How to convert Ah to Wh
Amp hours measure charge; watt hours measure energy. Because the same charge at a higher voltage carries more energy, you can only compare batteries properly in watt hours. A 100 Ah battery at 24 V stores twice the energy of a 100 Ah battery at 12 V.
Worked example
A 100 Ah LiFePO4 leisure battery has a nominal voltage of 12.8 V. 100 × 12.8 = 1,280 Wh, or 1.28 kWh. If you can use 90% of it, that's about 1,150 Wh available to run your loads.
Quick reference
| Capacity | 12 V | 12.8 V (LiFePO4) | 24 V | 48 V |
|---|---|---|---|---|
| 50 Ah | 600 Wh | 640 Wh | 1,200 Wh | 2,400 Wh |
| 100 Ah | 1,200 Wh | 1,280 Wh | 2,400 Wh | 4,800 Wh |
| 200 Ah | 2,400 Wh | 2,560 Wh | 4,800 Wh | 9,600 Wh |
| 300 Ah | 3,600 Wh | 3,840 Wh | 7,200 Wh | 14,400 Wh |
Why usable capacity matters
You rarely get the full rated energy. Lead-acid batteries last far longer if you only discharge them to about 50%, while LiFePO4 batteries are happy to go to 80–90% depth of discharge. Use the battery run time calculator to see how long that energy will power your appliances.
Frequently asked questions
How many watt hours is a 100Ah battery?
At 12 V, a 100 Ah battery holds 1,200 Wh (1.2 kWh). A 12.8 V LiFePO4 100 Ah battery holds 1,280 Wh.
Which voltage should I use?
Use the battery's nominal voltage from its label or datasheet: 12 V for a lead-acid leisure battery, 12.8 V for a 4-cell LiFePO4, 25.6 V for 24 V LiFePO4, and 3.6–3.7 V for a single lithium-ion cell.
Is Wh the same as kWh?
A kWh is 1,000 Wh. Your home electricity is billed in kWh, so dividing by 1,000 makes it easy to compare battery storage with household use.