Electricity Cost Calculator
Estimate what electricity costs for a given usage: cost = kWh × price per kWh. Enter energy directly, or derive kWh from watts and hours. Nothing leaves your browser.
The rate your retailer charges per kilowatt-hour (before taxes/fees, if you want a simple estimate).
How many kWh you used. Leave empty to calculate from power and time instead.
Or use average power and duration
Average load in watts. Used only if kWh is empty.
Used only if kWh is empty (with power).
Table of Contents
What this calculator does
Retail electricity is usually billed by the kilowatt-hour (kWh). If you know how much energy you used and what you pay per kWh, you can estimate the variable energy portion of your bill.
Power (watts) is a rate; energy (kWh) is power accumulated over time. One kilowatt running for one hour is 1 kWh.
This tool multiplies energy (kWh) by your price per kWh to give a simple cost estimate. You can type kWh directly (from a bill or meter) or combine watts and hours so kWh = W × h ÷ 1,000.
Actual invoices often add flat daily supply charges, time-of-use rates, discounts, and taxes. Use this calculator for quick “how much would this usage cost?” math, not as a substitute for your exact retailer statement.
Formula
Energy cost
Cost = kWh × price per kWh
Your retailer quotes price as currency per kWh (for example 0.28 per kWh). Multiply by how many kWh you used in the same period.
If you only know power and time
kWh = W × h ÷ 1,000 — then Cost = kWh × price per kWh
Example: 1,500 W for 4 h → 6 kWh. At 0.30/kWh → 1.80.
Quick Reference
| Energy (kWh) | Example rate | Cost (illus.) | Scenario |
|---|---|---|---|
| 1 kWh | 0.25 | 0.25 | One unit of energy at a sample rate |
| 10 kWh | 0.25 | 2.50 | Roughly a high-efficiency AC for part of a hot day |
| 450 kWh | 0.28 | 126.00 | Monthly household usage × sample rate (energy only) |
| 6 kWh | 0.32 | 1.92 | 1,500 W heater × 4 h |
Real-World Examples
Appliance session
A 2,400 W kettle-like load runs for 0.25 h (15 min). kWh = 2,400 × 0.25 ÷ 1,000 = 0.6 kWh. At 0.30/kWh → about 0.18 in energy.
Monthly usage from the bill
Your bill shows 380 kWh and a blended energy rate of 0.27/kWh (excluding fixed charges). 380 × 0.27 ≈ 102.60 for the variable energy component.
Space heater evening
1,500 W for 5 hours → 7.5 kWh. At 0.29/kWh → about 2.18.
EV charging
The car took 45 kWh at a home rate of 0.14/kWh → 6.30 (energy only; your tariff may differ).
FAQ
No. This tool only does kWh × your entered rate. Many bills add daily supply charges, network fees, green schemes, and tax. Add those separately if you need a full bill estimate.
For time-of-use tariffs, split your kWh by period (peak, shoulder, off-peak) and multiply each by the matching rate, then sum. This calculator assumes one average rate unless you run it per period yourself.
If you already know kWh (smart meter, bill, inverter app), enter kWh and leave power/time blank. If you know average watts and how long the load runs, leave kWh empty and use watts and hours — the tool derives kWh first.
If the kWh field has a valid positive number, that value is used for the cost. Power and time are ignored until you clear kWh. That avoids double-counting when experimenting with both inputs.
Pick a currency for display. The math is the same; only the symbol and formatting change. Enter the price per kWh in that currency.
Use the Watts to kWh Calculator to find kWh from power and time, or kWh to Watts for average power from energy — then multiply by your rate here, or enter W and h directly in this tool.