Power Consumption Calculator
Calculate electricity usage and cost for any device.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Power Consumption Calculator
This calculator converts a device's wattage and usage hours into kilowatt-hours and electricity cost, making it easy to understand the true operating cost of any appliance or device.
- Enter device power. Find the wattage on the device label, power supply, or manual. If listed in amps at a given voltage, multiply to get watts (W = A × V).
- Enter hours per day. How many hours the device runs on an average day. Use 24 for always-on devices like routers and refrigerators.
- Enter your electricity rate. The US average is around $0.12 per kWh, but rates vary widely. Find your rate on your utility bill under "Energy Charge." The default of $0.12 is used if the field is left blank.
- Read the results. You get daily, monthly (30-day), and yearly usage in kWh plus the corresponding cost at your rate.
About Power Consumption
Energy (kWh) = Power (W) × Time (h) / 1000. A 100 W device running 8 hours per day consumes 0.8 kWh per day, 24 kWh per month, and 292 kWh per year. At $0.12/kWh, that is $2.88 per month or $35.04 per year. This calculator uses 30-day months and 365-day years for its estimates.
Standby power (phantom load) is often overlooked. Many devices draw 1 to 10 W even when "off." Enter 24 hours per day with the standby wattage to see how much standby power costs annually.
Frequently Asked Questions
How do I find the wattage of my device?
Most devices print their power rating on a label on the bottom or back. Look for "W" (watts) or "VA." If you see amps and volts instead, multiply them together (W = A × V). For devices with variable power (desktop computers, televisions), look for a "typical" wattage in the specifications, or measure with a smart plug that monitors energy.
How much does it cost to run a TV all day?
A modern 55-inch LED TV typically draws 60 to 100 watts. Running an 80 W TV for 8 hours per day at $0.12/kWh costs about $0.077 per day, $2.30 per month, or $27.74 per year. Older plasma TVs used 200 to 400 W, making them significantly more expensive to run. Use this calculator with your TV's actual wattage and local rate for a precise figure.
What is a kWh and how is it calculated?
A kilowatt-hour (kWh) is the energy used by a 1000-watt device running for one hour. It is the unit your electric utility uses to bill you. To calculate kWh: multiply watts by hours of use and divide by 1000. A 1500 W space heater running 6 hours uses 1500 × 6 / 1000 = 9 kWh. At $0.12/kWh, that is $1.08.
What is the average electricity rate in the US?
The US average residential electricity rate is approximately $0.12 to $0.15 per kWh, but it varies significantly by state. Hawaii and California have some of the highest rates (over $0.20/kWh), while Louisiana and Oklahoma have some of the lowest (under $0.10/kWh). Find your exact rate on your electricity bill under "Energy Charge" or "Rate per kWh."