Energy formula tool
Watts and kWh Calculator
Convert between watts, operating hours, and kWh; 1,500 W for 8 hours equals 12 kWh before cost or load comparisons.
Convert Watts, Runtime, and kWh
Calculate energy from power and runtime: 1,500 W for 8 hours uses 12 kWh, or estimate average watts from kWh and hours.
Result
kWh
12 kWh
Result notes
Keep the entered values, assumptions, and result together when adding this calculation to job notes or submittal records. Final installation choices should align with the applicable code edition, equipment listing, manufacturer instructions, local amendments, and AHJ requirements.
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Formula and field context
Convert between watts, operating hours, and kWh; 1,500 W for 8 hours equals 12 kWh before cost or load comparisons.
Formula context
Energy and kWh Conversion Chart
Energy is power over time. Convert watts to kilowatts by dividing by 1,000, then multiply by hours to get kWh. Use this chart as the unit worksheet, and use the calculator result when runtime, duty cycle, appliance assumptions, and utility rate need to be recorded together.
Formula
kWh = W x hours / 1000. Wh = W x hours. Cost = kWh x utility rate.Variables to keep with the result
- W is load power in watts.
- hours is runtime for the period being estimated.
- kWh is kilowatt-hours used for most energy billing calculations.
- utility rate is the cost per kWh supplied by the user.
Formula and variables
Energy in kWh equals watts multiplied by hours and divided by 1,000. The reverse estimate multiplies kWh by 1,000 and divides by operating hours to find average watts. This is an energy-use relationship, not a demand-charge or power-quality calculation.
U.S. field example
A 1,500 W load running for 8 hours uses 12 kWh. If the effective rate is known, that kWh value can move into a cost worksheet. If the load cycles on and off, use average power or duty-cycle adjusted runtime instead of the equipment maximum rating.
When to use a broader calculator
Use the energy calculator when daily, monthly, and annual use all need to be modeled together. Use the electricity-cost calculator when rates, billing periods, and cost comparisons become the main task.