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Battery Runtime

Ah to Wh Calculator

Convert amp-hours to watt-hours, watt-hours to amp-hours, and either to kWh, for any battery voltage. Use it to compare batteries with different voltages or to read a power station’s rating as amp-hours.

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Quick answer

Watt-hours = amp-hours × volts. A 12 V 100 Ah battery holds 1,200 Wh (1.2 kWh). To go back, divide by the voltage: 1,000 Wh at 12 V is 83.3 Ah.

Convert Ah to Wh

Convert from
Ah
V

Use the nominal voltage on the label: 3.6–3.7 V for a lithium-ion cell or power bank, 12.8 V for a 12 V LiFePO4 battery.

Capacity in watt-hours

1,200 Wh

100 Ah at 12 V

Amp-hours
100 Ah
Milliamp-hours
100,000 mAh
Watt-hours
1,200 Wh
Kilowatt-hours
1.2 kWh

100 Ah × 12 V = 1,200 Wh

How to convert amp-hours to watt-hours

Multiply the amp-hours by the battery voltage:

Wh = Ah × V

Example: a 24 V 200 Ah battery bank stores 200 × 24 = 4,800 Wh, or 4.8 kWh. For milliamp-hours, divide by 1,000 first, or use the mAh to Wh calculator.

How to convert watt-hours to amp-hours

Divide the watt-hours by the voltage:

Ah = Wh ÷ V
Ah = kWh × 1,000 ÷ V

Example: a 2,048 Wh LiFePO4 power station built on a 12.8 V battery holds 2,048 ÷ 12.8 = 160 Ah. The voltage must be the battery’s own voltage, not the 120 V or 230 V of the AC outlets.

Ah to Wh conversion chart

Watt-hours for common battery sizes at the nominal voltages they are sold at. 12.8 V and 51.2 V are the real voltages of “12 V” and “48 V” LiFePO4 batteries.

Capacity12 V12.8 V24 V48 V51.2 V
7 Ah84 Wh90 Wh168 Wh336 Wh358 Wh
9 Ah108 Wh115 Wh216 Wh432 Wh461 Wh
20 Ah240 Wh256 Wh480 Wh960 Wh1,024 Wh
50 Ah600 Wh640 Wh1,200 Wh2,400 Wh2,560 Wh
100 Ah1,200 Wh1,280 Wh2,400 Wh4,800 Wh5,120 Wh
150 Ah1,800 Wh1,920 Wh3,600 Wh7,200 Wh7,680 Wh
200 Ah2,400 Wh2,560 Wh4,800 Wh9,600 Wh10,240 Wh
280 Ah3,360 Wh3,584 Wh6,720 Wh13,440 Wh14,336 Wh
300 Ah3,600 Wh3,840 Wh7,200 Wh14,400 Wh15,360 Wh

kWh to Ah chart for home and solar batteries

Home batteries are rated in kilowatt-hours. This is the same capacity in amp-hours at each system voltage.

Energy12 V24 V48 V51.2 V
1 kWh83 Ah42 Ah21 Ah20 Ah
2.5 kWh208 Ah104 Ah52 Ah49 Ah
5 kWh417 Ah208 Ah104 Ah98 Ah
10 kWh833 Ah417 Ah208 Ah195 Ah
13.5 kWh1,125 Ah563 Ah281 Ah264 Ah
15 kWh1,250 Ah625 Ah313 Ah293 Ah

Why compare batteries in watt-hours

Amp-hours only compare batteries of the same voltage. A 24 V 100 Ah battery stores twice the energy of a 12 V 100 Ah battery, though both say “100 Ah”. Watt-hours measure energy directly, so they let you compare a 12 V RV battery, a 48 V home battery and a portable power station on equal terms, and they plug straight into a runtime estimate: runtime (h) ≈ usable Wh ÷ load (W).

  • Rated is not usable. The Wh figure is the rated capacity. You can use about 90% of it from LiFePO4 and about 50% from lead-acid if you want it to last.
  • Series adds volts, parallel adds amp-hours. Two 12 V 100 Ah batteries hold 2,400 Wh whichever way they are wired: 24 V 100 Ah in series or 12 V 200 Ah in parallel.

Once you have watt-hours, the battery runtime calculator tells you how long they will run a load, and the battery capacity calculator works out how many you need. The method is on how battery runtime is calculated.

Frequently asked questions

How many watt-hours is a 100Ah battery?

It depends on the voltage. A 12 V 100 Ah lead-acid battery holds 1,200 Wh, a 12.8 V 100 Ah LiFePO4 battery 1,280 Wh, a 24 V 100 Ah battery 2,400 Wh and a 48 V 100 Ah battery 4,800 Wh (4.8 kWh).

How do I convert watt-hours to amp-hours?

Divide the watt-hours by the battery voltage: Ah = Wh ÷ V. A 1,000 Wh power station with a 12.8 V battery inside holds about 78.1 Ah; a 1,000 Wh battery at 24 V is about 41.7 Ah.

How many amp-hours is a 5 kWh battery?

A 5 kWh battery at 48 V holds about 104 Ah, and at the 51.2 V of a 16-cell LiFePO4 home battery about 97.7 Ah. The same 5 kWh at 12 V would be about 417 Ah. Multiply kWh by 1,000 and divide by the voltage.

Is a 12V 100Ah battery 1,200 Wh or 1,280 Wh?

Both are used. Lead-acid batteries have a nominal 12 V, so 100 Ah is 1,200 Wh. LiFePO4 batteries sold as “12 V” are really 12.8 V (four 3.2 V cells), so 100 Ah is 1,280 Wh. Use the voltage printed on the battery label for an exact figure.

Can I convert Ah to Wh without knowing the voltage?

No. An amp-hour measures charge and a watt-hour measures energy, and voltage links the two (watts = amps × volts). The same 100 Ah is 370 Wh in a 3.7 V lithium-ion pack and 4,800 Wh in a 48 V battery bank. If you only know the battery type, use its nominal voltage: 1.2 V for NiMH, 3.6–3.7 V for lithium-ion, 3.2 V per LiFePO4 cell, 2 V per lead-acid cell.