Electricity Cost Calculator Formula

Understand the math behind the electricity cost calculator. Each variable explained with a worked example.

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Formulas Used

Daily Cost

daily_cost = kwh_per_day * cost_per_kwh

Monthly Cost

monthly_cost = kwh_per_day * cost_per_kwh * days_per_month

Annual Cost

annual_cost = kwh_per_day * cost_per_kwh * 365

Monthly kWh

kwh_monthly = kwh_per_day * days_per_month

Variables

VariableDescriptionDefault
wattsAppliance Wattage(W)1500
hours_per_dayHours Used Per Day(hrs)4
cost_per_kwhElectricity Rate(USD/kWh)0.14
days_per_monthDays Per Month(days)30
kwh_per_dayDerived value= watts / 1000 * hours_per_daycalculated

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.

watts = 1500hours_per_day = 4cost_per_kwh = 0.14days_per_month = 30
  1. 01Daily kWh = 1,500 / 1,000 x 4 = 6.0 kWh
  2. 02Daily cost = 6.0 x $0.14 = $0.84
  3. 03Monthly cost = $0.84 x 30 = $25.20
  4. 04Annual cost = $0.84 x 365 = $306.60

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