This electricity cost calculator answers the question behind many a household argument: what does that appliance actually cost to run? Enter wattage, daily hours and your electricity rate for day, month and year costs.
Find your rate on your bill: total $ ÷ total kWh gives your true all-in rate (the printed energy charge often excludes delivery and fees — the all-in figure is usually 30–60% higher).
The One Formula Behind Every Electric Bill
kWh = watts × hours ÷ 1000, then multiply by your rate. A kilowatt-hour is simply 1,000 watts running for one hour — the unit your meter counts and your bill prices. Everything else on this page is that formula wearing calendar clothes. This calculator is part of our Everyday Life Calculators collection.
Worked Example (Verified)
A 1,500 W space heater, 5 hours a day, at a typical all-in rate of $0.17/kWh:
- Energy: 1.5 kW × 5 h = 7.5 kWh/day
- Cost: 7.5 × $0.17 = $1.28/day → $38.25/month → $466/year if run daily year-round
- The seasonal reality: run it only on 90 winter days and the bill is ~$115 — which is why the “year” card needs your judgment about seasons
Typical Wattages (for Your Next Argument)
| Appliance | Watts | At 5 h/day, per month* |
|---|---|---|
| LED bulb | 9 W | $0.23 |
| Laptop | 50 W | $1.28 |
| Television (55″) | 100 W | $2.55 |
| Gaming PC under load | 400 W | $10.20 |
| Microwave | 1,200 W | (but minutes/day, not hours) |
| Space heater / hair dryer | 1,500 W | $38.25 |
| Window air conditioner | 1,000–1,500 W | $25–38 |
*At $0.17/kWh. The pattern to notice: heating and cooling dominate — anything that makes heat or cold is a kilowatt-class device, while lights and electronics are rounding errors by comparison. A refrigerator (~150 W cycling, effectively ~8–12 h/day of runtime) typically lands at $8–15/month.
Finding Your Wattage and Rate
- Wattage is printed on the appliance label or power brick (or search the model + “watts”). Use the maximum for heaters; electronics draw far less than their adapter’s rating in normal use.
- Standby (“vampire”) loads of 5–10 W per device cost roughly $8–15 per device per year at 24/7 — small numbers, many devices.
- Time-of-use plans price evening kWh higher; if your plan has peak/off-peak rates, run the calculator at both rates before deciding when to run big loads.
Related Tools
- Everyday Life Calculators — the full collection
- MPG Calculator — the fuel-side twin
Frequently Asked Questions
How do I calculate the cost of running an appliance?
kWh per day = watts ÷ 1000 × hours per day; cost = kWh × your rate. A 1,500 W heater at 5 h/day uses 7.5 kWh — at $0.17/kWh that is $1.28 a day.
What is a kilowatt-hour?
The energy of running 1,000 watts for one hour. Your bill counts and prices these; the average US home uses roughly 30 kWh per day.
What is the average electricity rate in the US?
About $0.17/kWh all-in nationally, ranging from ~$0.11 in the cheapest states to over $0.30 in Hawaii, California and parts of New England. Use your own bill’s total ÷ kWh for accuracy.
How much does it cost to leave a light on all day?
A 9 W LED for 24 hours uses 0.216 kWh — about 4 cents a day. The old 60 W incandescent was 24 cents a day; the LED switch quietly pays for itself in weeks.
Why is my bill higher than the sum of my appliances?
Fixed customer charges, delivery fees and taxes sit on top of energy; plus the big intermittent loads (water heater, HVAC, dryer, oven) are easy to underestimate. The all-in rate method in the note under the calculator absorbs the fees fairly.
Is this electricity cost calculator free?
Yes — free, instant, no sign-up.