What Can a 200W, 300W or 400W Solar Panel Run in a Van?
By Frank Zale · July 14, 2026 · 5 min read
Solar panels are sold by watts, but you live in watt-hours. A 200W panel makes roughly 750 Wh on a decent day — enough for a fridge, fan, lights, and phones. A 300W panel makes about 1,100 Wh — add a laptop and a diesel heater. A 400W array makes about 1,500 Wh — add Starlink and light cooking. Here's exactly how those numbers break down.
How much energy each size really makes
A panel almost never produces its sticker rating. Heat, wiring losses, charge inefficiency, and imperfect sun angle typically cost about 25%. The honest formula:
Daily Wh ≈ panel watts × peak sun hours × 0.75
At 5 peak sun hours (a reasonable US average — check your region on our location pages):
| Array size | Daily output (5 PSH) | Winter output (2.5 PSH) |
|---|---|---|
| 100W | ~375 Wh | ~190 Wh |
| 200W | ~750 Wh | ~375 Wh |
| 300W | ~1,125 Wh | ~560 Wh |
| 400W | ~1,500 Wh | ~750 Wh |
| 600W | ~2,250 Wh | ~1,125 Wh |
Note the winter column — it's half. If you camp year-round, size for the season you'll actually be out in. The how much solar guide covers seasonal sizing in depth.
What can a 200W solar panel run?
About 750 Wh per day buys you the essentials:
| Appliance | Wh/day |
|---|---|
| 12V compressor fridge | ~420 |
| Roof vent fan (6h) | 150 |
| LED lights (4h) | 60 |
| Phone charging | 30 |
| Total | ~660 Wh |
That's a classic weekender setup with a little margin. What 200W will not support: daily laptop work, Starlink, or any electric cooking. Cloudy stretches will also outrun it — pair it with at least a 100Ah battery for a one-day buffer.
What can a 300W solar panel run?
About 1,125 Wh per day — the essentials plus real work:
| Appliance | Wh/day |
|---|---|
| Everything in the 200W list | ~660 |
| Laptop (4h charging) | ~290 |
| Diesel heater (4h average) | 120 |
| Total | ~1,070 Wh |
300W is the sweet spot for part-timers who work from the van a few days at a time. It fits on almost any van roof, and it pairs naturally with a 200Ah battery — see 100Ah vs 200Ah for why the battery matters as much as the panel.
What can a 400W solar panel run?
About 1,500 Wh per day — full-time territory:
| Appliance | Wh/day |
|---|---|
| Everything in the 300W list | ~1,070 |
| Starlink (8h) | 400 |
| Total | ~1,470 Wh |
At 400W you're running a remote-work setup indefinitely in decent sun. Add an electric kettle or induction burner used sparingly and you'll want 500–600W and a 300Ah+ bank — electric cooking is the single biggest jump in van power budgets. Check what your inverter needs to handle with the inverter sizing tool.
What no reasonable van array can run
Be skeptical of anyone selling "air conditioning on solar" for a standard van roof:
- Air conditioning: a small 12V AC pulls 400–1,000W for hours. That's 3,000+ Wh per afternoon — more than a 600W array makes all day.
- Electric space heaters: 1,500W for hours. Use a diesel heater instead (30W average).
- Full-size residential fridges: 100–200W cycling constantly. Use a 12V compressor fridge.
Rooftop solar is superb at running efficient DC loads and electronics. It is terrible at making heat or moving serious BTUs.
Panels are only half the system
A panel with no battery does nothing at night, and a big battery with a small panel never refills. The two must be sized together, along with the charge controller and wire:
- Add up your daily watt-hours (appliance list × hours).
- Solar: daily Wh ÷ (PSH × 0.75).
- Battery: daily Wh × 2 days ÷ 1,024 per 100Ah LiFePO4 — details in the amp-hours guide.
- Controller and wiring: follow the array — the MPPT sizing page shows how.
Or skip the arithmetic: the free van solar calculator takes your appliance list and returns the full parts list — panels, battery, controller, wire, fuses, and cost estimate — in about two minutes.
FAQ
Will a 200W solar panel run a 12V fridge?
Yes, comfortably in decent sun. A compressor fridge uses ~420 Wh/day; a 200W panel makes ~750 Wh/day at 5 sun hours. Cloudy days are covered by the battery, not the panel — carry at least 100Ah.
Is 400W of solar enough for full-time van life?
For a fridge, fan, lights, laptop, Starlink, and a diesel heater — yes, in most US sun. Add electric cooking or winter travel in the Pacific Northwest and you'll want 600W or a DC-DC alternator charger as backup.
How many solar panels fit on a van roof?
A Sprinter 144 fits roughly 400–500W alongside a fan and vents; a Sprinter 170 or Transit high-roof fits 600W+. Panel dimensions matter more than watts — measure before you buy.
Do I need 24V panels for a 12V system?
Panel voltage doesn't need to match battery voltage when you use an MPPT controller — it converts the difference into charging current. Higher-voltage panels actually charge earlier in weak light.