Boondocking Water & Battery Calculator

A typical family of four uses 20 to 40 gallons of fresh water per day including showers, dishes, toilet, and drinking. A 40-gallon tank usually lasts 1 to 2 days. Conservative campers who use navy showers and paper plates can stretch 40 gallons to 3 or 4 days. The calculator above adjusts for your habits.

A single 100Ah lead-acid battery gives you about 50Ah of usable power (you should never drain below 50%). That runs an RV fridge, LED lights, and a phone charger for about 24 hours. Lithium batteries can use 80 to 100 percent of capacity. Add solar or a generator to extend your stay.

The RV absorption fridge (on 12V or inverter), the furnace fan, a coffee maker, a microwave, and a hair dryer are the biggest draws. LED lights and phone chargers barely matter. Running a 1500W appliance for 1 hour uses about 125Ah — more than a whole battery bank.

Not with a typical rental setup. An RV AC draws 1,500 to 2,000 watts and would drain a small battery bank in under an hour. Boondocking with AC requires a large lithium bank (300+ Ah), a 3,000W inverter, and significant solar — usually only on owner rigs.

Yes. Just enter your van fresh water tank size, battery amp-hours, and appliance list. Class B camper vans often have smaller tanks (20 to 25 gal) and single 100Ah batteries, so plan for 1 to 2 days off-grid unless you add portable solar.