100Ah vs 200Ah vs 300Ah Battery for a Van or RV: Which Do You Need?
The most common sizing question for a van or RV electrical system is whether to go with 100Ah, 200Ah, or 300Ah of house battery. Here's how to make the call with real numbers instead of guesses.
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Enter your appliances and we'll calculate the watt-hours, recommend an Ah size, and link to US products — free.
What the numbers actually mean
All three refer to amp-hours at 12V. To compare them on equal footing, convert to watt-hours — the universal unit:
| Bank size | Total Wh | Usable Wh (LiFePO4, 80%) | Usable Wh (AGM, 50%) |
|---|---|---|---|
| 100Ah | 1,280Wh | ~1,024Wh | ~512Wh |
| 200Ah | 2,560Wh | ~2,048Wh | ~1,024Wh |
| 300Ah | 3,840Wh | ~3,072Wh | ~1,536Wh |
This is why LiFePO4 is the default for van builds: a single 100Ah LiFePO4 delivers the same usable energy as two 100Ah AGMs, at about half the weight.
When 100Ah is enough
A 100Ah LiFePO4 bank (~1,024Wh usable) works for:
- Weekend van trips where you're near a plug every few days
- Minimal loads: LED lighting, phone and laptop charging, a small fan
- A 12V compressor fridge on short trips (but you'll want to drive or plug in every day to top it back up)
- Builds where a portable power station handles the heavy lifting
Typical daily usage at this level: 400–700Wh
US picks: LiTime 100Ah ($220), Renogy 100Ah LiFePO4 ($280)
100Ah gets tight fast
Add a CPAP (240Wh/night), a fridge (480Wh/day), and a laptop (180Wh) and you're already at 900Wh — nearly the full usable capacity of a 100Ah bank, with nothing left for lights or charging. Most people who start at 100Ah wish they'd gone to 200Ah.
When 200Ah is the right call
A 200Ah LiFePO4 bank (~2,048Wh usable) is the sweet spot for most part-time and moderate full-time van builds. It covers:
- A 12V compressor fridge running 24/7
- LED lighting
- Laptop, phone, tablet charging
- A CPAP without a heated humidifier
- A vent fan running most of the day and night
- 1–2 days of autonomy before recharging (with solar or DC-DC)
Typical daily usage: 700–1,400Wh
US picks: LiTime 200Ah ($399), Battle Born 200Ah ($1,198 — premium build quality and US support), Renogy 200Ah LiFePO4 (~$550)
When 300Ah+ makes sense
A 300Ah+ bank (~3,072Wh usable at 300Ah) is for full-timers and heavy users:
- Induction cooking regularly (1,200–1,800W per use)
- Larger 12V fridges or dual-zone fridges
- Running a significant inverter load — hair dryer, coffee maker, power tools
- Rigs without reliable solar or DC-DC that need 2+ days of autonomy
- Large van or skoolie builds with multiple people
Typical daily usage: 1,500–2,500Wh+
US picks: LiTime 300Ah ($599), two LiTime 200Ah in parallel ($799), Battle Born 270Ah (~$1,399)
Two 100Ah vs one 200Ah
Two 100Ah batteries wired in parallel gives you the same total capacity as one 200Ah at a similar price. The practical differences:
- One 200Ah: simpler wiring, single cell, easier to manage
- Two 100Ah in parallel: redundancy (if one fails, you still have half capacity), flexibility to add more later, more common in existing builds
Either works. If you're starting fresh, the single 200Ah is often cleaner. See how to wire batteries in parallel for the correct wiring method.
The sizing formula
If you want to calculate your exact need:
- Add up daily Wh (watts × hours for each appliance)
- Divide by 0.8 (LiFePO4 usable fraction)
- Divide by 12.8 (nominal voltage) to get Ah
- Multiply by your desired days of autonomy (1.5–2 for most builds)
- Round up to the nearest standard size
Full sizing walkthrough: what size house battery for a van or RV?
Don't forget charging
A 300Ah bank with a tiny solar setup or no DC-DC charger will stay half-empty most of the time. Match your battery size to your charging plan — see the solar setup guide and charging systems guide to make sure you can actually fill whatever bank you buy.