000 = 6 kWh/day; × 30 × 0.15 = 27.00; × 12 = 324.00

100 W bulb, 5 h a day at 0.12

Appliance power: 100 W
Hours used per day: 5 h
Days used per month: 30 days
Price per kWh (unit): 0.12

Energy per month: 15 kWh
Cost per month: 1.80

Source de vérification : Python 3.8 decimal: 0.1 kW × 5 × 30 × 0.12

Two 1 hp motors, 8 h on 22 working days at 0.20

Appliance power: 1 hp
Hours used per day: 8 h
Days used per month: 22 days
Price per kWh (unit): 0.20
Number of appliances: 2

Energy per day of use: 11.9312 kWh
Cost per month: 52.50
Cost per year: 629.97

Source de vérification : Python 3.8 decimal: 2 × 745.69987 W × 8 h = 11.9312 kWh/day; × 22 × 0.20 = 52.4973

Ten 9 W LED bulbs, 6 h a day at ₹8

Appliance power: 9 W
Hours used per day: 6 h
Days used per month: 30 days
Price per kWh (unit): 8
Number of appliances: 10

Energy per month: 16.2 kWh
Cost per month: 129.60

Source de vérification : Python 3.8 decimal: 10 × 9 W × 6 h × 30 = 16.2 kWh; × 8 = 129.60

Questions

How do I calculate the cost of running an appliance?

Multiply the power in kilowatts by the hours of use to get kilowatt-hours, then multiply by the price per kWh. A 2,000 W (2 kW) heater used for 3 hours uses 6 kWh; at 0.15 per kWh that costs 0.90. The US Department of Energy gives the same method: watts × hours used per day ÷ 1,000 = daily kWh.

What is a unit of electricity?

One unit is one kilowatt-hour (kWh): 1,000 watts used for one hour, which is 3.6 megajoules of energy. A 100 W bulb takes 10 hours to use one unit and a 2 kW kettle takes 30 minutes. Bills in the UK, India and many other countries count units, and the price per unit is the tariff to enter here.

How do I find an appliance's wattage?

Look for the rating label on the back or base of the appliance, or in its manual; it lists watts or kilowatts. If it gives only amps, multiply by the supply voltage, as the US Department of Energy suggests: 5 A at 230 V is 1,150 W. A plug-in energy meter measures real consumption, including standby power and thermostat cycling.

How much electricity does a fridge use?

Less than its rating suggests, because the compressor switches on and off. The US Department of Energy suggests dividing the hours a fridge is plugged in by three to estimate its full-power running time, so a 150 W fridge runs about 8 hours a day: 1.2 kWh a day, or 36 kWh in a 30-day month. The kWh-per-year figure on its energy label is a better guide when you have it.

Quelle est la précision de « Electricity cost calculator » ?

La précision dépend de vos données et des hypothèses de la méthode. Le calcul décimal utilise 50 chiffres significatifs, mais les estimations, méthodes numériques et données sources peuvent être moins précises ; l’arrondi affiché ne supprime pas ces limites. Exemples résolus vérifiés à partir de sources indépendantes : 5. Par exemple, « 1.5 kW heater, 4 h a day, 30 days at 0.15 » est vérifié à l’aide de DOE method: 1500 W × 4 h ÷ 1000 = 6 kWh/day; × 30 × 0.15 = 27.00; × 12 = 324.00.

D’où vient cette méthode ?

U.S. Department of Energy — Estimating appliance and home electronic energy use; BIPM SI Brochure (9th ed.), Table 8 — the kilowatt-hour is 3.6 MJ.

À propos de ce calculateur

E_{\text{day}} = \frac{P \times h \times n}{1000}\ \text{kWh},\quad \text{cost}_{\text{month}} = E_{\text{day}} \times d \times \text{tariff},\quad \text{cost}_{\text{year}} = 12 \times \text{cost}_{\text{month}}

Sources

U.S. Department of Energy — Estimating appliance and home electronic energy use
BIPM SI Brochure (9th ed.), Table 8 — the kilowatt-hour is 3.6 MJ

Vérifié avec les références

Ce calculateur comprend 5 exemples résolus dont les réponses proviennent de sources indépendantes. Ils font partie de la suite de tests et peuvent aussi être exécutés ici.

Monthly cost with the same use (4 h a day, 30 days)

Power in kilowatts

Energy per day

Energy per month and year

Cost