What You Need to Know About Van Solar
Solar is the most reliable way to keep your battery charged when you’re off-grid. But wattage claims, rigid vs flexible, and “peak sun hours” make it easy to overbuy or underbuy. Here’s the framework that works.
Key specs that matter
- Rated power (W): What the panel can produce in ideal conditions. Real-world output is usually 60–80% of that. 200W is a sweet spot for many vans; 400W+ if you run a fridge, inverter, and devices daily.
- Rigid vs flexible: Rigid panels are more efficient and last longer (20–25 years), but need a flat or angled roof and mounting hardware. Flexible panels stick to curved roofs and are lighter, but typically have a shorter lifespan (around 5–15 years) and slightly lower efficiency.
- Charge controller: You need one between the panels and your battery. PWM is cheaper; MPPT is more efficient (especially in cloud or cold). Match the controller’s max input voltage and current to your array.
- Voltage (12V vs 24V): Most van systems are 12V. “12V” panels (often ~18V max power) work with 12V batteries via a charge controller. Don’t wire panels directly to the battery.
How to choose
Start with your daily power use (in watt-hours), then work backward to panel size and type. These steps keep it simple.
Step 1: Estimate your daily consumption
Add up fridge, lights, phone/laptop charging, pump, and anything else. A typical van might use 50–150 Wh per day (minimal) to 500–1,000+ Wh (fridge, inverter, etc.). Your battery size and solar need to cover that plus some margin.
Step 2: Size solar to your battery and location
Rough rule: 1W of solar per 1–2 Ah of battery is a starting point; 200W for a 100Ah battery is common. If you’re in cloudy or northern latitudes, lean toward more watts. If you also charge via alternator or shore power, solar can be smaller.
Step 3: Decide rigid vs flexible
Rigid: Best if you have a flat or angled roof and want max efficiency and longevity. You’ll need brackets and possibly tilting hardware.
Flexible: Best for curved roofs, low profile, or when you don’t want heavy framing. Expect a shorter lifespan and a bit less output per square foot.
Step 4: Match your charge controller
MPPT controllers get more energy from the same panels, especially in non-ideal conditions. Ensure the controller’s max input voltage and current exceed your array’s. Many “solar kits” include a suitable controller.