The whole calculation
Electricity is billed in kilowatt-hours: one kilowatt drawn for one hour. Every appliance cost question is the same three-step arithmetic.
Cost = kWh × price per kWh
1,500 W × 8 h ÷ 1,000 = 12 kWh
12 kWh × $0.17 = $2.04 per day
The only genuinely fiddly part is the hours. A refrigerator is plugged in 24 hours a day but its compressor cycles, so it draws its rated wattage only part of the time. Wattage on a nameplate is peak draw, not average.
Monthly cost by appliance
At $0.17 per kWh, a mid-range US residential rate:
| Appliance | Watts | Hours/day | kWh/day | Cost/month |
|---|---|---|---|---|
| Central air conditioning | 3500 W | 6 h | 21.00 | $107.10 |
| Electric space heater | 1500 W | 8 h | 12.00 | $61.20 |
| Clothes dryer | 3000 W | 1 h | 3.00 | $15.30 |
| Electric oven | 2400 W | 1 h | 2.40 | $12.24 |
| Water heater (electric) | 4000 W | 3 h | 12.00 | $61.20 |
| Dishwasher | 1800 W | 1 h | 1.80 | $9.18 |
| Desktop PC + monitor | 200 W | 8 h | 1.60 | $8.16 |
| Refrigerator | 150 W | 24 h | 3.60 | $18.36 |
| LED TV, 55 inch | 90 W | 5 h | 0.45 | $2.30 |
| Ceiling fan | 60 W | 8 h | 0.48 | $2.45 |
| LED bulb | 10 W | 6 h | 0.06 | $0.31 |
| Wi-Fi router | 10 W | 24 h | 0.24 | $1.22 |
The pattern is consistent: anything that makes heat or moves heat dominates the bill. Air conditioning, electric heating, water heating and clothes drying sit at the top. Electronics that people worry about — routers, TVs, standby draw — are pennies by comparison.
What your rate does to the answer
US residential rates range from roughly 11 cents per kWh to over 40 cents depending on state and plan. Monthly cost for three appliances across that range:
| Rate | Space heater | Central AC | Refrigerator |
|---|---|---|---|
| $0.12/kWh | $43.20 | $75.60 | $12.96 |
| $0.15/kWh | $54.00 | $94.50 | $16.20 |
| $0.17/kWh | $61.20 | $107.10 | $18.36 |
| $0.22/kWh | $79.20 | $138.60 | $23.76 |
| $0.30/kWh | $108.00 | $189.00 | $32.40 |
Your actual rate is on your bill, though the headline figure often excludes delivery charges, which can be a third or more of the total. Dividing your total bill by total kWh used gives the effective rate that matters.
Where the savings actually are
- Thermostat setpoints. Each degree of heating or cooling setback is typically worth a few percent on that load — and heating and cooling are usually the largest line on the bill.
- Water heater temperature. Dropping from 60°C to 49°C (140°F to 120°F) reduces standby losses noticeably and is generally recommended anyway.
- Line drying. A dryer at 3,000 W is one of the most expensive things in the house per hour of use.
- Old refrigerators. A second fridge in a garage from twenty years ago can cost several times what a modern one does.
Standby power is real but small — typically 5 to 10% of a household bill spread across many devices. It is worth addressing, but not before the heating and cooling loads.
Measuring rather than estimating
A plug-in energy monitor costs very little and removes the guesswork entirely, recording actual kWh over days or weeks. For anything that cycles — fridges, freezers, pumps, air conditioning — measured consumption is far more accurate than nameplate wattage multiplied by hours.
Run any appliance through the electricity cost calculator, size a whole-house load with the wattage calculator, or check what that consumption means in solar panels.
Run your own numbers
FAQ
How do I calculate the cost of running an appliance?
What uses the most electricity in a house?
How much does it cost to run a space heater?
Is standby power worth worrying about?
Why does my fridge cost less than its wattage suggests?
Sources
Primary references used for the figures and rules on this page.
- Electric Power Monthly — average retail price of electricity — U.S. Energy Information Administration
- Energy Efficient Products — ENERGY STAR