kWh Cost Calculator
Estimate the exact expense of operating electrical devices. Converts nameplate wattage and usage hours into kilowatt-hours (kWh) and dollars based on your local utility tariff.
Continuous wattage rating from product label
Average operating hours per 24-hour day
Electric utility rate per kilowatt-hour (US average ~$0.16/kWh)
Estimated cost added to your monthly utility bill
How to Use This Calculator
- Find the appliance wattage on its UL specification tag.
- Enter the estimated hours the device is powered on each day.
- Enter your utility rate per kWh from your electric bill.
- Review projected daily, monthly, and annual operating costs.
Formula & Calculation Methodology
Power in watts multiplied by operating hours gives watt-hours, divided by 1,000 to obtain kilowatt-hours (kWh). Multiplying by your electric tariff gives the monetary expense.
Worked Example
1500W Space Heater (4 Hours/Day)
100W Always-On PC Setup (24 Hours/Day)
Frequently Asked Questions
Where do I find my electricity rate per kWh?↓
Look at the electricity supply and delivery charges on your monthly bill, and divide total dollars by total kWh used.
Do refrigerators run at full wattage 24 hours a day?↓
No, compressor appliances cycle on and off (duty cycle of roughly 35% to 50%), running around 8 to 12 active hours per day.
What is phantom power consumption?↓
Electronics in standby mode consume small amounts of power (vampire load), averaging 5% to 10% of residential electric use.
How much does an LED light bulb cost to run?↓
A 9W LED running 4 hours a day consumes 0.036 kWh/day, costing roughly $0.17 per month at $0.16/kWh.
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Source Citation & Disclaimer
Informational tool only; not licensed tax, legal, or financial advice.