Last updated: 2026-11-03
Solar for camping trailers needs array watts equal to the trailer's daily watt-hours divided by peak sun hours and an assumed 0.75 system factor. For example, a trailer using 800 Wh per day at 5 peak sun hours needs about 213 W of panels.
The trailer is parked at a site with no power post, the fridge has run since morning and the battery monitor is falling by dinner time. Solar for camping trailers is a sizing problem before it is a shopping problem, because the panels, battery, controller and cable all follow from how many watt-hours the trailer uses in a day. This guide defines the numbers, works one example step by step and covers a cable-loss check that panel listings do not show.
What solar for camping trailers means
Solar for camping trailers means charging the trailer's battery from solar panels so its lights, fridge, pump and devices run without a mains hookup.
Solar power for camper trailers is a chain of panels, a charge controller, a battery and fused cabling, and its governing number is the trailer's daily energy use in watt-hours (Wh).
The sizing formula is array watts = daily Wh ÷ (peak sun hours × 0.75). Peak sun hours are the daily solar energy in kWh/m² restated as hours of 1 kW/m² sunlight, and they change with region and season. The 0.75 is an assumed system factor for heat, cable, controller and angle losses.
The formula holds only while the panels sit in full sun and face it for those hours. Solar panels for camping trailers mount on the roof, on a tilting rack or on the ground, and a panel in tree shade delivers only a fraction of its rating.
Worked example, step by step
A worked example for a camping trailer sizes the array, battery and controller current from one list of daily loads.
The loads below are assumed values for illustration, so replace them with the watts printed on your own appliances.
| Load | Power | Hours per day | Energy per day |
|---|---|---|---|
| Compressor fridge | 45 W | 10 h | 450 Wh |
| LED lights | 20 W | 4 h | 80 Wh |
| Water pump | 40 W | 0.5 h | 20 Wh |
| Ventilation fan | 15 W | 8 h | 120 Wh |
| Phones and laptop | 65 W | 2 h | 130 Wh |
| Total daily energy | 800 Wh | ||
- List every load and multiply watts × hours, as in the table. The total is 800 Wh per day.
- Pick peak sun hours for the region and season. This example assumes 5.
- Divide: 800 ÷ (5 × 0.75) = 213 W, then round up to a practical combination such as two 120 W panels, which is 240 W.
- Check the output: 240 × 5 × 0.75 = 900 Wh per day, which covers the 800 Wh load with 100 Wh spare.
- Size the battery: 800 Wh ÷ 12 V = 66.7 Ah per day. For two days of storage that is 133 Ah of usable capacity, so about 267 Ah of lead-acid at 50 percent usable or 133 to 167 Ah of lithium iron phosphate at 80 to 100 percent usable, both written as typical ranges.
- Size the controller: 240 W ÷ 12 V = 20 A, and a typical margin of 20 to 25 percent gives 24 to 25 A, so choose the next standard rating above that.
What most guides leave out: cable loss between a portable panel and the trailer
The cable between a portable panel and the trailer turns part of the panel's power into heat, and the loss grows with cable length and current and shrinks with cable cross-section.
Loop resistance is R = ρ × 2L ÷ A, voltage drop is I × R and power lost is I² × R. The example assumes copper resistivity ρ of 0.0172 Ω·mm²/m, a 6 m run each way (12 m of loop) and 10 A at 18 V, which is a 180 W panel.
| Cable cross-section | Loop resistance | Voltage drop at 10 A | Power lost | Share of 180 W |
|---|---|---|---|---|
| 2.5 mm² | 0.083 Ω | 0.83 V | 8.3 W | 4.6 percent |
| 4 mm² | 0.052 Ω | 0.52 V | 5.2 W | 2.9 percent |
| 6 mm² | 0.034 Ω | 0.34 V | 3.4 W | 1.9 percent |
| 10 mm² | 0.021 Ω | 0.21 V | 2.1 W | 1.1 percent |
A 6 m run of 2.5 mm² cable wastes 8.3 W, which is 4.6 percent of the panel's 180 W, while 6 mm² cuts that to 3.4 W. Loss is linear in length, so parking the panel at 3 m instead of 6 m halves it, the same gain as doubling the cable cross-section.
Higher voltage also helps because loss follows current squared. Two panels wired in series for 36 V at the same 180 W carry 5 A, and the 4 mm² loss falls from 5.2 W to 1.3 W, provided the controller accepts the higher input voltage.
Choosing hardware for this
Choosing hardware for solar power for camping trailers means matching panel format, controller current, battery capacity and cable size to the numbers from the worked example.
| Item | Number from the example | Spec to look for |
|---|---|---|
| Array | 213 W needed, 900 Wh per day from 240 W | Two 120 W panels sized to the roof or ground space |
| Controller | 20 A at 12 V, 24 to 25 A with margin | Current rating above 25 A and input voltage above the array's open-circuit voltage in cold weather |
| Battery | 66.7 Ah per day, 133 Ah usable for two days | About 267 Ah of lead-acid or 133 to 167 Ah of lithium iron phosphate at 12 V |
| Portable panel cable | 6 m each way at 10 A | 6 mm² copper for about 1.9 percent loss, or 4 mm² for 2.9 percent |
Roof panels charge while the trailer travels and need no setup, and portable solar panels for camper trailers can be moved into sun when the trailer is in shade. The guide on solar blanket vs solar suitcase camping compares two portable formats.
Diy solar for camping trailers uses the same chain, so the sizing steps above apply unchanged. Rigid panels of the kind used on houses can serve as a DIY roof array, and the guide to house solar panels for camping covers that route. Fit a fuse in each positive cable close to the battery.
The fridge is the largest steady load in the example, and the guide to solar panels for a 12 V camping fridge covers sizing for it.
The solar power for camping page is where panel and hardware requirements go once these numbers are fixed.
FAQ
How many solar panels does a camping trailer need?
A camping trailer needs array watts equal to its daily watt-hours divided by peak sun hours and 0.75. A trailer using 800 Wh per day needs 213 W at 5 peak sun hours and 356 W at 3 peak sun hours. Round up to whole panels that fit the roof or ground space.
Are portable solar panels good for camper trailers?
Portable solar panels suit camper trailers parked in shade, because the panel can sit in sun at the end of a cable. The cable sets the loss: a 6 m run of 4 mm² copper wastes about 2.9 percent of a 180 W panel at 10 A. Portable panels also add setup and stowage time at every stop.
Can I build DIY solar for a camping trailer?
DIY solar for a camping trailer is possible because the parts are the same chain as a kit: panels, controller, battery and cable. You own the sizing, fusing and wiring checks, so size each part from the daily watt-hours as in the worked example and fuse the positive cable near the battery. Have the finished wiring checked by someone qualified if you are unsure.
Next step
The next step is to write your trailer's numbers down as requirements: power, size, quantity and target market. Power is the array watts from the worked example, size is the roof or ground space and the travel height, quantity is the number of trailers or panels, and target market is where the equipment will be sold. LinkSolar is a China-based B2B supplier of custom & OEM solar panels, solar cells and mounting hardware.