Electricity Cost Calculator
With power 1500 W, hours used a day 4, days used a year 120, your electricity rate 17.5 cents per kWh and 1 more field, electricity cost comes to $126.00 — cost a year. It is reached in 10 steps, the last of which is 720 * 17.5 / 100, and each one is printed on the page with its numbers filled in. The formula is the one published by US Energy Information Administration, not an approximation fitted to it.
What an appliance costs to run by the hour, day, month and year, from its wattage and your tariff.
Formula and sources checked · How we check
Power 1500 W, Hours used a day 4, Days used a year 120, Your electricity rate 17.5 cents per kWh
$126.00
Cost a year for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Kilowatt-hours an hour
1500 / 10001.5 kWh- Cost an hour
1.5 * 17.5 / 100$0.26- Kilowatt-hours a year in use
1.5 * 4 * 120720 kWh- Hours a year on standby
max(0, 8760 - 4 * 120)8,280 hours- Kilowatt-hours a year on standby
0 / 1000 * 82800 kWh- Kilowatt-hours a year in total
720 + 0720 kWh- Cost a day in use
0.2625 * 4$1.05- Cost a month
720 * 17.5 / 100 / 12$10.50- Cost a year
720 * 17.5 / 100$126- Of which standby
0 * 17.5 / 100$0
Worked example
A 1,500 W space heater run four hours a day through a 120-day winter uses 720 kWh and costs $126 a year. Per hour it is 26 cents — which is why heating one room with electricity is cheap and heating a house with it is not.
How to work it out yourself
- 1.Take the wattage from the appliance label or its manual. Where only amps are given, multiply by the voltage: 12.5 A at 120 V is 1,500 W.
- 2.Work out your real rate from a bill: divide the total charge by the kilowatt-hours used. The headline supply rate leaves out delivery charges, which are often a third of the bill.
- 3.Add the standby figure for anything that is never truly off. It runs for the 8,000-odd hours a year the appliance is idle, which is where it stops being trivial.
What a year costs, by wattage
| Power (W) | Cost a year | Kilowatt-hours a year in total | Cost a month |
|---|---|---|---|
| 5 | $0.42 | 2.4 kWh | $0 |
| 10 | $0.84 | 4.8 kWh | $0 |
| 50 | $4.20 | 24 kWh | $0 |
| 100 | $8.40 | 48 kWh | $1 |
| 200 | $16.80 | 96 kWh | $1 |
| 500 | $42.00 | 240 kWh | $4 |
| 800 | $67.20 | 384 kWh | $6 |
| 1000 | $84.00 | 480 kWh | $7 |
| 1500 | $126.00 | 720 kWh | $11 |
| 2000 | $168.00 | 960 kWh | $14 |
| 3000 | $252.00 | 1,440 kWh | $21 |
Four hours a day for 120 days at 17.5 cents a kilowatt-hour.
The formula
- Kilowatt-hours an hour
1500 / 1000 - Cost an hour
1.5 * 17.5 / 100 - Kilowatt-hours a year in use
1.5 * 4 * 120 - Hours a year on standby
max(0, 8760 - 4 * 120) - Kilowatt-hours a year on standby
0 / 1000 * 8280 - Kilowatt-hours a year in total
720 + 0 - Cost a day in use
0.2625 * 4 - Cost a month
720 * 17.5 / 100 / 12 - Cost a year
720 * 17.5 / 100 - Of which standby
0 * 17.5 / 100
Source: US Energy Information Administration — average price of electricity to ultimate customers, NIST Special Publication 811 — Guide for the Use of the International System of Units
Questions people actually ask
- How do I find my real electricity rate?
- Divide the total on the bill by the kilowatt-hours it covers. The number advertised by a supplier is usually the energy charge alone, and delivery, transmission and fixed charges can add half again. The all-in figure is the only one that answers "what does this appliance cost me".
- Does standby power really matter?
- It adds up because it never stops. A device drawing 5 W constantly uses 44 kWh a year — about $7.70 at 17.5 cents — and a household with thirty such devices is paying a couple of hundred dollars a year for things that are switched off. The individual figures are trivial and the total is not.
- Why is my heater so expensive to run?
- Because resistance heating converts electricity to heat one to one, and electricity costs three to four times as much per unit of energy as gas. A 1,500 W heater is the largest load most sockets will carry, and running two of them costs more per hour than almost anything else in the house. A heat pump moves two to four times as much heat per unit of electricity, which is the whole argument for one.
- What uses the most electricity in a house?
- Heating and cooling, usually by a wide margin, then water heating, then the fridge — which is modest per hour and runs all year. Lighting has fallen to a small share since LEDs, and the devices people worry about most, chargers and televisions, are rarely near the top.
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