Electricity Cost Calculator
What an appliance costs to run, per day, week, month and year. Give it the wattage, the hours it actually draws power, and the price you pay for a kilowatt-hour.
What it draws, and for how long
Fills in a typical draw and run time. Every figure is a starting point, not your appliance.
The rated draw from the label or the spec sheet. This is what it pulls while running, not an average over the day.
Labels state watts; heat pumps and ovens are sometimes quoted in kilowatts. 1 kW is 1,000 W.
Hours it is actually drawing power — not hours plugged in. A fridge is on all day and runs for about eight of them.
Seven for anything left running. Fractions work: every other day is 3.5.
Your bill total divided by the units it charged for — that blend includes standing charges and beats the headline rate.
0.15 kW for 8 hours a day, 7 days a week, is 1.2 kWh a day and 438 kWh a year.
- Power draw
- 0.15 kW
- Energy per day
- 1.2 kWh
- Energy per year
- 438 kWh
- Cost per day
- $0.204
- Cost per month
- $6.21
- Cost per year
- $74.46
| Period | Energy | Cost |
|---|---|---|
| Day | 1.2 kWh | $0.204 |
| Week | 8.4 kWh | $1.43 |
| Month | 36.5 kWh | $6.21 |
| Year | 438 kWh | $74.46 |
- A refrigerator (running) is governed by a thermostat, so it is powered far longer than it draws power. The hours above are running hours; multiplying the nameplate by 24 would overstate this by roughly threefold.
- A plug-in energy monitor settles it. It reads real kilowatt-hours over a week and removes every guess on this page except the price.
- Standby draw is not included. A device that is “off” may still pull 1–5 W, which is pennies alone and a real line on the bill across a house full of them.
- A year is 365 days and a month is a twelfth of one, so the twelve monthly figures add up to the annual figure.
Watts to kilowatt-hours to money, in three steps
Your bill charges for energy, not power. Power is how hard the appliance pulls; energy is how long it pulls for. The whole calculation is turning one into the other.
kWh/day = (W ÷ 1000) × h • kWh/year = kWh/day × d × (365 ÷ 7) • cost = kWh × price- W
- The appliance’s draw in watts, while running
- h
- Hours a day it actually draws power
- d
- Days a week it is used
- price
- Your blended cost of one kilowatt-hour
Two conventions worth stating, because calculators differ on both. A year here is 365 days, not 52 weeks — 52 weeks is 364 days and quietly loses a quarter of a percent. And a month is a twelfth of a year rather than 30 days, so the twelve monthly figures add up to the annual one; twelve 30-day months would only be 360 days.
A 150 W refrigerator, done twice
A fridge with a 150 W compressor, running about eight hours out of every twenty-four, seven days a week, at 17¢ per kilowatt-hour. 150 ÷ 1000 = 0.15 kW. 0.15 × 8 = 1.2 kWh a day. Over 365 days that is 438 kWh, and at $0.17 the year costs $74.46 — about $6.21 a month, or 20.4¢ a day.
Now do it the way most people do, with 24 hours instead of 8. 0.15 × 24 = 3.6 kWh a day, 1,314 kWh a year, $223.38. Same appliance, same tariff, same formula — and an answer three times too big, because the input was hours plugged in rather than hours drawing power.
A nameplate is a running figure, and a fridge does not run
Anything with a thermostat spends most of its life waiting. A refrigerator cools until the cabinet reaches its set point, stops, and does nothing until the temperature drifts back up. That on-fraction — the duty cycle — is typically somewhere around a third for a modern fridge in a normal kitchen, and it moves with the room temperature, how full the fridge is, how often the door opens and how good the door seal still is.
The same is true of a freezer, a window or central air conditioner, a space heater, an electric water heater and an electric oven once it is up to temperature. For all of them, the nameplate wattage is correct and multiplying it by the hours the thing is switched on is wrong. Use running hours instead, and treat any figure you have not measured as a guess with a wide range around it.
The way to stop guessing is to measure. A plug-in energy monitor costs about the same as a month of running the appliance, sits between the plug and the socket, and reports actual kilowatt-hours over however long you leave it there. A week is enough for anything that cycles. That reading removes every assumption on this page except the price.
Typical wattages, and what a year of each costs
Costed at $0.17 per kilowatt-hour, seven days a week. The four thermostatic entries — refrigerator, window air conditioner, space heater and central air conditioning — are listed with running hours, which is why the fridge shows eight rather than twenty-four. Every figure is a round number on purpose: real draw varies by model, age and setting far more than a third significant figure would suggest.
