Electricity Cost Calculator
What an appliance costs to run, from the electricity cost calculator, and which appliances are worth the attention. It is almost never the ones people switch off.
Cost per year
- Cost per year 1,080 kWh at 17.5 cents.
- $189.00
- Cost per hour 1.5 kWh an hour.
- $0.26
- Cost per day 6 hours of use.
- $1.58
- Cost per month Averaged over the year. A seasonal appliance costs nothing for most of it and far more than this in its months.
- $15.75
- The arithmetic A kilowatt-hour is one kilowatt drawn for one hour. Watts are a rate; kilowatt-hours are a quantity, and the bill charges for the quantity.
- 1500 W / 1000 x 6 h = 9 kWh a day
- In context The average US household uses about 10,500 kWh a year. Anything under about 1% of that is not where a bill is won or lost.
- 10.3% of an average US home's use
- What dominates a bill Anything that makes heat is in the kilowatts; anything that processes information is in the watts. A space heater at 1,500 W uses as much in one hour as a 9 W LED bulb does in a week. Turning off a phone charger is not a strategy.
- heating, cooling, water heating
| Appliance | Watts | Hours/day | Cost a year |
|---|---|---|---|
| Space heater | 1500 | 6 | $574.88 |
| Window air conditioner | 1200 | 8 | $613.20 |
| Electric oven | 2400 | 1 | $153.30 |
| Clothes dryer | 3000 | 1 | $191.63 |
| Dishwasher | 1800 | 1 | $114.98 |
| Desktop PC and monitor | 200 | 8 | $102.20 |
| Refrigerator (averaged) | 150 | 24 | $229.95 |
| LED bulb | 9 | 5 | $2.87 |
| Incandescent bulb | 60 | 5 | $19.16 |
| TV (55 inch LED) | 85 | 5 | $27.15 |
- Nameplate wattage is the maximum draw, not the average. Anything with a thermostat or a compressor (a fridge, an air conditioner, a heat pump) cycles on and off, so its real consumption is well below its rating times hours.
- Rates vary enormously by location and often by time of day. A time-of-use tariff can make the same kilowatt-hour cost three times more at 6pm than at 2am, which changes the answer for anything schedulable.
How the Electricity Cost Calculator works
Electricity is billed by the kilowatt-hour, and the whole calculation is turning a wattage into kilowatt-hours and multiplying by a rate.
A watt is a rate of energy use. A kilowatt-hour is a quantity: one kilowatt drawn for one hour. So divide the wattage by 1,000 and multiply by the hours. A 1,500 W space heater running six hours uses 9 kWh, and at 17.5 cents that is $1.58 a day. Over a 120-day winter it is $189.
The distinction between watts and kilowatt-hours is where most confusion lives. Watts tell you how fast a device consumes; kilowatt-hours tell you how much it consumed. A 3,000 W clothes dryer draws twice as fast as a 1,500 W heater and costs less to run over a day, because it runs for one hour and the heater runs for six.
That leads to a rough division of appliances into two classes.
Things that make heat or move it are measured in kilowatts. Space heaters, electric ovens, clothes dryers, kettles, water heaters, air conditioning. These are 1,000 to 4,000 W and they dominate a bill. Heating, cooling and water heating together are typically well over half of residential electricity use.
Things that process information are measured in watts. LED bulbs at 9 W, a TV at 85 W, a laptop at 50 W, a phone charger at 5 W. These are two to three orders of magnitude smaller. A 1,500 W heater uses as much in a single hour as a 9 W LED bulb does in a week.
The practical consequence is that almost all popular energy-saving advice is aimed at the wrong category. Unplugging a phone charger saves perhaps 50 cents a year. Lowering a thermostat by one degree saves 1 to 3% of heating cost, which on a $1,200 annual heating bill is $12 to $36 for a change you may not notice. The attention is better spent on the kilowatt items.
Standby power is the partial exception. No single device matters much, but there are so many of them. A television, a game console, a set-top box, a microwave with a clock, and a dozen chargers each drawing 1 to 3 watts around the clock add up to roughly 5 to 10% of a residential bill. The devices worth targeting are the ones that draw real standby power: older set-top boxes and game consoles can draw 15 to 20 W while apparently off.
Two caveats on the arithmetic. Nameplate wattage is the maximum, not the average, and anything with a thermostat or a compressor cycles. A fridge rated 150 W does not draw 150 W for 24 hours; it runs perhaps a third of the time, which is why its yearly figure on an energy label is far below the naive calculation. For those, the kWh-per-year figure on the label beats any multiplication.
And rates are not a single number. US residential rates range from about 11 cents in Louisiana to over 40 in Hawaii, and many utilities now offer time-of-use tariffs where the same kilowatt-hour costs three times more at 6pm than at 2am. For anything schedulable (a dishwasher, a dryer, an EV charger), the time of day can matter more than the appliance's efficiency.
Electricity Cost Calculator FAQ
How do I work out what an appliance costs to run?
Divide the wattage by 1,000 to get kilowatts, multiply by the hours used, then multiply by your rate per kWh. A 1,500 W heater for 6 hours is 9 kWh, and at 17.5 cents that is $1.58 a day. The wattage is on the label or the nameplate.
What is the difference between a watt and a kilowatt-hour?
A watt is a rate of use and a kilowatt-hour is a quantity used. A 1,000 W device running for one hour consumes 1 kWh. Your bill charges for the quantity, which is why a high-wattage device used briefly can cost less than a low-wattage one left on.
Does unplugging things actually save money?
A little. Standby draw is typically 1 to 3 watts per device, which is around 50 cents to $4 a year each, and across a whole house it comes to 5 to 10% of a bill. The devices worth unplugging are older set-top boxes and game consoles, which can draw 15 to 20 W while apparently off.
What uses the most electricity in a house?
Anything that makes or moves heat: space heating, air conditioning, water heating, electric ovens and clothes dryers. These run at 1,000 to 4,000 watts and together are usually well over half a residential bill. Electronics and lighting are two to three orders of magnitude smaller.