Electricity calculator
Electric Bill Calculator
Estimate monthly electricity cost from appliance watts, daily hours, billing days, and your local kWh rate.
When to use this calculator
Use this calculator when you want to understand how one appliance or device affects a monthly electric bill. It is useful for heaters, fans, televisions, pumps, gaming PCs, dryers, dehumidifiers, and any appliance with a wattage label.
The estimate is strongest when you use the rate from your own electricity bill and a realistic usage schedule. The label wattage is only the starting point; thermostats, timers, standby modes, cycling compressors, and user behavior can change the real cost.
Formula used
kWh = watts ÷ 1,000 × hours per day × days. Cost = kWh × electricity rate.
The formula is intentionally simple so it can be used for quick planning. Real bills, quotes, and installation costs can include fixed fees, taxes, tiers, labor, product limits, and site-specific conditions that a calculator cannot see.
Input guide
| Input | How to use it |
|---|---|
| Watts | The appliance power rating. Use the label, manual, product page, or a plug-in watt meter. |
| Hours per day | The realistic daily running time, not the maximum possible running time. |
| Days | The number of days in the bill period or planning period. |
| Electricity rate | Your price per kWh, including delivery charges if you want a closer all-in estimate. |
Examples
Space heater example
A 1,500 W heater running 4 hours a day for 30 days uses 180 kWh. At $0.17/kWh, the monthly cost is $30.60.
Ceiling fan example
A 70 W fan running 8 hours a day for 30 days uses 16.8 kWh. At $0.17/kWh, the monthly cost is about $2.86.
How to get a more accurate result
- Use your latest bill rate instead of a national average.
- Run separate estimates for summer and winter if usage changes by season.
- For variable appliances, measure real kWh with a plug meter when possible.
Common mistakes to avoid
- Entering kilowatts as watts, for example typing 1.5 instead of 1500.
- Assuming an AC, fridge, or pump pulls rated wattage every minute.
- Ignoring fixed utility fees that appear on the bill even when usage is low.
Quick checklist before relying on the result
- Check the appliance label.
- Confirm your kWh rate.
- Estimate actual daily use.
- Compare low, normal, and heavy-use scenarios.
FAQ
Is the calculator exact?
No. It is a planning estimate. Actual bills can include taxes, tiers, delivery charges, demand charges, or seasonal pricing.
Should I use rated watts or measured watts?
Use measured watts when available. Rated watts are good for quick comparison but can overstate or understate real usage.
Can I compare two appliances?
Yes. Run the same hours, days, and rate for both appliances, then compare monthly cost.