| Appliance | Typical draw | Hours a day drawing power | Cost a year |
|---|---|---|---|
| LED bulb | 10 W | 5 | $3.10 |
| Laptop | 50 W | 6 | $18.62 |
| TV (55-inch LED) | 100 W | 4 | $24.82 |
| Refrigerator (running) — cycles | 150 W | 8 | $74.46 |
| Desktop PC | 200 W | 6 | $74.46 |
| Washing machine | 500 W | 1 | $31.03 |
| Window air conditioner — cycles | 900 W | 8 | $446.76 |
| Microwave | 1000 W | 0.25 | $15.51 |
| Electric kettle | 1500 W | 0.25 | $23.27 |
| Hair dryer | 1500 W | 0.25 | $23.27 |
| Space heater — cycles | 1500 W | 6 | $558.45 |
| Dishwasher | 1800 W | 1 | $111.69 |
| Electric oven | 2400 W | 1 | $148.92 |
| Tumble dryer | 3000 W | 1 | $186.15 |
| Central air conditioning — cycles | 3500 W | 8 | $1,737.40 |
The ordering is by wattage, and it is not the ordering of the costs. An electric kettle draws ten times what a refrigerator does and costs under a third as much across a year, because it runs for fifteen minutes rather than eight hours. The 150 W fridge and the 200 W desktop land on the same $74.46 from entirely different directions. Wattage tells you what the circuit has to carry; wattage multiplied by hours tells you what the bill will be.
One caveat on the seasonal rows. The heaters and air conditioners are costed at seven days a week for a full year, which nobody does — a space heater run for three winter months costs a quarter of the $558 shown. Scale those rows by the fraction of the year you actually run them, or set the days per week in the calculator to the seasonal average.
The watts you pay for while nothing is on
A device that is “off” is usually only mostly off. Anything with a remote receiver, a clock, a network connection or a mains adapter keeps drawing something — commonly 1 to 5 W, which is 9 to 44 kWh a year each. One of them is not worth a thought. A house with a dozen is paying for something in the region of 300 kWh a year, more than the refrigerator in the example above, for nothing at all.
This calculator does not include standby draw, because folding a guess into an appliance figure hides it. Run it as its own sum instead: enter the standby wattage, 24 hours a day, seven days a week, and see what that device costs you to leave plugged in.
Sizing the unit, then running it
- BTU calculator — for choosing the air conditioner or heater in the first place. Watch the units when you move between the two pages: a BTU rating is heat moved, not power drawn. An air conditioner rated at 12,000 BTU/h does not draw 12,000 W — it moves several times more heat than the electricity it consumes, which is the whole point of a heat pump. Take the electrical input in watts off the spec sheet and bring that number here.
What this calculator assumes
- The appliance draws its stated wattage for exactly the hours you give it, and nothing at all for the rest of the day. Real appliances ramp, cycle and idle; this is a rectangle drawn over a jagged shape.
- One flat price per kilowatt-hour. Time-of-use bands, tiered rates, demand charges and seasonal pricing are all real and all specific to one supplier — use your blended rate, bill total divided by units.
- A year is 365 days. A leap year adds a day, which is 0.3% on the annual figure and less than the error in the wattage.
- Standby draw is excluded. So is the heat an appliance dumps into a room your air conditioner then has to remove, which is a real second-order cost in summer and a small saving in winter.
- No currency conversion. The answer comes back in whatever currency you priced the kilowatt-hour in.
Electricity cost FAQ
How much does it cost to run a refrigerator for a year?
For a typical 150 W fridge running about eight effective hours a day at 17¢ per kilowatt-hour, roughly $74 a year. The number people usually quote is three times that, because they multiply 150 W by 24 hours — a fridge is powered around the clock but its compressor only runs for a fraction of it.
Do I use the wattage printed on the appliance?
Yes, but understand what it means. The nameplate figure is the draw while the appliance is running at full tilt, not an average over the day. For anything a user switches on and off — a kettle, a TV, a hair dryer — that is exactly right, and you just need the hours. For anything a thermostat governs, the nameplate is right and the hours are the problem: enter running hours, not plugged-in hours.
What is a kilowatt-hour?
One kilowatt of draw for one hour. A 1,000 W appliance uses one kilowatt-hour per hour; a 100 W one takes ten hours to use the same. It is the unit your bill charges in, which is why every calculation here converts to it first.
How do I find my real price per kilowatt-hour?
Take your bill total — including standing charges, taxes and any fixed fees — and divide it by the kilowatt-hours the bill says you used. That blended figure is what an extra unit actually costs you, and it is usually a couple of cents above the headline rate on the tariff sheet.
My appliance is rated in amps, not watts. What do I do?
Multiply amps by volts. A 12.5 A appliance on a 120 V circuit is 1,500 W; the same rating on a 230 V supply is 2,875 W. Nameplate amp ratings are usually the maximum the appliance can draw rather than what it draws in normal use, so treat the result as an upper bound.
Is standby power worth worrying about?
Per device, no — a set-top box pulling 3 W costs about $4.50 a year. Across a house, it adds up: a dozen devices averaging 3 W each is over 300 kWh a year, which is more than the fridge on this page. Smart speakers, games consoles in rest mode, and anything with a mains adapter are the usual offenders.
Sources and review notes
- US Energy Information Administration — Electricity, for the average residential price per kilowatt-hour by state and month
- Lawrence Berkeley National Laboratory — Standby Power, for measured standby draw across device categories
The 17¢ default is a round figure near the recent US residential average; the EIA page above carries the current number, and it varies by more than a factor of two between states. Nothing else on this page depends on it — put your own rate in and every figure moves with it.