Learning Zone · Practical guide 2026
Solar panels for campers: sizing a kit, battery and charge controller
From daily energy needs to panel watts: a simple guide with tables, calculations and a complete 200 Wp example for campervans and motorhomes.
What does a camper solar panel actually do?
It keeps the leisure battery charged while parked and supports 12 V loads without immediately starting the engine or finding shore power. It does not create endless autonomy: output depends on sun, season, shade, battery and habits.
Correct sizing starts with daily watt-hours, not with an arbitrary panel wattage.
1. Build a daily energy budget
Multiply each appliance’s power by its hours of use. For 12 V loads, amps × volts × hours gives watt-hours.
On a smartphone, swipe the table horizontally to see every column.
| Example load | Power | Daily use | Energy |
|---|---|---|---|
| LED lights | 18 W | 4 h | 72 Wh |
| Efficient 12 V fridge, indicative average | 45 W | 10 equivalent h | 450 Wh |
| Water pump | 50 W | 0.3 h | 15 Wh |
| Phones and USB | 25 W | 2 h | 50 Wh |
| Fan and electronics | 30 W | 3 h | 90 Wh |
| Example total | 677 Wh/day |
Add 15–25% for conversion, standby and variation. The example design target is about 800 Wh/day.
2. How much does a 200 W solar panel generate?
Multiply Wp by equivalent peak-sun hours and system efficiency. A camper roof is rarely ideally oriented and roof lights, aerials or racks can cast shade.
On a smartphone, swipe the table horizontally to see every column.
| Equivalent sun | Theoretical output | Estimated useful energy |
|---|---|---|
| 2 h | 400 Wh | 300–320 Wh |
| 3 h | 600 Wh | 450–480 Wh |
| 4 h | 800 Wh | 600–640 Wh |
| 5 h | 1,000 Wh | 750–800 Wh |
| 6 h | 1,200 Wh | 900–960 Wh |
Estimate at 75–80% overall efficiency, not a guarantee. Heat, shade and a nearly full battery reduce harvested energy.
3. Components and their purpose
On a smartphone, swipe the table horizontally to see every column.
| Component | Purpose | Practical choice |
|---|---|---|
| Rigid panel | Durable and usually well ventilated. | Good when roof and payload accept mounts. |
| Flexible panel | Low weight and follows curves. | Needs correct support and thermal design. |
| MPPT controller | Matches voltage and maximises harvest. | Size voltage, current and battery profile. |
| Leisure battery | Stores energy. | AGM or lithium with compatible charging. |
| Cables and fuses | Carry and protect current. | Correct section, length and source-side protection. |
| Gland and mounts | Seal and secure equipment. | Match roof, wind load and waterproofing. |
Rigid or flexible panel?
Rigid panels are often easier for durability and cooling but add height and weight. Flexible panels reduce weight and profile, while installation must avoid overheating, water traps and excessive bending.
4. How much battery capacity?
At 12 V, 1,000 Wh is theoretically about 83 Ah. Usable capacity depends on chemistry and discharge limits; never assume the full nameplate capacity.
On a smartphone, swipe the table horizontally to see every column.
| Battery example | Nominal energy | Prudent usable estimate | Note |
|---|---|---|---|
| 12 V 100 Ah AGM | 1.20 kWh | About 0.60 kWh | Avoiding deep discharge helps life. |
| 12.8 V 100 Ah LiFePO₄ | 1.28 kWh | About 1.00–1.15 kWh | Requires BMS and matching charge profile. |
| Two 100 Ah batteries | Double nominal | Depends on wiring | Cables and protection must be balanced. |
A 230 V appliance also requires an off-grid inverter sized for continuous and surge power, with extra losses.
5. Installation sequence and safety
- Choose a low-shade location within roof load and vehicle dimensions.
- Plan short cable routes away from abrasion and heat.
- Mount and seal supports and cable gland with roof-compatible products.
- Install isolation and fuses; normally connect battery to controller before the panel, following the manual.
- Select the battery profile, verify polarity and voltage, then test charging.
Complete example: 200 Wp PRO Dual Battery camper kit
The MR WATT CAMP200-P includes a 200 Wp polycrystalline panel (124 × 99 × 4 cm), controller for leisure and starter batteries, remote display, 20 m of PV cable, mounts, adhesive, connectors and waterproof gland. Four peak-sun hours equal 800 Wh theoretical, about 600–640 Wh after typical losses. Battery, inverter, fuses, isolators and battery power cables are not included.
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Pre-purchase checklist
- Add Wh/day for summer, winter and weekend use.
- Measure clear roof area, payload and shade.
- Choose battery and desired autonomy before the controller.
- Check panel cold-weather Voc and maximum current.
- Size cables, fuses, isolators and inverter correctly.
- Treat alternator and shore power as complementary winter sources.
Camper solar panel FAQ
Is 200 W enough for a camper?
It can cover lights, electronics, pump and an efficient fridge in good conditions. Winter or high-power inverter loads may need more or another charging source.
How many amp-hours can 200 W produce?
With four peak-sun hours and losses, 600–640 Wh is roughly 45–50 Ah around 12–13 V. Actual output varies.
MPPT or PWM?
A correctly sized MPPT can better use voltage headroom and variable conditions. The gain depends on system design.
Can a panel connect straight to the battery?
No. Use a compatible solar charge controller and suitable protection.
Does it charge the starter battery too?
Only when the controller has a second output or dedicated management. CAMP200-P is a Dual Battery kit.