kWh Cost Calculator

How It Works

Electricity is billed by the kilowatt-hour (kWh), which is 1,000 watts used for one hour. Knowing an appliance wattage and how long you run it lets you calculate the exact cost on your power bill.

The Formula

Variables

• Watts — Power consumption of the appliance (found on its label or manual)
• Hours — Number of hours the appliance runs per day
• kWh — Kilowatt-hours -- the billing unit on your electric bill
• Rate — Your utility rate in dollars per kWh (check your bill)

Example

A 1,500W space heater running 8 hours/day: 1,500 x 8 / 1,000 = 12 kWh/day. At $0.15/kWh that costs $1.80/day, $54/month, or $648/year.

Tips

• Your electricity rate is on your utility bill -- look for the per-kWh charge.
• Phantom loads (devices on standby) can add 5-10% to your bill. Use power strips to kill standby draw.
• LED bulbs use about 80% less energy than incandescent -- switching all your lights saves $100+ per year.
• Running a space heater full-time is one of the most expensive appliance habits. Consider a programmable thermostat instead.
• Time-of-use rates mean electricity costs more during peak hours (typically 4-9 PM). Shift heavy usage to off-peak times.