What Size Solar Panel for a Caravan?
Author: Steve Fairless
Originally Published: 28th April 2024 · Updated: 28th August 2026
For a caravan, there is no single “correct” solar-panel wattage. A 100 W panel can be useful for battery maintenance and light electrical demand, 200–300 W is a more realistic starting range for regular off-grid use with a compressor fridge and device charging, and 400 W or more may be appropriate for higher daily energy use. The right figure comes from your daily watt-hours, seasonal sunlight, leisure-battery capacity, controller limits and available roof or portable-panel space.
Most of our work at Sustainable Energy Engineering is fixed solar PV for homes and businesses, but the electrical sizing principles are the same: measure the load first, then size generation, storage and power electronics as one system. For a caravan, that also means allowing for 12 V equipment, travel vibration, cable length, roof penetrations, weight, portable deployment and the very large difference between summer and winter solar yield.
This guide is designed to help you calculate a sensible starting point before buying hardware. Caravan electrical systems vary, so any work involving the vehicle's mains hookup, charger, inverter, lithium battery integration or fixed wiring should be checked against the equipment manufacturer's instructions and, where appropriate, completed by a competent leisure-vehicle electrical specialist.
Updated: 28th August 2026 with current leisure-vehicle solar guidance and current MPPT controller specifications.
Caravan Solar Panel Size: Quick Guide
- 40–80 W: mainly battery maintenance, alarms and very light intermittent 12 V demand.
- 100–150 W: useful for light touring demand, LED lighting, pumps and charging small devices, especially in summer.
- 200–300 W: a stronger starting point for regular off-grid touring with a compressor fridge and several daily loads.
- 400 W+: can suit high off-grid demand, larger lithium batteries, heavier inverter use or longer stays away from hookup.
- Winter: size expectations down, not up. UK winter daylight and solar elevation can reduce available energy dramatically even with a large panel.
These are planning ranges, not guarantees. Calculate your own daily watt-hours before choosing a panel.
Start With Energy, Not Panel Wattage
The most common sizing mistake is starting with a product label — “100 W kit”, “200 W kit”, “400 W kit” — before calculating what the caravan actually uses. Panel power is measured in watts. Daily electrical demand is better measured in watt-hours.
If a 20 W device runs for five hours, it consumes 100 Wh. If a 5 W light runs for four hours, it uses 20 Wh. Add every significant load together to create a daily energy budget.
A Worked Caravan Energy Example
The table below is an illustrative touring day, not a universal appliance specification. Actual fridges, pumps, TVs, routers and chargers vary considerably, and thermostatically controlled appliances do not run at full rated power continuously.
| Load | Assumed use | Daily energy |
|---|---|---|
| Compressor fridge | 40 W average while running, equivalent to 8 full-load hours | 320 Wh |
| LED lighting | 10 W for 4 hours | 40 Wh |
| Phones / USB devices | Combined charging allowance | 60 Wh |
| Water pump | 60 W for 0.5 hour equivalent | 30 Wh |
| Laptop / tablet | 60 W for 2 hours | 120 Wh |
| Total | 570 Wh/day |
Turn Daily Watt-Hours Into a Solar Array Size
A simple planning calculation divides daily energy by the equivalent full-sun hours available and then allows for real system losses.
Using the 570 Wh/day example, 3 equivalent peak-sun-hours and a 0.75 overall planning factor:
That points toward roughly a 300 W array rather than a 100 W panel if the aim is to replace that day's energy under those assumed conditions. The system factor is there because real panels do not spend all day at nameplate power and there are losses in temperature, angle, cabling, the charge controller and battery charging.
Why “Hours of Sunshine” Is Not the Same as Peak-Sun-Hours
A summer day can have many hours of daylight without the panel producing its rated output for all of them. Nameplate watts are measured under standard test conditions. Morning and evening irradiance is lower, cloud reduces irradiance, a horizontal caravan roof is not always at the ideal angle and panel temperature can reduce output.
That is why sizing from “10 hours of daylight × 200 W = 2 kWh” usually overstates real production.
What Industry Guidance Says About 100 W Caravan Panels
The Caravan and Motorhome Club's current technical guidance says that, as a reference point, at least a 40 W panel is needed simply to keep a caravan or motorhome battery topped up while on-site, with additional electrical devices increasing the demand. For actual off-grid touring, that maintenance figure should not be confused with the array size needed to replace a full day's consumption; our sizing ranges therefore start from the loads and daily watt-hours rather than from a single generic panel size.
100 W Is a Useful Benchmark, Not a Universal Answer
A 100 W panel can be excellent for maintaining a leisure battery and extending off-grid time, but it cannot guarantee 100 W continuously. In poor weather it may contribute a fraction of that rating, while in good summer conditions it can make a very meaningful contribution to daily 12 V use.
How Battery Size Changes the Solar Requirement
A solar panel replaces energy; the leisure battery stores it. If the battery is very small, a large array can reach the battery's charge limit quickly. If the battery is large but the array is too small, the battery may progressively discharge over several days.
| Battery label | Approximate nominal energy | Important qualification |
|---|---|---|
| 12 V, 100 Ah | About 1,200 Wh using nominal 12 V | Actual battery voltage, usable depth of discharge and chemistry change the usable figure. |
| 12.8 V, 100 Ah lithium | About 1,280 Wh nominal | Usable capacity depends on the battery management system and manufacturer limits. |
| 24 V, 100 Ah | About 2,400 Wh nominal | Higher system voltage does not create energy; it changes current for a given power. |
We recommend using the manufacturer's stated usable energy where available rather than assuming every 100 Ah battery can safely deliver the same percentage of its nominal capacity.
