20Ah to Wh — 240 Wh at 12V
20Ah stores 240 Wh at 12V, 480 Wh at 24V, and 960 Wh at 48V. Below: usable energy per chemistry, what it runs, and how the same energy is built from standard modules.
20Ah at 12V is 240 Wh — that is 0.24 kWh of nameplate energy.
Formula: Wh = Ah × V. The voltage is the nominal battery voltage, not the charging voltage.
A real LiFePO4 module of 20Ah is usually labelled 256 Wh, because its nominal voltage is 12.8V rather than a round 12V. Both 240 Wh and 256 Wh describe the same battery.
Result
Energy in Wh equals capacity in Ah multiplied by battery voltage. 1000 Wh equals 1 kWh.
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Design Your SystemAt every system voltage
The same capacity stores four times the energy at 48V that it does at 12V, and draws a quarter of the current for the same load.
| System voltage | Capacity | Energy | kWh |
|---|---|---|---|
| 12 V | 20 Ah | 240 Wh | 0.24 |
| 24 V | 20 Ah | 480 Wh | 0.48 |
| 48 V | 20 Ah | 960 Wh | 0.96 |
How much of it you can actually use
Nameplate energy is not usable energy. Depth of discharge caps what you may take out before you damage the battery, and it differs by chemistry.
| Chemistry | Depth of discharge | Usable energy | Usable capacity | Cycles at that DoD |
|---|---|---|---|---|
| LiFePO4 | 80 % | 192 Wh | 16 Ah | ~3,500 |
| AGM | 50 % | 120 Wh | 10 Ah | ~600 |
| Gel | 50 % | 120 Wh | 10 Ah | ~800 |
| Flooded lead-acid | 50 % | 120 Wh | 10 Ah | ~400 |
What that runs
Runtime from the usable LiFePO4 energy at 12V (80% depth of discharge), one load at a time, no inverter losses on the DC rows.
| Load | Power | Runtime |
|---|---|---|
| LED lighting | 15 W | 12.8 h |
| 12V compressor fridge (average) | 45 W | 4.3 h |
| Diesel heater (fan and glow plug average) | 30 W | 6.4 h |
| Water pump (while running) | 65 W | 3 h |
| Laptop plus router | 75 W | 2.6 h |
| Kettle through an inverter | 1200 W | 0.2 h |
What this size is in practice
20Ah is the small-block class: fish finders, gate openers, small shed solar, and the internal packs of compact power stations. At 48V it is also the size most light e-mobility packs are quoted in, which is why "48V 20Ah" is searched far more often than any other 20Ah pairing.
Building the same energy from standard modules
How many standard 100Ah 12V modules add up to this energy, and what capacity that becomes at each system voltage.
| System voltage | Capacity | Standard modules |
|---|---|---|
| 12 V | 20 Ah | 1 x 100Ah / 12V |
| 24 V | 10 Ah | 1 x 100Ah / 12V |
| 48 V | 5 Ah | 1 x 100Ah / 12V |
Other capacities (Ah)
Other energy values (Wh)
FAQ
How many Wh is 20Ah?
20Ah is 240 Wh at 12V, 480 Wh at 24V, and 960 Wh at 48V. Multiply the amp-hours by the nominal battery voltage: Wh = Ah × V.
How much of that 240 Wh can I use?
On LiFePO4 at 80% depth of discharge you get 192 Wh (16 Ah at 12V). On AGM or gel at 50% you get 120 Wh (10 Ah). Same nameplate, very different usable energy.
How long does that run a 12V fridge?
A compressor fridge averaging 45 W runs about 4.3 hours on the usable LiFePO4 energy at 12V. Cycling depends on ambient temperature, so treat this as the upper bound for a well-insulated unit.
Why does the datasheet say 256 Wh instead of 240 Wh?
Because LiFePO4 has a nominal voltage of 12.8V per 12V module, not exactly 12V. 20Ah × 12.8V = 256 Wh. The 12V figure of 240 Wh is the conservative system-voltage calculation. Both describe the same battery.
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