Electrical Power Consumption Calculator
Estimate how much electricity a device consumes and what it costs per month. Enter the device wattage, daily usage hours, and your utility rate to get an instant cost breakdown.
About this calculator
This calculator uses the standard energy cost formula: Monthly Cost = (Power × Hours × 30 × Rate) / 1000. Power is measured in watts, and dividing by 1,000 converts watt-hours to kilowatt-hours (kWh), which is the unit utility companies bill you for. The factor of 30 represents a typical month of daily usage. For example, a 1,500 W space heater running 8 hours a day at $0.13/kWh accumulates a significant monthly expense. Understanding this relationship helps homeowners identify energy hogs, compare appliance efficiency, and make informed decisions about usage habits or equipment upgrades.
How to use
Suppose you have a 60 W LED TV running 5 hours per day, and your electricity rate is $0.12/kWh. Plug into the formula: Monthly Cost = (60 × 5 × 30 × 0.12) / 1000 = (10,800) / 1000 = $10.80 per month. That same TV costs roughly $129.60 per year. Compare that to a 200 W older CRT TV at the same usage: (200 × 5 × 30 × 0.12) / 1000 = $36.00/month, illustrating how device efficiency directly impacts your electricity bill.
Frequently asked questions
How do I calculate the monthly electricity cost of an appliance at home?
Multiply the appliance's wattage by the number of hours you use it each day, then multiply by 30 days and your electricity rate in $/kWh, and finally divide by 1,000 to convert to kilowatt-hours. The formula is: Cost = (Watts × Hours × 30 × Rate) / 1,000. This gives you a reliable monthly estimate. Checking your utility bill for your exact rate per kWh ensures the most accurate result.
What is the average electricity cost of running a refrigerator per month?
A typical modern refrigerator uses between 100 and 400 watts and runs roughly 8–12 hours per day (accounting for compressor cycles). At $0.13/kWh, a 150 W fridge running 10 hours daily costs about (150 × 10 × 30 × 0.13) / 1,000 = $5.85 per month. Older or larger models can cost two to three times more. Energy Star-rated appliances are significantly cheaper to operate over their lifespan.
Why does dividing by 1,000 matter when calculating electricity consumption?
Utility companies charge you per kilowatt-hour (kWh), not per watt-hour. Since 1 kilowatt equals 1,000 watts, you must divide watt-hours by 1,000 to express energy in the same unit as your electricity rate. Skipping this step would overstate your cost by a factor of 1,000. This conversion is the cornerstone of any accurate electricity cost calculation and is used universally by energy monitoring tools and utility companies alike.