Appliance running costs are one of the few household expenses where the math is completely transparent, and almost nobody does it. Every appliance sold in the US and EU carries a wattage rating. Multiply that by hours of use, divide by 1,000, multiply by your electricity rate, and you have the answer. The surprises are rarely where people expect them — the biggest single line item in most homes is not the refrigerator.
The formula
Monthly cost = (watts × hours per day × 30) ÷ 1000 × rate per kWh.
Working at the US average residential rate of 16.5 cents per kWh (EIA, 2026):
| Appliance | Typical draw | Hours/day | Monthly cost |
|---|---|---|---|
| Central AC (3-ton) | 3,500 W | 6 (seasonal avg) | $104 |
| Electric water heater | 4,000 W | 2.5 | $50 |
| Refrigerator | 150 W avg | 24 | $18 |
| Clothes dryer | 3,000 W | 0.8 | $12 |
| Dishwasher | 1,800 W | 0.7 | $6.20 |
| Space heater | 1,500 W | 4 (winter) | $30 |
| Desktop PC + monitor | 200 W | 8 | $7.90 |
| Clothes washer | 500 W | 0.6 | $1.50 |
| Microwave | 1,000 W | 0.15 | $0.74 |
| LED TV (55 inch) | 80 W | 5 | $1.98 |
Why heating and cooling dominate
Resistance heating converts electricity to heat at a 1:1 ratio, which is the worst efficiency in the house. A 1,500 W space heater running four hours a day costs as much as a refrigerator running around the clock, because the refrigerator only draws its full compressor load a fraction of the time. This is also why heat pumps beat resistance heaters by a factor of three to four — they move heat rather than generate it.
If you want the whole-house number rather than per-appliance math, our electricity cost calculator takes total usage and your rate, and the appliance energy use calculator handles the per-device breakdown.
A worked example: two identical houses
Take two 1,800 sq ft homes in the same city, both with two occupants and the same rate.
- House A: gas water heater, gas furnace, electric AC. Electric bill roughly $95/month.
- House B: electric resistance water heater, electric baseboard heat, electric AC. Electric bill roughly $280/month.
The appliances are the same. The difference is entirely in how the heating loads are powered. Nothing in House B involves a malfunction — it is all physics.
Phantom load is real but small
Devices on standby draw continuous low power. Across a typical home this totals 20-40 W, or about $2.50-5.00 per month. Charitably, that is 1-3% of a typical bill. It matters for the environment and it is worth handling, but it is not the lever most articles claim it is.
Frequently asked questions
Is it cheaper to run the dishwasher at night? Only if your utility has time-of-use rates. On a flat rate, no.
Does a full refrigerator cost more than an empty one? A full fridge costs less to run, because the stored mass holds temperature and the compressor cycles less. Air is a poor thermal buffer.
What is a kilowatt-hour worth where I live? US average is 16.5 cents, but state averages range from about 11 cents (Louisiana) to 40 cents (Hawaii). Always use your own rate from the bill.
Do smart plugs actually save money? They save the standby load of whatever is plugged into them, which is usually under $1 per month per device. They are useful for scheduling high-draw items, not for tiny standby savings.
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