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Kilowatts to Amp Hours Calculator
Enter power, voltage, and hours to calculate battery capacity in amp hours.
Amp Hours Result
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Enter values to calculate
Formula Used
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Watts
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Milliamps
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Horsepower
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kWh
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How Kilowatts to Amp Hours Works
1
Enter the power in kilowatts (kW)
This is the average power draw of the load you want to run on battery power.
2
Enter the battery voltage
Common battery voltages: 12V (car/RV), 24V (marine/solar), 48V (off-grid/data center), 51.2V (LiFePO4 packs).
3
Enter the duration in hours
How long do you need the load to run? This determines the total amp hours required.
4
Read the amp hours (Ah)
This is the minimum battery capacity needed. For lead-acid batteries, multiply by 2 (50% depth of discharge). For lithium, multiply by 1.25 (80% DoD).
Kilowatts to Amp Hours Formula
kW to AhAh = (kW × 1000 × Hours) ÷ V
Multiply power in watts by hours, then divide by voltage.
kWh to AhAh = (kWh × 1000) ÷ V
If you know kilowatt-hours, multiply by 1000 and divide by voltage.
Usable CapacityRequired Ah = Ah ÷ DoD
Divide by depth of discharge (0.5 for lead-acid, 0.8 for lithium) to get the total battery size.
The formula to convert kilowatts to amp hours is Ah = (kW × 1000 × Hours) ÷ V.
For example, running a 0.5 kW load for 4 hours on a 12V battery requires: Ah = (0.5 × 1000 × 4) ÷ 12 = 166.67 Ah. For a lead-acid battery (50% DoD), you need a 333 Ah battery. For a lithium battery (80% DoD), you need a 208 Ah battery.
Amp hours measure battery capacity — how much current a battery can deliver over a period of time. A 100 Ah battery can theoretically deliver 100 amps for 1 hour, or 10 amps for 10 hours.
Frequently Asked Questions
Amps measure instantaneous current flow. Amp hours (Ah) measure total charge over time. 1 Ah = 1 amp flowing for 1 hour.
1 kWh at 12V equals 83.33 Ah. Formula: (1 × 1000) ÷ 12 = 83.33 Ah.
Calculate Ah from your kW load and runtime hours. Then divide by depth of discharge (0.5 for lead-acid, 0.8 for LiFePO4) to get the total battery bank size.
Not without knowing the duration. Kilowatts measure power (rate), while amp hours measure capacity (total). You need the runtime in hours.
DoD is how much of the battery capacity you actually use. Lead-acid batteries should not be discharged below 50% (DoD = 0.5). Lithium batteries can safely go to 80% (DoD = 0.8).