HOW MANY AMP-HOURS DO YOU NEED FOR BOONDOCKING?

The formula for sizing your battery bank based on what you actually use — not what the internet says you should.

Why Amp-Hours Are the Number That Matters

Watts get the marketing headlines. Amp-hours determine whether your fridge runs at 3 AM. Your battery bank's amp-hour (Ah) rating is the amount of energy you can actually store and use between solar recharges. Get this number wrong and you'll either wake up to warm food and dead devices, or overspend on battery capacity you never touch.

The calculation isn't hard, but it requires honest accounting of what you actually use — not what you think you use, not what a YouTube vanlife channel says they use, but what your appliances, in your rig, with your camping habits actually draw.

The Amp-Hour Math

Start with your daily watt-hour budget (covered in detail in our complete system guide). Convert to amp-hours by dividing by your system voltage:

Daily Ah = Daily Wh ÷ System Voltage

For a 12V system consuming 1,500 Wh per day: 1,500 ÷ 12 = 125 Ah per day.

But you don't want a battery bank sized to exactly one day's use. You need a buffer for:

• Cloudy days: At least one day of reserve (2× daily use) if you boondock in variable weather.
• Depth of discharge: Even LiFePO4 batteries last longer when you don't drain them to 0% every day. Keeping above 20% extends cycle life significantly.
• Inverter losses: If you run AC appliances, the inverter consumes 10–15% of the energy passing through it. Factor that into your daily use number.

The Practical Formula

Battery bank (Ah) = Daily Ah × Days of Autonomy ÷ Max Depth of Discharge

For 125 Ah/day, 1.5 days of autonomy, and 80% max DoD (LiFePO4):

125 × 1.5 ÷ 0.80 = 234 Ah. Round to 200 Ah (two 100Ah batteries) for a budget build or 300 Ah (three 100Ah) for comfortable headroom.

Common Boondocking Loads by Amp-Hour Draw

Here's what your appliances actually cost in amp-hours on a 12V system:

*Inverter loads include ~15% conversion loss.

LiFePO4 vs AGM: The Amp-Hour Trap

A 100Ah AGM battery does not give you 100 amp-hours of usable power. It gives you 50 Ah — because you can only safely discharge AGM to 50% before permanent damage begins. A 100Ah LiFePO4 battery gives you 80–100 Ah of usable power (80–100% depth of discharge).

This means a 200Ah LiFePO4 bank provides the same usable energy as a 400Ah AGM bank — at less than half the weight. When someone says "I need 400Ah for boondocking" without specifying chemistry, ask them which kind. The answer changes the entire system design.

Building in Buffer: One Day or Two?

One day of autonomy (total bank = ~1.5× daily use) works if you camp in consistently sunny locations (Southwest desert, southern plains) and have enough solar to fully recharge on a clear day. This is the minimum for comfortable boondocking.

Two days of autonomy (total bank = ~2.5× daily use) is the comfortable standard for boondockers who camp in variable weather (mountains, Pacific Northwest, shoulder seasons) or who don't want to monitor their battery percentage anxiously. It covers a full cloudy day without lifestyle changes.

Three days of autonomy is overkill for most RVers and adds significant cost and weight. Only consider this if you camp in extended overcast conditions (Alaska, Pacific Northwest winter) with no generator backup.

Real-World Battery Bank Examples

Here are three actual boondocking setups from RVers who've dialed in their power budgets through real measurement rather than spreadsheet estimates.

Solo weekender in a teardrop trailer: LED lights, phone charging, small portable fan. Measured daily draw: forty-two amp-hours. Battery bank: one hundred-amp-hour LiTime LiFePO4. Solar: single hundred-watt panel. Result: arrives home with sixty to seventy percent battery remaining after two nights, even on partly cloudy days. The system is deliberately oversized for the use case, which means zero energy anxiety.

Couple in a travel trailer, seven-day BLM stays: Twelve-volt fridge, LED lights, two phones, laptop, MaxxAir fan, water pump. Measured daily draw: one hundred ten amp-hours. Battery bank: two hundred-amp-hour Renogy LiFePO4 (two hundred-amp-hour batteries in parallel). Solar: four hundred watts. Result: batteries reach full charge by early afternoon on sunny days, maintaining sixty to seventy percent overnight. Cloudy days draw the bank down to forty percent but recover the next sunny day.

Full-timer in a Class A, continuous boondocking: Full-size twelve-volt fridge, LED lights, two laptops (remote workers), TV, CPAP machine, Instant Pot twice daily, MaxxAir fan. Measured daily draw: two hundred twenty amp-hours. Battery bank: four hundred-amp-hour Victron Smart LiFePO4. Solar: eight hundred watts. Result: system keeps up in summer and high-sun regions. In winter or Pacific Northwest overcast, a Honda generator supplements solar for two to three hours every other day. The generator is the pressure valve that makes the rest of the system work year-round.