How to use this calculator
A nameplate wattage tells you power draw, but not what that power costs over time. Enter how long the appliance actually runs and your electricity rate to translate watts into a household budget estimate.
- Find watts on the appliance label or manual.
- Enter active run time, not merely time plugged in.
- Use your bill's effective per-kWh rate when available.
FORMULA
The math behind the estimate
watts × hours used × quantity ÷ 1,000 = kWh. Multiply kWh by the electricity rate for cost.
Worked example
A 1,200 W appliance used for one hour a day at $0.18/kWh uses 36.5 kWh and costs about $6.57 in an average month.
Change the defaults to model your home. The result is an estimate, not a guaranteed bill or savings promise.
How to read the result
Use the estimate to compare scenarios and find the inputs worth measuring more carefully. Utility bills can include fixed charges, taxes, delivery fees, minimums, tiers, and demand charges that are not fully represented by a simple energy rate.
Assumptions and limitations
- Power draw is constant while running.
- An average month is 30.4375 days.
- Standby draw is excluded unless included in watts and time.
Climate, equipment condition, installation, controls, and household behavior can materially change results. Verify consequential installation and purchasing decisions with qualified providers.
Practical savings context
Measure actual runtime first. Timers, smart plugs, and efficient replacements matter most when an appliance runs often.
SOURCE
Data and methodology
U.S. Department of Energy — Estimating Appliance Energy Use
Methodology accessed August 2026. Geographic scope: United States. Last reviewed: August 6, 2026.
WattMeasure uses the source to frame the method and assumptions; your editable inputs determine the displayed result.
QUESTIONS
Any appliance FAQ
How accurate is this appliance estimate?
It is a planning estimate based on the values you enter. Actual power draw, cycling, utility charges, climate, and equipment condition can change the result.
Should I use the default electricity rate?
Your own marginal or all-in supply rate is better. Check a recent bill or your utility's published rate schedule.
Does this include taxes and utility fees?
Only when they are reflected in the rate you enter. Fixed monthly charges are not included because they usually do not change with one appliance's usage.
Last reviewed August 6, 2026 · Data update policy