RV & Van Life Solar Calculator - Battery Bank & Panel Sizing | SolarRatio
Calculate solar system requirements for RV, van, and camper van builds. Enter daily consumption to find battery capacity, panel wattage, and recommended panel count.
RV solar sizing balances the unique constraints of mobile off-grid living: limited roof real estate, fixed-tilt mounting, weight-sensitive battery placement, hot summer travel days, cold winter boondocking, and intermittent driving recharge from the alternator. The right system supports a fridge, vent fans, LED lighting, water pump, induction or microwave cooking, laptops, Starlink, and CPAP — without daily generator runs and without unbalanced loads that prematurely kill a 200–300 Ah LiFePO4 house bank. Popular US boondocking destinations like the Texas hill country, Colorado high country, and BLM land in the Southwest average 5.5–6.5 h/day PSH in summer — excellent solar conditions — but the same rigs wintering in the Pacific Northwest or New England face 3–4 h/day, requiring a conservatively sized battery bank to bridge cloudy stretches.
How it Works
Start with a Wh/day load profile separated by season and travel style (boondocking heavy vs frequent driving). Divide by worst-case PSH (often 3.5–4 in 4-season travel) and a flat-mount efficiency derate of 0.7 (lower than ground-mount because RV roofs cannot tilt). The result is recommended array W. Battery sizing then uses Wh/day × autonomy days ÷ DoD ÷ 12V (or 24V for larger rigs). The tool also recommends DC-DC alternator charger amperage to recharge during 2–3 hour driving legs without overloading the OEM alternator (typically capped at 40–60 A for stock; 70–100 A for upgraded). Pair with a 2,000–3,000 W pure-sine inverter for induction cooking and a multi-stage shore-power charger for 30-amp pedestal hookups.
Usage Scenarios
Full-time class C RVers boondocking across the US Southwest spec a 600 W rooftop array, 300 Ah 12V LiFePO4 bank, 2,000 W inverter, and 40 A DC-DC charger to sustain indefinite boondocking with a residential fridge and AC inverter cooking. Weekend van-life travelers run leaner — 200 W array, 100 Ah 12V LiFePO4, 1,000 W inverter — designed around 2–3 day stays with frequent driving recharge. Travel-trailer owners upgrade from the factory 100 W panel to a 400 W flexible array bonded to a curved roof, paired with a 200 Ah LiFePO4 retrofit. Skoolie converters build 24V systems with 800–1,200 W of tilt-mounted panels and 600 Ah LiFePO4 for full residential loads. Truck-camper minimalists use a 200 W portable suitcase array deployed at camp to extend a 100 Ah battery's autonomy.
Frequently Asked Questions
How much solar do I need on my RV roof?
Start with your daily watt-hour load, then divide by worst-case peak sun hours (often 3.5–4 for four-season travel) and a flat-mount derate of about 0.7, since RV roofs cannot tilt. A 1,800 Wh/day load needs roughly 700W. Boondockers commonly run 400–600W; weekend vans run 200W.
What size battery bank should I pair with my RV solar?
Size battery in watt-hours: daily load times autonomy days, divided by depth of discharge and bank voltage. For 1,800 Wh/day, two days autonomy, 80% DoD on 12V LiFePO4, that's about 375 Ah, so a 300–400 Ah bank. Cloudy-region winter travel needs more autonomy and capacity.
Do I need MPPT or PWM for an RV solar setup?
Use MPPT for almost all modern RV systems. It harvests 15–30% more than PWM, especially in cold weather and when panel voltage exceeds battery voltage, which is typical with higher-voltage panels feeding a 12V bank. PWM only makes sense for very small, low-cost setups with closely voltage-matched panels.
Can my RV alternator recharge the house batteries while driving?
Yes, with a DC-DC charger that protects the alternator. Stock alternators are usually capped at 40–60A of charge current; upgraded ones support 70–100A. A 40A DC-DC charger adds meaningful charge during a 2–3 hour driving leg, complementing solar and reducing reliance on a generator while traveling.
What inverter size do I need to cook or run AC in an RV?
Induction cooktops and microwaves need a 2,000–3,000W pure-sine inverter, and an inverter air conditioner can require similar surge handling. Match inverter capacity to your largest simultaneous load plus motor startup surge, and ensure your battery bank can deliver that current without sagging or tripping low-voltage protection.
How to Use the RV & Van Life Solar Calculator
Enter your daily power consumption (Wh), battery voltage (12V or 24V), days of autonomy, and depth of discharge. Formula: Battery capacity (Ah) = daily Wh × autonomy days / (DoD% × voltage).
Enter peak sun hours for your travel region and system efficiency. Formula: Required panel watts = daily Wh / (peak sun hours × efficiency). The calculator also shows how many 100W, 200W, or 400W panels you need.
RV defaults: 12V system, LiFePO4 DoD 80%, 2 days autonomy. Use the regional presets for sun hours: sunny regions ~6h, temperate ~4.5h, cloudy ~3h. Size up your battery and panels by 20% for safety margin.