Solar panels can keep a campervan leisure battery topped up without a hook-up, but the right system depends on your daily energy use, roof space and when you travel. For most UK vans, the sensible approach is to calculate your energy demand first, fit the largest practical array that stays within the charge controller’s limits, and keep an alternative charging source for dark winter days.
This guide explains how to choose, size and wire solar panels for a campervan. It covers rigid and flexible panels, series and parallel connections, MPPT controller checks, safe installation and realistic UK performance.
Quick answer: which solar panel is best for a campervan?
A rigid monocrystalline panel is usually the best all-round choice where the roof and payload allow it. Rigid panels are durable, can be mounted with an air gap for cooling and generally offer good output from limited roof space. Semi-flexible panels are lighter and lower-profile, but their service life and temperature performance depend heavily on panel quality and how they are mounted.
Do not choose a panel by wattage alone. Check all five points:
- your daily energy use in watt-hours (Wh);
- the usable roof area after allowing for vents, roof lights and shading;
- the panel array’s voltage and current limits;
- the solar charge controller’s input and output ratings; and
- the battery’s permitted charging voltage and current.
Do you need solar panels on a campervan?
Solar is useful if your van spends time parked away from mains hook-up. It can replace some of the energy used by a fridge, lighting, water pump, phones, laptops and other 12V equipment. It also works silently and automatically while there is enough daylight.
Solar is less useful when the roof is often shaded, the van is stored indoors, or most trips take place during the UK winter. In those cases, alternator charging through a suitable DC-DC charger or a mains battery charger may contribute more energy.
Solar does not create unlimited power. A large inverter load, electric cooking or space heating can consume more energy than a campervan roof can realistically replace. Start with an energy budget before buying panels.
How to size solar panels for a campervan
1. Calculate daily energy use
For each appliance, multiply its power in watts by the hours it runs each day:
Daily energy (Wh) = power (W) × running time (hours)
For equipment that cycles, such as a compressor fridge, use a realistic average from the manufacturer’s data or measured consumption rather than multiplying its maximum power by 24 hours. Add every item to find the total daily energy demand.
| Example load | Power | Daily use | Energy |
|---|---|---|---|
| LED lights | 18W | 4 hours | 72Wh |
| Laptop charger | 60W | 2 hours | 120Wh |
| Phones and small devices | 15W | 3 hours | 45Wh |
This example totals 237Wh before adding the fridge, pump, heater fan or inverter losses. Your own measured figures are more useful than a generic “typical van” estimate.
2. Allow for sunlight and system losses
A panel only produces its rated power under standard test conditions. Real output changes with cloud, shade, panel angle, temperature, dirt, cable losses and controller efficiency. A useful planning formula is:
Required panel watts = daily Wh ÷ expected peak-sun hours ÷ system factor
A system factor is an allowance for real-world losses. Use reliable solar-yield data for the places and months in which you travel, and test more than one scenario. A system sized for summer touring may be far too small for December. If roof space cannot support the calculated array, reduce demand or plan another charging source rather than assuming the solar will catch up.
3. Check the battery can accept the charge
The battery bank must use the correct charging profile and accept the controller’s possible output current. Follow the battery manufacturer’s limits, especially for lithium batteries with a battery management system. Battery capacity alone does not prove that any controller size is suitable.
Rigid or flexible solar panels?
| Panel type | Advantages | Limitations | Best fit |
|---|---|---|---|
| Rigid framed | Robust construction, air gap supports cooling, easy to replace on brackets | Heavier, taller and needs secure mounting | Most permanent campervan installations |
| Semi-flexible | Low profile, light and can suit gently curved surfaces | Heat and poor bonding can shorten life; removal may be difficult | Weight- or height-sensitive builds using a proven mounting method |
| Portable or folding | Can be moved into sunlight and stored when not needed | Needs setup, storage and theft protection | Occasional use or vans with little clear roof space |
Monocrystalline describes the cell technology; rigid and flexible describe the panel construction. These are not competing labels. You can buy monocrystalline cells in both rigid and semi-flexible panels.
Series or parallel wiring?
With two or more compatible panels, the wiring arrangement changes the array voltage and current.
- Series: voltages add while current stays broadly the same. Higher voltage can reduce cable losses and help an MPPT controller begin charging in weaker light, but one shaded panel can restrict the whole series string.
- Parallel: currents add while voltage stays broadly the same. Independent branches can cope better with uneven shade, but the higher current may require larger cable and additional branch protection.
Do not choose solely on a rule such as “series for cloud” or “parallel for shade”. First calculate the array’s maximum open-circuit voltage (Voc), short-circuit current (Isc) and operating current. Then compare them with the controller limits under the coldest expected conditions. Panel voltage rises as cell temperature falls, so a string that appears acceptable from the label value can exceed a controller’s input limit on a cold bright morning.
