Electricity Cost Calculator
Calculate the electricity cost of running an appliance. Enter power, hours per day, and your electricity rate.
How to use this tool
- Enter power, hours per day, number of days and electricity rate in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your total cost and the full breakdown beneath it.
Find out how much it costs to run any electrical appliance.
⚠ This tool provides general estimates for education only and is not financial, tax or legal advice. Figures may not reflect your situation — verify with a qualified professional.
Formula
Energy (kWh) = (Watts ÷ 1,000) × Hours per Day × Days
Cost ($) = Energy (kWh) × Rate ($/kWh)
How it works
The calculator converts appliance wattage to kilowatt-hours by dividing by 1,000 and multiplying by daily usage hours and the number of days. That energy figure is then multiplied by the local electricity rate to give a total cost. Results are as accurate as the inputs; actual usage may vary if the appliance cycles on and off rather than drawing constant power.
Worked example
- Convert to kW: 1,000 W ÷ 1,000 = 1 kW.
- Energy used = 1 kW × 8 h/day × 30 days = 240 kWh.
- Cost = 240 kWh × $0.25/kWh = $60.00.
Energy used: 240 kWh; Total cost: $60.00
Common mistakes to avoid
- Using the appliance's rated wattage rather than its actual draw — many devices (especially laptops and TVs) consume significantly less than their maximum rating during normal use.
- Forgetting standby or phantom load: devices left plugged in but 'off' can consume 1-10 watts continuously, adding meaningful cost over a year.
- Applying a flat rate per kWh when the utility uses tiered pricing, underestimating cost for heavy users who are charged at the higher tier.
Key terms
- Watt (W)
- The SI unit of power. It measures the rate at which an appliance consumes energy at any instant.
- Kilowatt-hour (kWh)
- The unit of electrical energy equal to consuming 1,000 watts for one hour. Utilities charge per kWh.
- Electricity rate ($/kWh)
- The price charged by a utility for each kilowatt-hour of electricity consumed. Varies by region, tariff, and time of use.
- Standby power
- Electricity consumed by a device when switched off but still plugged in. Not captured by this calculator if the device is counted as off.
- Load factor
- The ratio of actual energy consumed to the maximum possible if the appliance ran continuously. A cycling fridge has a load factor well below 1.
Frequently asked questions
- How do I calculate electricity cost?
- Multiply the appliance wattage by hours used per day and number of days, divide by 1000 to get kWh, then multiply by your electricity rate per kWh.