That space heater feels cheap until the bill arrives. Every appliance’s cost comes down to three numbers — its wattage, how long it runs, and what your utility charges per kilowatt-hour — and most people never do the math until the statement shocks them.
Want to track usage in kWh? Try our Electricity Usage Calculator.
This free electricity cost calculator does it in seconds: pick an appliance preset (or enter custom wattage), add daily hours and your rate, and get daily, monthly and yearly kWh and cost, plus an estimated CO₂ footprint. All calculations happen privately in your browser.
Appliance energy · kWh & cost per day / month / year
Please enter a wattage above zero, hours between 0 and 24, and a valid rate.
Estimates only — actual bills vary with tiered rates, fees and taxes. CO₂ uses the US grid average of ~0.85 lbs per kWh. Check your utility bill for your exact per-kWh rate.
How to Use This Calculator
- Pick an appliance preset — space heater, AC, fridge, oven and more auto-fill typical wattage; or choose Custom and type your own.
- Enter daily hours of use and days per month the appliance runs.
- Enter your electricity rate per kWh (check your bill; the US average is around $0.17).
- Click Calculate Cost for kWh and dollar figures per day, month and year — plus yearly CO₂.
Electricity cost formula
Cost = kWh × Rate per kWh
Worked example
A 1,000 W air conditioner runs 5 hours a day, 30 days a month, at $1.00/kWh (illustrative rate).
Daily energy = (1,000 × 5) ÷ 1,000 = 5 kWh/day
Monthly energy = 5 × 30 = 150 kWh
Monthly cost = 150 × $1.00 = $150.00
Where the money really goes
- Heating & cooling dominate most bills — a 1,500 W space heater costs roughly 10× more per hour than a 150 W fridge.
- Always-on devices (routers, consoles on standby) add up silently; a 300 W gaming PC at 4 hrs/day is ~36 kWh/month.
- Rate matters as much as usage: the same appliance costs twice as much at $0.34/kWh (California) as at $0.17/kWh.
- Quick wins: LED bulbs (~10 W vs 60 W incandescent), shorter AC runtimes, and cold-water laundry cut kWh without lifestyle pain.
What Common Appliances Cost to Run
Tables make the formula real. Every figure below is computed with this page’s own method — watts × hours per day × 30 days, priced at $0.17 per kWh (roughly the US residential average). Swap in your own rate and the ranking stays the same, even though the dollars change.
| Appliance | Typical watts | Use per day | kWh / month | Cost / month |
|---|---|---|---|---|
| LED bulb | 10 W | 5 hours | 1.5 | $0.26 |
| Wi-Fi router | 10 W | 24 hours | 7.2 | $1.22 |
| TV (LED) | 100 W | 5 hours | 15 | $2.55 |
| Gaming PC | 300 W | 4 hours | 36 | $6.12 |
| Refrigerator (with duty cycle) | 150 W nameplate | runs ~8 effective hours | 36 | $6.12 |
| Electric dryer | 3,000 W | 1 hour | 90 | $15.30 |
| Window air conditioner | 1,000 W | 8 hours | 240 | $40.80 |
| Space heater | 1,500 W | 8 hours | 360 | $61.20 |
| EV home charger (Level 2) | 7,200 W | 2 hours | 432 | $73.44 |
Two lessons stand out. First, anything that makes heat or cold dominates: one space heater costs more than forty LED bulbs and a TV combined. Second, always-on loads are sneaky rather than huge — the router’s $1.22 a month is small, but a household of standby devices quietly adds up to a noticeable slice of the bill.
The 10-second version: cost per hour
For a quick sanity check without the full calculator, convert watts to kilowatts and multiply by your rate. A 1,500 W space heater is 1.5 kW, so at $0.17 per kWh it costs 1.5 × $0.17 ≈ 26 cents per hour. A 100 W TV costs about 1.7 cents per hour; a 10 W LED bulb, about a sixth of a cent. This per-hour view explains why heating and cooling dominate bills while lighting barely registers — and why the cheapest appliance to run is usually the one you simply switch off sooner.
The Duty-Cycle Trap: Why Your Fridge Doesn’t Run at Full Power
Many appliances cycle. A refrigerator’s compressor might be rated at 150 W, but it typically runs only about a third of the time — an average draw near 50 W, or roughly 1.2 kWh a day (36 kWh a month, about $6.12 at $0.17/kWh). Air conditioners and water heaters behave the same way once the target temperature is reached. If you enter the nameplate wattage and 24 hours for a cycling appliance, you will overestimate badly — enter the effective running hours instead, or look for the yellow EnergyGuide label, whose estimated yearly kWh already accounts for real-world cycling.
When you run an appliance can matter as much as how long. On a time-of-use plan, the same dryer load can cost noticeably more at 6 p.m. than at midnight. If your utility offers peak and off-peak rates, run the calculator twice — once per rate — for big flexible loads like laundry, dishwashers and EV charging. And to find your true rate, divide last month’s total bill by the kWh consumed: that all-in figure quietly includes the fees and delivery charges that make real bills higher than energy-only estimates.
Frequently Asked Questions
How do I find an appliance’s wattage?
Check the label on the appliance or its power brick — wattage is printed near the voltage rating. No label? Search the model number plus “watts”; manufacturer spec sheets list it. For variable devices (PCs, TVs), use typical draw rather than the maximum rating.
What is a kilowatt-hour (kWh)?
A kWh is the energy used by a 1,000-watt appliance running for one hour. Utilities bill in kWh because it captures both power and time — a 100 W bulb burning 10 hours also uses 1 kWh.
Why is my electricity bill higher than the estimate?
Estimates cover energy charges only. Real bills add fixed service fees, taxes, tiered rates (higher usage priced higher), demand charges and seasonal rate changes. Compare the kWh on your bill with the calculator’s kWh figure to isolate the gap.
What is the average US electricity rate?
Roughly $0.17 per kWh nationally, but it ranges from under $0.11 in states like Louisiana to over $0.40 in Hawaii. Always use your own bill’s rate for an accurate estimate.
kW vs kWh — what’s the difference?
kW (kilowatts) is power — the rate of energy use right now. kWh (kilowatt-hours) is energy — power sustained over time. A 1.5 kW heater running 2 hours consumes 3 kWh.
How can I lower my electricity bill?
The biggest levers: reduce heating/cooling runtime, switch to LEDs, run large appliances off-peak if your utility offers time-of-use rates, unplug standby loads, and when replacing appliances compare the yellow EnergyGuide yearly-cost labels.
What is a duty cycle, and why does it change the cost estimate?
It is the share of time an appliance actually runs at full power. Refrigerators, air conditioners and water heaters cycle on and off to hold a temperature — a fridge may run only about a third of the time. Entering nameplate watts for 24 hours overstates the cost roughly threefold; use effective running hours, or the EnergyGuide yearly kWh figure, for cycling appliances.
My appliance only lists amps and volts. How do I get watts?
Multiply volts by amps: watts = volts × amps. A device labelled 120 V and 10 A draws up to 1,200 W. Label amps are usually the maximum, so treat the result as an upper bound — typical draw for variable devices like PCs and TVs is lower.
Final Thoughts
Every figure on this page was computed live by the tool above — try your own numbers and see how the math responds.
Stop guessing what your appliances cost — run the numbers above, then check our other free household finance calculators.