electrical tool
kWh Calculator
Calculate daily and period energy use from load and schedule.
Energy = watts × hours per day × days ÷ 1000. The selected period is the number of days entered.
Energy use
360 kWh
Daily energy: 12 kWh. Selected period: 30 days.
Energy use guide
Understand watts, kilowatts, and kWh
Watts describe power at a moment in time. Kilowatts are watts divided by 1,000. A kilowatt-hour, or kWh, measures how much energy a load uses over a period.
Formula
kWh = (watts × hours) ÷ 1,000
For a repeated daily load, multiply the daily result by the number of days in the selected period.
Worked examples
Daily: A 1,000 W load used for 2 hours uses (1,000 × 2) ÷ 1,000 = 2 kWh.
30-day period: The same load used 2 hours daily uses 2 × 30 = 60 kWh.
Example energy table
| Load | Hours/day | Daily kWh |
|---|---|---|
| 100 W | 8 | 0.80 kWh |
| 500 W | 4 | 2.00 kWh |
| 1000 W | 2 | 2.00 kWh |
Practical uses
Use kWh estimates to compare schedules, understand energy use over a billing period, and provide the energy input for an electricity-cost estimate. The result is not an instantaneous wattage or startup rating.
Frequently asked questions
What is the difference between watts and kWh?
Watts measure instantaneous power. A kilowatt-hour measures energy used over time.
How do I calculate kWh?
Multiply watts by hours and divide by 1,000. For repeated daily use, multiply by the number of days in the selected period.
How do I estimate monthly energy?
Enter the daily hours and the number of days in your period. The calculator multiplies watts × hours per day × days ÷ 1,000.
Does kWh tell me the appliance's peak power?
No. kWh measures accumulated energy and does not describe startup or instantaneous power demand.
Important assumptions
This is a planning estimate, not a guarantee of performance. Real equipment varies with temperature, age, power quality, duty cycle, wiring, and manufacturer specifications.