Battery & energy
Electricity Cost Calculator
Electricity cost equals energy used in kilowatt-hours multiplied by your price per kilowatt-hour. Daily, monthly, and annual estimates normalize the entered billing period.
Calculate electricity cost from energy use, billing-period length, and your own price per kilowatt-hour.
Calculated result
Estimated electricity cost
Calculating…
Calculated locally in your browser
Planning math only. Verify equipment specifications and installation requirements separately.
What this calculator returns
Use the effective rate from your bill if you want variable charges reflected; fixed charges require separate treatment.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
Cost = energy in kWh x price per kWh; daily, monthly, and annual estimates normalize the entered period by days.
- W
- Average real power in watts.
- h
- Operating or charging time in hours.
- kWh
- Accumulated electrical energy in kilowatt-hours.
- rate
- User-entered electricity price per kilowatt-hour.
- η
- User-entered efficiency expressed as a decimal or percentage.
Energy is measured in kilowatt-hours, rate is your planning price per kWh, and days is the measurement period.
Worked example
| Input | Value |
|---|---|
| Energy used | 900 kWh |
| Period length | 30 days |
| Electricity rate | 0.15 $/kWh |
Using 900 kWh over 30 days at $0.15/kWh gives a $135 period cost and about $4.50 per day.
Reference table
| Use case | Energy | At $0.15/kWh | At $0.30/kWh |
|---|---|---|---|
| 1 kW for 1 hour | 1 kWh | $0.15 | $0.30 |
| 1.5 kW for 4 hours | 6 kWh | $0.90 | $1.80 |
| 30 kWh EV session | 30 kWh | $4.50 | $9.00 |
| 900 kWh billing period | 900 kWh | $135.00 | $270.00 |
Frequently asked questions
How do watts and hours become kWh?
Multiply watts by operating hours and divide by 1,000; then multiply kWh by the entered electricity rate.
Does this include fixed utility charges?
No. The result models energy charges from the entered rate and does not add taxes, demand charges, minimum bills, or fixed fees.
Which electricity rate should I use?
Use the price per kWh that matches your purpose. An all-in effective rate can include variable bill charges, while a supply-only rate will not.
Assumptions and limitations
- No utility-rate database, tier, tax, demand-charge, or fixed-fee model.
- Monthly and annual values are normalized planning estimates.
Method and sources
Review the electrical formulas, calculation methodology, and standards status for the references most relevant to this calculation. The broader technical sources index records source scope and verification. Last reviewed .