Electricity Cost Calculator
Estimate appliance running cost, kWh use, and monthly or yearly power spend with this electricity cost calculator before you leave a heater, AC unit, desktop, or other plug load running longer than planned.
Calculator Inputs
Enter the appliance load, daily runtime, rate, and how many days you use it in a typical month.
Quick presets
Main Result
Review the monthly estimate first, then use the secondary cards to check the active-day cost and projected yearly spend.
Secondary Result
Open the audit trail for the current formula substitution, input values, and the 24/7 comparison view.
Secondary Result
Open the audit trail for the current formula substitution, input values, and the 24/7 comparison view.
Current calculation
Formula substitution for the displayed monthly result
cost = (watts / 1000) x hours x electricity rate
1. Convert watts to kilowatts: 100 W / 1000 = 0.100 kW
2. Active-day energy: 0.100 kW x 8.0 hours = 0.80 kWh
3. Active-day cost: 0.80 kWh x $0.1600 = $0.13
4. Monthly projection: $0.13 x 30 usage days = $3.84
At $0.1600 per kWh, a 100 W appliance used 8.0 hours on each day of use for 30 days per month costs about $3.84 per month and $46.08 per year.
Input audit
24/7 comparison
If the same wattage ran continuously, the cost would be $0.38 per full day.
Using your current monthly day count, that would project to $11.52 per month.
This is an alternate scenario for comparison, not the cost of your entered daily runtime.
Use Scenarios
Appliance check
Estimate appliance running cost before long daily use
Use the electricity cost calculator when you want a fast appliance running cost estimate for a space heater, dehumidifier, window AC, desktop, or other device you might leave on for hours at a time.
Bill planning
Turn wattage and usage into a monthly bill estimate
This page works well as a simple kWh cost calculator when you know the device wattage and your utility rate and want to see how one load changes the monthly and yearly bill picture.
Comparison
Compare two schedules or two devices
Run one setup, note the monthly cost, then change either the wattage or the daily runtime to compare a smaller fan against a heater, or part-time use against all-day operation.
Formula Explanation
Step 1
Convert watts to kilowatts
kW = watts / 1000
Electric utilities bill energy in kilowatt-hours, so the first step is to convert the appliance nameplate or measured wattage into kilowatts.
Step 2
Calculate one active day of energy use
daily kWh = kW x hours per day
This shows the energy used on one day of operation based on the runtime you entered. It is the cleanest starting point for every later cost projection.
Step 3
Apply your electricity rate
daily cost = daily kWh x rate per kWh
Once the page knows how many kWh the appliance uses in one day of operation, it multiplies that energy by your rate to get the active-day cost.
Step 4
Scale by usage days per month
monthly cost = daily cost x usage days; yearly projection = monthly cost x 12
Monthly and yearly outputs assume your entered monthly usage pattern repeats. That keeps the result aligned with your own schedule instead of forcing every appliance into a 365-day model.
How to Read the Result
Primary output
Monthly cost is the planning anchor
The headline card answers the most common question: how much this appliance adds to a typical month when it runs with the schedule and rate you entered.
Daily context
Per active day shows the cost of one day of use
Read the daily figure as the cost of one day the appliance actually runs. It helps compare part-time and all-day schedules without mixing them into the monthly assumption.
Projection note
Yearly is a schedule-based projection
The yearly number extends your monthly usage pattern across 12 months. For seasonal appliances such as air conditioners or heaters, rerun the calculator with the months you expect to use it.
Example Cases
Worked example
Case 1: LED desk lamp used every evening
Inputs
- Appliance wattage: 10 W
- Hours per day: 6
- Electricity rate: $0.1600/kWh
- Usage days per month: 30
Computed Results
- Per active day: $0.01
- Monthly cost: $0.29
- Yearly projection: $3.46
- Monthly energy: 1.80 kWh
Interpretation
This is a good baseline for a small continuous household load. The electricity cost calculator shows that low-wattage devices usually matter less individually, but they can still stack up when several run every day.
Decision Hint
Use a case like this to separate minor plug loads from the bigger devices that deserve most of your bill-reduction attention.
Worked example
Case 2: Desktop setup used on workdays
Inputs
- Appliance wattage: 250 W
- Hours per day: 8
- Electricity rate: $0.1600/kWh
- Usage days per month: 22
Computed Results
- Per active day: $0.32
- Monthly cost: $7.04
- Yearly projection: $84.48
- Monthly energy: 44.00 kWh
Interpretation
Here the monthly result stays moderate because the schedule only applies on workdays. That makes the page useful for office equipment, tools, or study setups that are not on every day of the month.
Decision Hint
If your schedule changes between workdays and weekends, keep the monthly day count realistic instead of assuming the equipment runs every calendar day.
Worked example
Case 3: Window AC during a warm month
Inputs
- Appliance wattage: 1200 W
- Hours per day: 8
- Electricity rate: $0.2000/kWh
- Usage days per month: 30
Computed Results
- Per active day: $1.92
- Monthly cost: $57.60
- Yearly projection: $691.20
- Monthly energy: 288.00 kWh
Interpretation
Higher-wattage comfort equipment moves the monthly cost much faster than lighting or electronics. This kind of example shows why an appliance electricity cost calculator is often most useful for heating and cooling loads.
Decision Hint
If a cooling or heating device looks expensive here, rerun the page with fewer hours, a different thermostat strategy, or a more efficient appliance to see the tradeoff.
Boundary Conditions
Sources & References
- U.S. Department of Energy - Estimating Appliance and Home Electronic Energy UseUsed for the page guidance on estimating electricity use from wattage, runtime, and measured appliance behavior when the nameplate rating is not the full story.
- U.S. Energy Information Administration - Electricity Data and StatisticsUsed as the factual reference for utility-bill context such as kWh billing and the reality that electricity rates can vary meaningfully by provider, plan, and region.