Electricity Cost Calculator Formula
Understand the math behind the electricity cost calculator. Each variable explained with a worked example.
Formulas Used
Daily Cost
daily_cost = kwh_per_day * cost_per_kwhMonthly Cost
monthly_cost = kwh_per_day * cost_per_kwh * days_per_monthAnnual Cost
annual_cost = kwh_per_day * cost_per_kwh * 365Monthly kWh
kwh_monthly = kwh_per_day * days_per_monthVariables
| Variable | Description | Default |
|---|---|---|
watts | Appliance Wattage(W) | 1500 |
hours_per_day | Hours Used Per Day(hrs) | 4 |
cost_per_kwh | Electricity Rate(USD/kWh) | 0.14 |
days_per_month | Days Per Month(days) | 30 |
kwh_per_day | Derived value= watts / 1000 * hours_per_day | calculated |
How It Works
How to Calculate Electricity Cost
Convert wattage to kilowatts, multiply by usage hours to get kWh, then multiply by your utility rate.
Formula
Daily kWh = Wattage / 1000 x Hours Per Day
Daily Cost = kWh x Rate Per kWh
Worked Example
A 1,500W space heater running 4 hours/day at $0.14/kWh.
- 01Daily kWh = 1,500 / 1,000 x 4 = 6.0 kWh
- 02Daily cost = 6.0 x $0.14 = $0.84
- 03Monthly cost = $0.84 x 30 = $25.20
- 04Annual cost = $0.84 x 365 = $306.60
Frequently Asked Questions
How do I find my electricity rate?
Check your utility bill for the cost per kilowatt-hour (kWh). The US average is about $0.12-$0.16/kWh, but rates vary widely by state and provider.
What appliances use the most electricity?
Space heaters, air conditioners, water heaters, dryers, and ovens are typically the biggest energy users. Always check the wattage on the appliance label.
How do I reduce electricity costs?
Use LED bulbs, unplug idle devices, use a programmable thermostat, wash clothes in cold water, and replace old appliances with Energy Star rated ones.
Ready to run the numbers?
Open Electricity Cost Calculator