Electricity Cost Calculator
Work out what an appliance costs to run per hour, day, month, and year from its wattage, usage hours, and your electricity rate per kWh.
Como usar esta calculadora
- 1Find the appliance's wattage — it is on the label, the nameplate, or the manual.
- 2Enter how many hours a day and days a week it actually runs.
- 3Enter your electricity rate per kWh from your bill, not the headline advertised rate.
- 4Compare the annual figure against the cost of a more efficient replacement.
Como funciona
Electricity cost formula
kW = watts ÷ 1000 kWh per day = kW × hours used per day kWh per year = kWh per day × (days per week ÷ 7) × 365.25 cost = kWh × rate per kWh
A kilowatt-hour is the energy used by a one-kilowatt load running for one hour, and it is the unit every electricity bill is priced in. The whole calculation is therefore power converted to kilowatts, multiplied by hours, multiplied by the rate. A 1,500 W heater is 1.5 kW, so four hours costs 6 kWh — no matter how that time is spread out.
Exemplo resolvido
A 1,500 W space heater run four hours a day, every day, at $0.17 per kWh: 1.5 kW × 4 h = 6 kWh a day, or about 2,192 kWh a year, costing roughly $373.
Electricity Cost Calculator: o guia completo
Finding your real rate per kWh
The most reliable method is arithmetic rather than reading the tariff: take your total bill, subtract any fixed standing charge, and divide by the kilowatt-hours used. That gives the marginal rate — what one extra unit actually costs you, which is the number that matters when deciding whether to run something.
Tariffs complicate this. Tiered pricing raises the rate above a monthly threshold, so extra consumption may cost considerably more than your average rate suggests. Time-of-use pricing charges more during peak hours, which is why running a dishwasher overnight can genuinely be cheaper than running it at 6 pm.
What actually costs money in a house
Heating and cooling dominate almost every bill, typically around half of total usage. Water heating is usually next, then refrigeration, then laundry. Electronics and lighting are far smaller than most people assume, particularly since LED lighting became standard.
The pattern is that heat is expensive. Anything that turns electricity into heat — space heaters, kettles, ovens, tumble dryers, hair dryers — draws over a kilowatt and adds up fast. Anything that processes information draws a few watts and does not.
A useful heuristic: a 1,000 W appliance running one hour a day costs about $62 a year at $0.17 per kWh. Scale from there.
Standby power
Devices left plugged in draw power even when off — set-top boxes, game consoles in instant-on mode, older TVs, and anything with a power brick. Individually it is 1 to 10 watts; across a whole house it commonly totals 50 to 100 watts running continuously.
Enter 50 W for 24 hours a day above and the annual cost lands around $75. That is the value of a few smart plugs or switched power strips on the entertainment centre, and it is one of the rare energy savings that requires no behaviour change at all.
Working out whether an upgrade pays back
Run this calculator twice — once with the old appliance's wattage and once with the new one's — and take the difference in annual cost. Divide the purchase price by that saving to get the payback period in years.
Replacing a 100 W incandescent bulb with a 10 W LED running five hours a day saves about $28 a year, so a $5 bulb pays back in ten weeks. Replacing a working refrigerator to save 200 kWh a year saves about $34, so a $900 appliance takes over twenty-five years — the upgrade only makes sense when the old one fails anyway.
Perguntas frequentes
How much does it cost to run a 1500W heater?
About $0.26 an hour at $0.17 per kWh. Running four hours a day costs roughly $31 a month, or $372 a year. Space heaters are among the most expensive appliances in a home precisely because they convert electricity directly into heat at full power.
What is a kWh?
A kilowatt-hour is the energy consumed by a 1,000 W load running for one hour. It is the billing unit on every electricity statement — sometimes called a "unit" — so a 2,000 W appliance running 30 minutes uses exactly 1 kWh.
Where do I find an appliance's wattage?
On the nameplate label, usually on the back or underside, or in the manual. If only volts and amps are given, multiply them: 120 V × 12 A is 1,440 W. A plug-in energy monitor is the most accurate option, since many appliances cycle rather than drawing their rated power continuously.
Does turning appliances off at the wall actually save money?
Yes, though the amount depends on the device. Anything with a remote, a clock, a network connection, or an external power brick draws standby power continuously. Across a household it typically totals 50–100 W, which is $75–$150 a year at average US rates.