RV Solar & Battery Calculator — Size Your Off-Grid System

How much battery and solar does your RV actually need? Check the appliances you run, set how many days you want to camp without hookups, and this calculator sizes your LiFePO4 battery bank, solar array, and the matching Victron MPPT charge controller — using the same math we use to spec systems for Black Series and other off-road campers.

How the sizing works

Three rules drive every off-grid power system: plan around amp-hours per day (not watts on a label), size the battery so your trip fits inside the usable capacity (LiFePO4 gives you 85%+, lead-acid only 50%), and size solar to replace a full day's use in the sun you actually get — not brochure conditions. That's why the calculator applies a 75% harvest derate: controller efficiency, panel temperature, and imperfect sun angles all take their cut.

Frequently asked questions

Is this calculator only for Victron gear?

No — the amp-hour and watt math applies to any brand. We link Victron because it's the system we stock, install guidance exists for it across our blog, and the components integrate into one monitored system.

What if I camp with hookups most of the time?

Size for your longest realistic off-grid stretch, not your average. A system that covers a 2-day boondock handles everything shorter.

Do I need an inverter?

Only for 120V AC appliances (microwave, induction, coffee maker, most TVs). If everything you run is 12V, skip the inverter and its idle draw.