Ah to Watt-Hours (Wh) Converter
Battery capacity is printed in Ah (amp-hours), but to actually compare energy storage or work out backup time, you need watt-hours (Wh). This free converter does the math instantly, and the section below explains exactly why this conversion matters when comparing batteries.
Ah to Wh Converter
Convert amp-hours to watt-hours instantly.
The Formula
Watt-Hours (Wh) = Amp-Hours (Ah) × Voltage (V)
This is the most basic and important conversion in battery math. Ah only tells you how much current the battery can deliver over time, it says nothing about actual energy unless you also know the voltage. Two batteries can both be rated 100Ah, but a 12V 100Ah battery stores 1,200Wh while a 24V 100Ah battery stores 2,400Wh, double the energy, despite the identical Ah number. This is why comparing batteries by Ah alone across different voltages is misleading.
Common Ah to Wh Conversions
| Capacity | 12V | 24V | 48V |
|---|---|---|---|
| 100Ah | 1,200 Wh | 2,400 Wh | 4,800 Wh |
| 150Ah | 1,800 Wh | 3,600 Wh | 7,200 Wh |
| 200Ah | 2,400 Wh | 4,800 Wh | 9,600 Wh |
| 250Ah | 3,000 Wh | 6,000 Wh | 12,000 Wh |
Why This Matters for Buying a Battery
When comparing a 12V tubular battery against a 48V lithium battery, converting both to Wh (or kWh) is the only fair way to compare actual energy storage. It's also the first step in calculating real backup time, since usable Wh divided by your load in watts gives you hours of backup. Use our Battery Backup Time Calculator to take this a step further and factor in safe discharge depth.
Frequently Asked Questions
How many watt-hours is a 150Ah 12V battery?
A 150Ah 12V battery stores 1,800 watt-hours (150 × 12), or 1.8 kWh. Keep in mind this is the rated capacity, only about 50% is safely usable on a standard tubular or lead-acid battery.
Why do two batteries with the same Ah rating store different energy?
Because Ah alone doesn't account for voltage. A 100Ah battery at 24V stores twice the energy of a 100Ah battery at 12V, since watt-hours depend on both Ah and voltage together, not Ah alone.