Van & RV Solar Setup (US): Sizing, Panels & Wiring 2026

Solar is what makes a van or RV truly off-grid: park anywhere with sky overhead and your battery refills for free. This guide covers how much solar you need, how to wire it, and how to pick an MPPT charge controller — for US conditions and US gear.

Solar feeds your battery, so size that first: see the house battery guide.

How much solar do you need?

Solar output depends on peak sun hours — the equivalent hours of full-strength sun per day. This varies a lot across the US: the desert Southwest averages 5.5–6+ in summer, while the Pacific Northwest or Northeast in winter can be 2–3.

A practical sizing formula:

Solar watts ≈ daily Wh ÷ (peak sun hours × 0.75 system efficiency)

Example: 1,200Wh/day ÷ (4.5 × 0.75) ≈ 355W → round to a 400W array.

Plan around the worst conditions you'll actually camp in, not the best. If you travel south for winter, you can size smaller; if you stay north, size up or lean more on DC-DC and shore charging.

Rigid vs. flexible panels

• Rigid (framed) panels are the most efficient and durable, and run cooler thanks to an air gap. Best for most metal roofs. Brands: Renogy, Rich Solar, Newpowa.
• Flexible panels conform to curved roofs (fiberglass high-tops) and are low-profile, but run hotter and typically don't last as long. Use them when a rigid panel won't fit.

MPPT, not PWM

Always use an MPPT (maximum power point tracking) charge controller, not a cheap PWM unit — MPPT harvests 20–30% more energy and handles higher array voltages. Size the controller to your array:

• A Victron SmartSolar 100/30 (~$159) handles up to ~440W at 12V.
• A Victron SmartSolar 100/50 (~$228) handles up to ~700W at 12V.

The "100" is the maximum PV input voltage; make sure your array's cold-weather open-circuit voltage stays under it (more below).

Series vs. parallel wiring

• Series (panels chained + to −) adds voltage, keeps current low, and means thinner wire and less voltage drop — great for longer roof runs. But the string voltage must stay under the controller's limit even on cold mornings (open-circuit voltage rises in the cold).
• Parallel (all + together, all − together) keeps voltage low and adds current — more tolerant of partial shade, but each string needs its own fuse and you'll need thicker wire.

A common 12V setup is two panels in series into a 100V MPPT. The calculator checks the cold-voltage math for you and recommends the wiring.

Wiring essentials

• Use UV-rated solar cable (typically 10 AWG) with MC4 connectors for roof runs.
• Add a PV disconnect/breaker between the array and the controller.
• With parallel strings, add an inline MC4 fuse on each string positive.
• Keep an air gap under rigid panels — heat reduces output.

Related guides

• House battery guide
• Charging systems guide — pair solar with DC-DC and shore
• Wiring & safety guide

FAQ

How many watts of solar do I need for a van?

Most US van builds run 200–600W. As a rule of thumb, divide your daily watt-hours by about 3.4 (4.5 peak sun hours × 0.75 efficiency) to get the array size. A typical full-timer at ~1,200Wh/day needs around 400W. Use the calculator for a precise figure.

Will solar alone keep my battery charged?

In sunny regions and for moderate use, often yes. But cloudy stretches, winter, and heavy shade reduce output, so most builders pair solar with a DC-DC charger (for travel days) and sometimes shore power. See the charging systems guide.

Series or parallel for van solar panels?

Series reduces voltage drop and wire size and suits longer roof runs, as long as the cold-weather string voltage stays under your MPPT's limit. Parallel handles partial shade better but needs string fuses and thicker wire. Two panels in series into a 100V MPPT is a common, safe default.