How many watt-hours in a 100Ah battery?
A 12 V 100Ah LiFePO4 battery (12.8 V nominal) holds 1,280 Wh — 1.28 kWh — of which about 1,024 Wh is usable at 80% depth of discharge. A 12 V 100Ah lead-acid battery holds 1,200 Wh, about 600 Wh usable at 50%.
How to work it out
- 100 Ah × 12.8 V = 1,280 Wh (1.28 kWh)
- Usable at 80% depth of discharge: 1,024 Wh (80 Ah)
A 100Ah battery is the standard building block of van, boat and RV systems, and both lithium and lead-acid versions are sold with that number on the label. The amp-hours match; the usable energy does not.
Adjust for your project
More options: DoD
- In kWh
- 1.28 kWh
- Usable energy at your depth of discharge
- 1,024 Wh
- Usable amp-hours
- 80 Ah
Common battery sizes at the voltage above
| Battery capacity | Energy | In kWh | Usable energy at your depth of discharge |
|---|---|---|---|
| 50 | 640 Wh | 0.64 kWh | 512 Wh |
| 100 | 1,280 Wh | 1.28 kWh | 1,024 Wh |
| 200 | 2,560 Wh | 2.56 kWh | 2,048 Wh |
| 280 | 3,584 Wh | 3.58 kWh | 2,867 Wh |
| 300 | 3,840 Wh | 3.84 kWh | 3,072 Wh |
| 400 | 5,120 Wh | 5.12 kWh | 4,096 Wh |
What a 100Ah battery really gives you
- Lithium is 12.8 V, not 12. Four LiFePO4 cells at 3.2 V each make 12.8 V nominal, which is why the lithium battery has 80 more watt-hours on paper.
- Lead-acid gives about half the usable energy. Trojan recommends 20–50% discharge for long life, so 600 Wh out of 1,200 is the planning figure. LiFePO4 at 80% gives 1,024 Wh — 1.7 times as much from the same label.
- Heavy loads shrink lead-acid further. Trojan’s group 27 battery delivers 105 Ah over 20 hours but only 85 Ah over 5 hours. At inverter-sized currents it is lower still.
- Physical size. Crown’s lithium 100 Ah battery is a group 24 case, and Crown’s 12 V lead-acid batteries in groups 24 to 31 range from 75 to 115 Ah — the battery group size chart lists them.
How long does 1,024 Wh last? How long a 100Ah battery runs a fridge and how long a 100Ah battery lasts with a 1000W inverter cover the two extremes. Two of them? See how many watt-hours in a 200Ah battery.
Different size? Use the full Amp-Hours to Watt-Hours Calculator.
What you’ll need
- 12 V 100 Ah LiFePO4 batteryPremium price
About 1.28 kWh rated in a box roughly the size of a group 24–31 lead-acid battery at around half the weight. Check the BMS discharge limit and whether it can charge below freezing.
See options on Amazon (opens in a new tab) - 12 V deep cycle AGM batteryMid-range price
Sealed lead-acid with no watering. Cheaper up front than lithium, but plan to use only about half its rating and expect it to weigh roughly twice as much.
See options on Amazon (opens in a new tab) - Battery monitor with shuntMid-range price
Counts amp-hours in and out, so you see true state of charge instead of guessing from voltage — which barely moves on a LiFePO4 battery until it is nearly empty.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How many watt-hours is a 12 V 100Ah lead-acid battery?
1,200 Wh rated, about 600 Wh usable at 50% depth of discharge.
How many kWh is a 24V 100Ah battery?
2.56 kWh for a 25.6 V LiFePO4, about 2,048 Wh usable at 80%.
How many kWh is a 100Ah battery?
1.28 kWh for a 12.8 V LiFePO4 (1.2 kWh for a 12 V lead-acid).
Other common sizes
- How many watt-hours in a 200Ah battery — 2,560 Wh (12.8 V LiFePO4) or 2,400 Wh (12 V lead-acid)
- A 48V 100Ah battery in kWh — 5.12 kWh (about 4.1 kWh usable)
Sources
- Victron Energy — Lithium Battery Smart manual, technical data (opens in a new tab) — LiFePO4 12.8 V: cycle life 2,500 at 80% DoD, 3,000 at 70%, 5,000 at 50% (to 80% of capacity); 92% round-trip efficiency; 12.8 V 100 Ah: recommended continuous discharge ≤100 A (1C), maximum 200 A; capacity about 20% lower at 0 °C; charge only between +5 °C and +50 °C.
- Trojan Battery — Technical support FAQs (opens in a new tab) — “We generally recommend a discharge of 20 to 50% of the battery’s rated capacity even though the battery is capable of being cycled to 80%”; 20-hour and 100-hour ratings; freezing points by state of charge.
- Trojan Battery — 27TMX data sheet (opens in a new tab) — Group 27 flooded: 85 Ah (5-hr), 97 Ah (10-hr), 105 Ah (20-hr), 117 Ah (100-hr); state of charge vs open-circuit voltage table; charger settings.
- Crown Battery — Deep Cycle Battery Product Specifications (effective Oct 1, 2024) (opens in a new tab) — 20-hour capacities by BCI group for flooded, AGM and lithium 12 V batteries.