Calculators
Electricity Cost Calculator
Add your appliances, their wattage and how long they run, then enter your price per kWh to see what each one and the whole list costs per day, month and year.
Use the energy (per kWh) rate from your bill. Fixed daily or monthly charges are not included.
DOE nameplate range: 120 W
0.480 kWh/day · 175.2 kWh/year · 29.78 per year
DOE nameplate range: 50 W
0.300 kWh/day · 109.5 kWh/year · 18.62 per year
DOE nameplate range: 1500 W (DOE worked example)
0.375 kWh/day · 136.9 kWh/year · 23.27 per year
5.97
per month (average)
35.1
kWh per month
| Energy | Cost | |
|---|---|---|
| Per day | 1.16 kWh | 0.20 |
| Per month | 35.13 kWh | 5.97 |
| Per year | 421.58 kWh | 71.67 |
How it is calculated and tips
- kWh per day = watts × hours ÷ 1000, plus standby watts × the remaining hours. Days per week spreads the use over the year; a year is 365 days and a month is a year ÷ 12.
- The wattage on the label is the maximum draw. Appliances with settings or thermostats (heaters, fridges, air conditioners) often use less on average.
- A plug-in electricity usage monitor measures the real draw and kWh of a 120 V or 230 V plug-in device over days, which is the most accurate input for cycling appliances.
- If a label lists amps instead of watts, multiply amps by the supply voltage to estimate watts.
Estimates from the figures you enter. Processed on your device — nothing is sent anywhere.
Works in your browser. No account needed.
Frequently asked questions
How do I calculate the electricity cost of an appliance?
Multiply the wattage by the hours used per day and divide by 1,000 to get kWh per day. Multiply by the number of days it is used in a year for annual kWh, then by your price per kWh for the annual cost. This is the method the U.S. Department of Energy gives: a 1,500 W kettle used 1 hour a day uses 1.5 kWh a day, or 547.5 kWh a year, which costs 60.23 at 0.11 per kWh.
What is a kilowatt-hour?
A kilowatt-hour (kWh) is the energy used by a 1,000 W load running for one hour, or a 100 W load running for ten hours. Electricity bills charge by the kWh, so converting each appliance’s watts and hours into kWh is what lets you put a price on it.
Where do the preset wattages come from?
They come from the U.S. Department of Energy’s Energy Saver list of typical nameplate wattages for household appliances, and the range is shown under each appliance. Nameplate wattage is the maximum an appliance can draw, and some entries in that list date from older equipment, so a modern TV or monitor often uses much less. The figure on your own appliance’s label, or a measurement, is always better.
What is standby power and should I include it?
Many devices keep drawing a small amount of power when switched off but still plugged in, such as televisions, stereos, computers and kitchen appliances; the DOE calls these phantom loads. Enter the standby watts if you know them, and the calculator adds them for every hour the appliance is not in use. Unplugging, or using a power strip with a switch, removes them.
Why is my bill different from the estimate?
Appliances with thermostats or settings, like fridges, heaters and air conditioners, cycle on and off, so they rarely draw their full rating all the time; the DOE suggests treating a fridge as running for a third of the time it is plugged in. Bills also include fixed charges, taxes and, in some places, time-of-use or tiered rates that this calculator does not model.
How can I measure an appliance’s real power use?
Plug it into an electricity usage monitor, a small meter that sits between the socket and the appliance and shows watts and cumulative kWh. Leaving it connected for a few days gives a realistic average for appliances that cycle. For appliances you cannot plug into a monitor, use the nameplate or the manufacturer’s specification; many major appliances also carry an EnergyGuide or energy label stating estimated yearly energy use.
About this tool
This electricity cost calculator estimates how much energy your appliances use and what it costs. Build a list of appliances, give each one a wattage, hours of use per day, days per week, standby wattage and quantity, and enter the price you pay per kWh. The calculator shows kWh and cost for each appliance and a total per day, per month and per year, and it works with any currency because you type in your own rate.
The math follows the method on the U.S. Department of Energy’s Energy Saver page on estimating appliance energy use: watts × hours per day ÷ 1,000 gives kWh per day, multiplying by days of use gives kWh per year, and multiplying by the rate gives the cost. Standby power is added for the rest of each day, including days the appliance is not used. A year is 365 days and a month is one twelfth of a year, so monthly figures are averages rather than a particular calendar month.
The presets use the DOE’s published nameplate wattages, from a coffee maker at 900–1,200 W to a 40-gallon water heater at 4,500–5,500 W, and the default hours are only examples. Nameplate wattage is the maximum draw, and several entries in the DOE list reflect older equipment, so replace the figures with the wattage on your own appliance, its EnergyGuide label, or a reading from a plug-in usage monitor wherever you can. For a fridge, which cycles on and off, the DOE suggests counting a third of the time it is plugged in, and the same reasoning applies to other thermostat-controlled appliances.
Common uses are finding which appliances dominate a bill, pricing a space heater or dehumidifier before buying, checking how much standby devices cost over a year, and comparing an old appliance with a more efficient replacement. The result is an estimate: fixed charges, taxes, tiered and time-of-use tariffs are not included. Everything runs in your browser and nothing you enter is sent anywhere.