Camper, mobile office, workshop, or mobile business — tell us your use case and trailer size. Because your roof is flat, you can fit more rigid solar than a van of the same length, and we'll show you exactly how much.
Six quick steps. Each answer feeds directly into your panel count, battery size, inverter rating, and — if you tow — your DC-DC charger recommendation.
This sets your default appliance list and typical power tier — you can adjust everything in Step 4.
Determines your usable flat roof space and the maximum rigid solar array that will physically fit.
Cargo trailers have no engine of their own — this changes how you top up the battery.
Toggle everything you plan to run. List is pre-filtered for your use case — add or remove anything.
This sets your battery autonomy target and how much your DC-DC charger contributes.
Sets your peak sun hours — the number your solar sizing actually runs on.
Select a state to see your average daily peak sun hours.
| Factor | Cargo Trailer | Van |
|---|---|---|
| Roof type | Flat ✅ | Curved |
| Panel type needed | Rigid ✅ | Flexible |
| Typical panel efficiency | 20–22% ✅ | 15–18% |
| Panel cost per watt | $0.80–1.20 ✅ | $1.50–2.50 |
| DC-DC charging | Dedicated B2B charger | Direct from alternator |
| Weight capacity | Higher ✅ | Lower |
* Estimates assume a 12V LiFePO4 system, ~25% wiring and inverter losses, and your selected state's average peak sun hours. Treat this as a starting point — a licensed electrician should sign off on your final build.
Most first-time builders assume a van is the better solar platform because it's the popular build. It isn't — not for solar. The reason comes down to one word: flat.
A flat roof accepts standard rigid panels. A curved van roof forces you into flexible panels, which run 15–18% efficiency versus 20–22% for rigid, cost roughly $1.50–2.50 per watt versus $0.80–1.20, and typically last 5–10 years instead of 25.
Take a 7×16 ft footprint. Your cargo trailer's flat roof fits five 200W rigid panels — 1,000W. A Ford Transit of similar length fits three flexible 200W panels at best — 600W. That's 66% more solar in the same footprint, on panels that last two and a half times longer.
The one place vans still win: you drive where you live. For everything solar-related, the flat-roof cargo trailer wins by a wide margin.
| Trailer | Roof Area | Rigid Panels | Max Solar |
|---|---|---|---|
| 5×8 | 40 sq ft | 2 × 200W | 400W |
| 6×12 | 72 sq ft | 3 × 200W | 600W |
| 7×14 | 98 sq ft | 4 × 200W | 800W |
| 7×16 | 112 sq ft | 5 × 200W | 1,000W |
| 8×20 | 160 sq ft | 6 × 200W | 1,200W |
| 8×24 | 192 sq ft | 8 × 200W | 1,600W |
Your trailer has no engine, so charging from your tow vehicle needs a different approach than a van.
7-pin trailer connector → battery
Dedicated DC-DC (B2B) charger → battery
| Commute | 7-Pin (Wrong) | DC-DC Charger (Right) |
|---|---|---|
| 30-minute drive | ~5–7Ah | ~20Ah |
| 45-minute drive | ~7–11Ah | ~30–37Ah |
| 2-hour drive | ~20–30Ah | ~40–80Ah |
Recommended: Renogy DCC50S (~$120) is the most common choice for cargo trailer conversions — a simple two-wire run from your tow vehicle's battery to your trailer's battery. Expect payback inside a year through reduced solar panel requirements alone.
An air compressor's starting surge can be 2–3× its running wattage. Undersizing your inverter for this is the single most common mobile workshop mistake.
Best baseline setup: 800W solar + 200Ah battery + 3,000W pure sine inverter handles roughly 80% of workshop needs. Keep a generator on hand for the compressor specifically rather than sizing your whole solar system around it.
Contractors weren't the only ones to discover enclosed trailers — beauty and personal-care businesses are converting them into mobile studios too. The power math looks different from a camper.
| Load | Watts |
|---|---|
| Hair dryer | 1,875W |
| Flat iron | 1,000W |
| Salon lighting | 100W |
| AC (client comfort) | 1,200W |
| POS + music system | 60W |
| Peak load, all running | 4,235W |
A 1,875W hair dryer used 4 hours a day needs roughly 7,500Wh — that alone calls for a 2,000W+ solar system if you want to cover it on solar.
Solar's honest role here: lighting, POS, and music are easy wins. A hair dryer and AC unit are not — solar alone usually isn't enough.
Hybrid approach (recommended): 600W solar + 100Ah battery covers lighting, POS, and breaks between clients. A small quiet generator (2,200W) handles the hair dryer and AC on demand — running only during services, for a quieter client experience and lower fuel cost than sizing solar for peak load.