A reliable solar system is the single most important upgrade you can make to a van build. Get it right and you'll run lights, charge devices, power a fridge, and never worry about shore power. Get it wrong and you'll be running your engine every morning just to brew coffee.
This guide covers everything from calculating your power needs to final wiring — written for people doing their first build, not electricians.
Step 1: Calculate Your Power Needs
Before buying a single panel, you need to know how much power you actually use. List every device you plan to run, its wattage, and how many hours per day you'll use it.
A typical van setup looks something like this:
- Fridge (12V compressor fridge like a BougeRV or Dometic) — 40–60Wh per day
- Phone charging x2 — 20Wh per day
- Laptop — 60–80Wh per day
- LED lighting — 10–20Wh per day
- Fan (Maxxair or Fan-Tastic vent fan) — 15–40Wh per day depending on speed
Add it up: most van lifers use between 100–250Wh per day. Double that number to get your battery capacity target (you never want to drain a lithium battery below 50%, or a lead-acid below 80%).
Step 2: Choose Your Battery Type
Lithium (LiFePO4) batteries are now the standard choice for van builds. They're more expensive upfront but last 3–5x longer, are significantly lighter, and can be discharged to 20% without damage.
For most builds: 100–200Ah of lithium is the sweet spot. A 100Ah LiFePO4 battery gives you roughly 80–90Ah of usable capacity — enough for a fridge, lights, and device charging for a full day with minimal sun.
Budget builds: AGM lead-acid batteries work, but you need twice the capacity to get the same usable power, and they're far heavier. For a starter setup on a tight budget, a single 100Ah AGM battery can work, but plan to upgrade.
Step 3: Size Your Solar Panels
A simple rule of thumb: you want enough solar to replace what you use in about 4–5 peak sun hours per day. If you use 150Wh daily, you need at least 30–40W of solar — but in reality, cloud cover, shade, and panel angles mean you want 2–3x your daily usage in solar wattage.
Most van roofs fit 200–400W of panels comfortably. For a 150Wh daily user, 200W of solar is plenty. For heavy users running air conditioning or large fridges, 400W+ is worth it.
Panel types: Rigid monocrystalline panels are the most efficient and cost-effective for van roofs. Flexible panels are tempting but degrade faster when bonded flat to a roof without airflow. Use rigid panels on a tilt mount or with a slight air gap if possible.
Step 4: Choose a Charge Controller
Your charge controller sits between your solar panels and your battery. There are two types:
- PWM (Pulse Width Modulation): Cheaper, simpler, less efficient. Fine for small systems under 200W.
- MPPT (Maximum Power Point Tracking): 20–30% more efficient, handles higher voltages, worth the price for any system 200W+.
For most builds, a Victron SmartSolar MPPT is the gold standard. The 100/20 handles up to 280W of panels and connects to your phone via Bluetooth. It's not the cheapest option, but Victron's build quality and support are genuinely excellent.
Step 5: Add a Battery-to-Battery Charger (DC-DC Charger)
Solar alone won't cut it on cloudy weeks or during heavy winter travel. A DC-DC charger (also called a B2B charger) pulls power from your alternator while you drive and tops up your leisure battery safely — without stressing your van's starter battery.
The Renogy 40A DC-DC charger is a popular mid-range option. Victron makes an excellent Orion-Tr Smart if you want the full Victron ecosystem.
Wiring It All Together
Always use correctly-rated cable, install a fuse on every positive wire within 18 inches of the battery, and use a bus bar to keep your wiring tidy. Under-rated wiring is the #1 cause of van electrical fires — don't cheap out on cable thickness or fuses.
A typical wiring order: Panels → Charge Controller → Battery → Bus Bar → Loads (fridge, lighting, inverter, etc.)
Recommended Starter Kit
For a first-time builder doing a modest setup (fridge + lights + device charging):
- 2x 100W rigid monocrystalline panels
- Victron SmartSolar MPPT 100/20
- 100Ah LiFePO4 battery (BougeRV, Renogy, or Battle Born)
- Renogy 40A DC-DC charger
- 500W pure sine inverter for occasional AC devices
Total cost for this setup: roughly $800–1,200 depending on brand choices. It will comfortably handle most van lifers' needs and is easily expandable later.