Two 100 Ah LiFePO4 batteries is the answer for most vans. Here's the math that says whether your build is "most vans."
The inverter-only version of this question is what size battery bank for a 2000W inverter.
Ah = (Wh/day × days × 1.25) ÷ 12 ÷ 0.80
The examples below use 12 V and 0.80. Days = autonomy before recharging.
Those inputs, written as six steps with this page’s 1,500 Wh light-van example, are on how to calculate battery bank size.
Everything hinges on the honest watt-hour audit. Van loads are small individually and relentless collectively: the fridge never turns off, and it's the anchor of every load list.
This page does not publish a measured van load list. The light example is 1,500 Wh/day and the full-timer example is 3,000 Wh/day. Both are inputs to the formula, the same rows as the table below. A diesel heater's published current is on the diesel heater battery page, not an average invented here.
(1,500 × 1 × 1.25) ÷ 12 ÷ 0.80 = 195.3125 Ah, about 195 Ah at 12 V, which two 100 Ah batteries cover. (3,000 × 1 × 1.25) ÷ 12 ÷ 0.80 = 390.625 Ah, about 391 Ah at 12 V, four 100 Ah batteries. The same 3,000 Wh at 48 V is (3,000 × 1 × 1.25) ÷ 48 ÷ 0.80 = 97.656 Ah, about 98 Ah. Series wiring does not multiply amp-hours.
| Build | Daily use | Ah needed | Typical hardware | Cost* |
|---|---|---|---|---|
| Weekend/light | 1.5 kWh | 195 Ah | 2 × 100 Ah | $550–1,600 |
| Full-timer | 3.0 kWh | 391 Ah | 4 × 100 Ah | $1,100–3,200 |
*Price is for the listed number of 100 Ah batteries: count × $269.99 to $799.00, rounded to the nearest $50. Low is the Redodo 12V 100Ah at $269.99; high is the Battle Born BB10012 at $799.00. Checked 2 Oct 2026. LiTime $302.39 and SOK $369.00 sit inside that span. Renogy lists $356.99 and was unavailable, so it is not an endpoint. Hardware is the smallest whole count of 12V 100Ah batteries that covers the Ah (195→2, 391→4).
The 1.25 is this site's margin. It is not a manufacturer rating. The 0.80 is the LiFePO4 planning depth of discharge on this site. Skipping either factor changes the amp-hour result relative to every other page here.
As an Amazon Associate I earn from qualifying purchases. The Amazon links below are affiliate links; they don't change the math.
The rows above count 100 Ah LiFePO4 batteries at 12 V.
100 Ah LiFePO4 on Amazon → 2,000W inverters on Amazon → 12V fridges on Amazon →
The battery count only matters if you can refill the watt-hours you use. Driving, solar, and shore power are the usual sources. Size each one from the charger or array you actually have. This page does not publish a charge rate or a solar yield.
More sizing: the battery bank sizer directory, the cabin-specific version in what size battery bank for an off-grid cabin, and the charging side at GeneratorSizer ↗ / SolarSizer ↗.
More sizing: the battery bank sizer directory, the cabin-specific version in what size battery bank for an off-grid cabin, and the charging side at GeneratorSizer ↗ / SolarSizer ↗.
A light weekend build (1.5 kWh/day: fridge, lights, fan, phones) needs about 195 Ah at 12V LiFePO4 — two 100 Ah batteries. A full-timer build (3 kWh/day, 1 day of autonomy) needs about 391 Ah at 12V, four 100 Ah batteries.
One 100 Ah battery covers the day only when the formula on this page comes out at or under 100 Ah. The light row is 1,500 Wh/day, which is about 195 Ah, so two 100 Ah batteries. Put your own measured watt-hours into the formula rather than a guessed appliance list.
This page does not publish a fridge wattage. A 100 Ah battery at 12 V is 1,200 Wh nameplate. Divide the usable watt-hours (nameplate times 0.80 on the LiFePO4 rows) by the fridge's measured daily watt-hours.
The examples on this page are 12 V. The same watt-hours at a higher voltage are a smaller amp-hour number. Series wiring does not multiply amp-hours.
A 100 Ah battery at 12 V and 0.80 depth of discharge is 960 Wh usable (100 × 12 × 0.80). Divide 960 by the fridge's measured daily watt-hours. This page does not supply that watt-hour figure.
Full-time off-grid instead of van life? The same formula at what size battery bank for an off-grid cabin covers cabin-scale autonomy math, and the battery bank size calculator directory maps daily use to Amp-hours at every voltage. A bank that sits unused loses charge on a different schedule: how long a battery holds a charge. Below freezing, the charger cutoff is on the lithium charger page. The 50% DoD count is the AGM guide.
Sources for the 2 Oct 2026 price checks and for depth of discharge and cycle life:
Yes — free to use, no signup, no email required.
Estimates follow industry-standard sizing rules and common safety margins. Always confirm with a licensed professional for final sizing.
Yes — the page is fully responsive and works on phones, tablets, and desktop.