Electricity Cost Calculator
Calculate how much an appliance or device costs to run per day, month, and year based on its power rating and your electricity rate. Use it to compare appliances, spot energy hogs, or estimate bill impact before buying a new device.
About this calculator
Electricity cost depends on how much power a device consumes, how long it runs, and what you pay per kilowatt-hour (kWh). Power in watts is divided by 1,000 to convert to kilowatts, then multiplied by daily hours of use and 365 days to get annual energy consumption in kWh. Multiplying by the electricity rate gives the annual cost in dollars. An efficiency factor (≥1) is divided out to account for devices that are not 100% efficient—for example, an older refrigerator may have an efficiency factor of 1.1, increasing its effective cost. Formula: Annual Cost = (power_rating / 1000) × hours_per_day × 365 × electricity_rate / efficiency_factor. Divide by 365 for daily cost, or multiply daily cost by ~30.4 for monthly cost.
How to use
Example: A 1,500 W space heater runs 6 hours/day, electricity rate = $0.13/kWh, efficiency factor = 1.0. Step 1 — Convert to kW: 1,500 / 1,000 = 1.5 kW. Step 2 — Daily energy: 1.5 × 6 = 9 kWh/day. Step 3 — Annual energy: 9 × 365 = 3,285 kWh. Step 4 — Apply efficiency: 3,285 / 1.0 = 3,285 kWh. Step 5 — Annual cost: 3,285 × $0.13 = $426.93/year. Daily cost: $426.93 / 365 ≈ $1.17/day.
Frequently asked questions
How do I calculate the monthly electricity cost of running an appliance?
Multiply the appliance's wattage by your daily hours of use, then divide by 1,000 to get daily kWh. Multiply daily kWh by 30.4 (average days per month) to get monthly kWh, then multiply by your rate in $/kWh. For example, a 100 W TV running 5 hours/day uses 0.5 kWh/day × 30.4 = 15.2 kWh/month × $0.13 = $1.98/month. Checking your electricity bill for your actual rate per kWh gives the most accurate result, as rates vary widely by location and time of use.
What is the average electricity cost per kWh in the United States?
As of 2024, the U.S. residential average electricity rate is approximately $0.16–$0.17 per kWh, though it varies significantly by state—Hawaii pays over $0.38/kWh while Louisiana averages around $0.11/kWh. Your specific rate also depends on your utility's tiered pricing, time-of-use plans, and fixed charges. Always use the rate shown on your most recent electricity bill for the most accurate cost estimate. Many utilities also charge demand charges and fees that can raise your effective per-kWh cost.
Why does the efficiency factor increase the calculated electricity cost?
An efficiency factor greater than 1.0 indicates that a device consumes more energy than its nameplate rating suggests under real-world conditions, or that it has energy losses (heat, friction, conversion losses). Dividing by a factor greater than 1.0 increases the cost, correctly reflecting higher actual consumption. For example, an older air conditioner rated at 1,000 W but operating with an efficiency factor of 1.2 effectively costs as much to run as a 1,200 W device. Newer, high-efficiency appliances may have efficiency factors close to 1.0, while aging or poorly maintained equipment can exceed 1.3.