Electricity Calculator
Energy Cost Estimator
Result
| Time Period | Energy (kWh) | Cost ($) |
|---|---|---|
| Per Day | — | — |
| Per Month (30.4 days) | — | — |
| Per Year | — | — |
How to Use This Electricity Calculator
That space heater label says 1500 watts, but your utility bill speaks kilowatt-hours—and connecting the two in your head while standing in the hardware aisle never feels straightforward. I use this whenever I want to know what an appliance actually costs to run daily, monthly, or yearly before committing to buy or leave plugged in.
- Enter Power Consumption. Type wattage or kilowatt rating and select Watts (W) or Kilowatts (kW).
- Enter Hours of Use Per Day. Type average daily runtime in hrs/day.
- Enter Energy Price (per kWh). Use your utility rate in dollars per kWh from your bill.
- Press Calculate Cost. Review Energy (kWh) and Cost ($) for Per Day, Per Month (30.4 days), and Per Year.
Assumes constant daily usage—fine for refrigerators, servers, and heaters left on predictable schedules. For circuit-level voltage and current math, use the Ohm's Law Calculator. For whole-trip fuel costs on the road, see the Fuel Cost Calculator.
Electricity Calculator Formulas and Practical Applications
Utility billing revolves around the kilowatt-hour (kWh)—power over time.
kW = Watts ÷ 1000
Daily kWh = kW × Hours per Day
Daily Cost = Daily kWh × Rate ($/kWh)
Monthly Cost = Daily Cost × 30.4167
Yearly Cost = Daily Cost × 365
Example: 1500 W heater, 4 hours/day, $0.15/kWh → 1.5 kW × 4 = 6 kWh/day → $0.90/day → ~$27/month → ~$328/year.
Typical Appliance Reference
- LED bulb (10 W): 5 hrs/day at $0.15/kWh ≈ $0.008/day
- Refrigerator (150 W avg): 24 hrs/day ≈ $0.54/day at $0.15/kWh
- Window AC (900 W): 8 hrs/day ≈ $1.08/day at $0.15/kWh
Frequently Asked Questions
Where do I find my electricity rate?
Check your utility bill for the total charge divided by total kWh used that period—that blended rate works for estimates. Time-of-use plans have different peak and off-peak rates; use the rate for when you actually run the appliance.
Should I enter nameplate wattage or actual draw?
Nameplate maximum is conservative (overestimates cost). For accuracy on variable-load devices like refrigerators or PCs, a plug-in power meter gives real average draw over 24 hours.
Why does the month use 30.4167 days?
That is the average days per month (365.25 ÷ 12), giving a smoother monthly estimate than assuming exactly 30 days.
Can I enter power in kilowatts?
Yes. Select Kilowatts (kW) in the Power Consumption unit dropdown, or enter watts with Watts (W) selected—the calculator converts to kW internally before computing kWh.
Does this include taxes or fixed utility fees?
No. Results cover variable energy cost from power, daily hours, and your $/kWh rate only. Delivery charges, taxes, and monthly minimums are billed separately on most statements.