Use electrically compatible panels in the same string. Mixed panels can force the array away from each panel’s best operating point and reduce output.
How to choose the solar charge controller
A solar charge controller sits between the panels and leisure battery. It controls charging and prevents the battery from being exposed directly to the panel voltage. An MPPT controller is normally preferred where roof space is limited or the array voltage is appreciably higher than battery voltage.
Before selecting a controller, confirm:
- Maximum PV voltage: the cold-corrected total Voc of every series string must remain below the controller’s absolute maximum.
- Maximum PV current: the array Isc must stay within the manufacturer’s input limit.
- Charge-current rating: the controller output must suit the panel power and battery voltage.
- Battery profile: the controller must provide settings approved for the battery chemistry and model.
- Installation sequence: follow the controller manual. Many systems require the battery connection to be established before the PV input.
The Victron SmartSolar MPPT manual, for example, states the relevant PV voltage, short-circuit current, cable, configuration and safety limits. Use the manual for the exact controller you install rather than copying settings from a different model.
Campervan solar installation safety
Solar panels produce voltage whenever light reaches them. Switching off the leisure battery does not make the PV cable safe. Cover the panels with an opaque material before working, isolate sources in the sequence specified by the equipment manufacturer and verify the circuit before touching conductors.
- Use UV-resistant cable, connectors and glands suitable for the voltage, current and environment.
- Protect cables from sharp metal edges, movement, heat and abrasion.
- Fit overcurrent protection and isolation where the design requires it; an isolator is not a substitute for a fuse.
- Do not disconnect plug connectors under load unless the connector is specifically rated for load breaking.
- Keep cable runs short where practical and calculate voltage drop.
- Seal roof penetrations using a system compatible with the roof material.
- Use a mounting method that can withstand wind uplift, vibration and vehicle movement.
- Check the van’s payload and roof-load limits before installation.
Incorrect mounting can damage the roof or allow a panel to detach at road speed. If you cannot confirm the structure, bonding method, cable protection or electrical ratings, use a competent installer.
Plan for shade and UK winter
A roof vent, aerial, roof rack or even a narrow shadow can reduce output significantly. Lay out the roof before buying panels and leave service access around equipment. If the van is regularly parked in shade, consider multiple MPPT inputs or a portable panel rather than building one long, shade-sensitive string.
UK winter days combine shorter daylight hours with lower sun angles and frequent cloud. A solar array that comfortably replaces daily use in summer may provide only a fraction of that energy in winter. Design the full charging system around the worst conditions you actually expect, including DC-DC charging or mains hook-up where appropriate.
Solar panel buying checklist
- Daily energy demand calculated in Wh
- Travel season and realistic solar yield considered
- Usable roof area measured, including shade and service clearances
- Panel dimensions, weight, Voc, Isc and temperature coefficient recorded
- Series/parallel layout checked against controller limits
- Controller charge current and battery profile confirmed
- Cable size, voltage drop, fusing and isolation designed
- Mounting and roof sealing approved for the vehicle
- Alternative charging planned for poor solar conditions
Frequently asked questions
How many watts of solar does a campervan need?
There is no single correct wattage. Divide your daily energy demand by the expected solar yield for your travel season, allow for system losses, and compare the result with available roof space. If the result will not fit, plan another source of charging.
Will a 100W solar panel run a campervan fridge?
It depends on the fridge’s measured daily energy use and the available sunlight. A 100W panel may replace the consumption of an efficient fridge in favourable summer conditions, but it should not be treated as a year-round guarantee.
Can I connect a solar panel directly to a leisure battery?
Normally, no. Use a compatible solar charge controller to regulate battery charging. Direct connection can expose the battery to unsuitable voltage and uncontrolled charging.
Are flexible solar panels worth it?
They can be useful when weight, height or a gently curved roof rules out a framed panel. Choose a reputable panel and follow its ventilation and mounting instructions. A rigid panel is generally the safer default for a permanent installation when space and payload allow.
Is series or parallel better for campervan solar panels?
Neither is always better. Series reduces array current and raises voltage; parallel keeps voltage lower and can limit the effect of shade on one branch. The correct choice must stay within the charge controller limits and suit the roof’s shading pattern and cable design.
Get the design right before installation
A good campervan solar system starts with an energy budget and ends with verified electrical and mechanical limits. Choose the panel after you know the load, roof layout, controller and battery—not before.
If you need help matching panels, an MPPT controller, cable protection and battery charging equipment, speak to Callidus Trade before ordering. A checked design is easier and safer to install than a collection of individually compatible parts.
