The formula
Daily usage (kWh) = Power (W) Γ· 1000 Γ Daily usage hours
Monthly cost = Daily usage Γ Days used Γ Your electricity rate (per kWh)
Electricity rates vary widely by country, utility provider, plan, and usage tier (many places use tiered or time-of-use pricing). Enter your own actual rate from a recent bill for the most accurate estimate.
Typical appliance wattages (for reference)
- LED desk lamp: about 10-20W
- Refrigerator: about 100-200W (runs all day)
- Home air conditioner: about 1,000-2,000W
- Microwave: about 700-1,200W
- Hair dryer: about 1,000-1,800W
Actual power draw varies by product and model, so check the rated wattage on the appliance's label or manual for the most accurate figure.
Frequently Asked Questions
Does this account for tiered electricity pricing?
No β this calculator applies a single flat rate you provide. Many utilities charge different rates depending on how much electricity you use in a billing period, so check your actual bill for the precise total.
What's the difference between W (watts) and kWh (kilowatt-hours)?
A watt (W) measures instantaneous power, while a kilowatt-hour (kWh) measures the total energy used over time. For example, running a 1000W appliance for 1 hour consumes 1 kWh.