Formula
Appliance wattage formula
kWh = watts x quantity x hours / 1000; cost = kWh x electricity rateActual use can be lower than nameplate wattage when appliances cycle on and off.
Appliance Wattage Calculator
Use this appliance wattage calculator to estimate what a device costs to run from its wattage and daily use.
Live calculator
Appliance wattage
Monthly energy use72 kWh
2.4 kWh per day.
Monthly cost$12.96
At 18 cents per kWh.
Annual cost$155.52
Monthly cost multiplied by 12.
Wattage is power, kWh is energy
Watts show how much power an appliance draws while running. Electric bills charge for energy, so this calculator converts watts and hours into kilowatt-hours.
Appliance energy breakdown
Power multiplied by time and converted to kWh.
| Measure | Estimate |
|---|---|
| Daily kWh | 2.4 kWh |
| Monthly kWh | 72 kWh |
| Daily cost | $0.43 |
| Monthly cost | $12.96 |
Utility estimates depend on local rates, fixed fees, taxes, runtime, billing period, and household usage. Compare against the actual bill before settling up.
How to use
Steps
- Enter the wattage listed on the appliance label or product manual.
- Enter quantity if you run more than one of the same device.
- Enter hours per day and days per month.
- Enter your electricity rate in cents per kWh.
Example
Sample calculation
Watts1,200
Use2 hours/day for 30 days
Energy72 kWh/month
At 18 cents/kWh$12.96/month
Calculator use
Best for
- Estimating home utility cost, shared bills, appliance usage, or service charges before splitting or budgeting.
- Testing usage changes such as shorter showers, different appliance cycles, rate changes, or roommate shares.
Before relying on it
Check first
- Leaving out fixed service fees, tiered rates, taxes, delivery charges, minimum bills, seasonal rates, or billing-period length.
- Using appliance labels, averages, or old bills without checking actual runtime, local rates, and household usage.
- Splitting a bill without agreeing whether fixed fees, shared rooms, guests, or unequal usage should be weighted.
Details
What to know before using the result
WattsInstant power draw
Watts describe how much power the device uses while running at that setting.
Kilowatt-hoursPower over time
Electric bills use energy over time, so watts are multiplied by hours and divided by 1,000.
Cycling appliancesAverage draw may vary
Refrigerators, HVAC, dehumidifiers, chargers, and heaters may cycle or change power levels during use.
Benchmarks
How to read the result
Under 100W: Low draw.
Common for LED lights, chargers, fans, and efficient electronics.
500W - 1,500W: High draw.
Common for heaters, microwaves, hair dryers, kettles, and some kitchen appliances.
Runs daily: Cost compounds.
Even a modest wattage can matter if it runs for many hours every day.
Calculator accuracy
Methodology and assumptions
Formula, inputs, limitations and review record
Formula
kWh = watts x quantity x hours / 1000; cost = kWh x electricity rate
Inputs used
Watts, Quantity, Hours per day, Days per month, Electricity rate
Limitations
Utility pages use visible usage and rate assumptions. Actual bills may include tiers, service fees, delivery charges, taxes, minimums, seasonal rates, and provider-specific rules.
Review record
Catalog QA baseline on June 6, 2026. This date marks the catalog-wide automated and editorial QA baseline, not a tool-specific expert review.
Cite this page
Toolkit Shelf. Appliance Wattage Calculator. https://toolkitshelf.com/tools/appliance-wattage-calculator
FAQ
Common questions
How do I convert watts to kWh?
Multiply watts by hours used, then divide by 1,000. For cost, multiply kWh by your electricity rate.
Where do I find appliance wattage?
Check the appliance label, manual, product page, or a plug-in energy meter. Some labels show amps and volts instead of watts.
Why is actual cost different?
Many devices cycle, change modes, or use less than rated wattage during normal operation. Utility rates and fees also vary.
Leave passwords, account numbers, and private medical or tax information out of your report.