MPPT Charge Controller Sizing Matters as Much as the Panel
The solar panel does not normally connect straight to a leisure battery. A charge controller regulates the electrical transfer and applies the charging profile required by the battery. MPPT controllers can operate the panel at a higher-voltage maximum-power point while converting the output to the lower battery-charging voltage.
Victron's current SmartSolar specifications show how controller limits interact with array size. The SmartSolar MPPT 75/15, for example, is rated for a maximum 15 A battery charge current and a nominal PV power of 220 W on a 12 V battery. The MPPT 100/20 is rated at 20 A and a nominal 290 W of PV on 12 V. Both list peak conversion efficiency of 98%.
Do Not Size a Controller From Panel Watts Alone
Check maximum PV open-circuit voltage, short-circuit current, battery voltage, maximum charge current and the controller manufacturer's permitted array power. Open-circuit voltage rises in cold conditions, so series-connected panels need a cold-voltage check rather than a simple room-temperature total.
What Does a 230 V Inverter Do to Your Energy Budget?
A caravan's solar and leisure battery are DC systems. A 230 V inverter converts battery DC into mains-style AC for compatible appliances. The inverter itself introduces losses, and high-power appliances can draw very large DC current from a 12 V battery.
The Camping and Caravanning Club gives a useful example: to supply a 100 W AC load through an inverter, around 120 W — roughly 10 A from a 12 V battery — may be required once conversion losses are allowed for.
This is why kettles, hairdryers, electric heaters and cooking appliances change the calculation so dramatically. A 2,000 W appliance at roughly 12 V represents well over 150 A before losses. That is an entirely different electrical system from a few LED lights and USB chargers.
Fixed Roof Panel or Portable Solar Panel?
Fixed Roof Solar
- Generates whenever the roof has light.
- No daily setup.
- Useful while driving or parked.
- Roof vents and aerials can create shade.
- Usually lies close to horizontal, reducing winter optimisation.
Portable / Folding Solar
- Can be moved into sun while the caravan is parked in shade.
- Can be tilted and re-aimed during the day.
- Requires setup, storage and secure cabling.
- Must be protected against theft, wind and accidental damage.
- Controller and connector compatibility still need checking.
Rigid vs Flexible Panels on a Caravan
Rigid framed panels are generally well ventilated and mechanically robust when mounted correctly, but they add height and require secure brackets. Flexible panels can follow roof curvature and reduce height, but installation quality and heat dissipation become especially important because the module may sit close to the roof surface.
Rather than assuming one is always better, look at the roof material, curvature, mounting method, available ventilation, manufacturer instructions and how the panel will be replaced if it eventually fails.
Shade Is More Important on a Caravan Than Many People Expect
A roof-mounted panel can be shaded by a satellite dish, TV aerial, rooflight, air-conditioning unit or nearby tree. Because caravans are intentionally parked in pleasant places, the best pitch for living comfort can be a poor pitch for solar generation.
Portable panels solve some of that problem because they can be placed outside the shade. Fixed solar is more convenient, so many higher-use systems combine both approaches.
How Much Solar for Different Touring Styles?
| Touring style | Planning range | Typical design priority |
|---|---|---|
| Storage / battery maintenance | 20–80 W | Offset alarm, tracker and natural battery self-discharge; winter output is the limiting condition. |
| Light summer touring | 100–150 W | Lighting, pumps and device charging with conservative battery use. |
| Regular off-grid use | 200–300 W | More dependable daily recovery with a compressor fridge and electronics. |
| Heavy off-grid electrical use | 400–600 W+ | Larger battery bank, higher loads and longer stays away from hookup; roof area and controller size become major constraints. |
These ranges are deliberately broad because location, month and lifestyle matter more than a generic wattage label.
Summer and Winter Need Different Expectations
A caravan system that feels oversized in June can feel small in November. Winter brings shorter days, lower solar elevation and more frequent cloud. If your touring is mainly spring and summer, it may be reasonable to size around those months. If you need year-round off-grid power, the system needs much more conservative assumptions and often another charging source.
What We Would Measure Before Choosing the Panel
Caravan Solar Sizing Checklist
- List every 12 V and 230 V load.
- Record watts or amps and realistic daily run-time.
- Convert everything to daily Wh.
- Decide which month and location the system must work in.
- Measure usable fixed roof area around vents and obstructions.
- Decide whether portable solar can supplement the roof.
- Check leisure-battery chemistry, capacity and usable energy.
- Check MPPT input voltage, current and charge-current limits.
- Allow for cable length and voltage drop at 12 V.
- Confirm fusing, isolation and cable protection.
- Review payload and roof-mount loading.
- Plan a second charging route if year-round off-grid use is essential.
Why a Home Solar Calculation Is Different From a Caravan Calculation
A grid-connected house can import electricity whenever solar output is low. A caravan operating off-grid cannot. That means a caravan system is usually sized around energy autonomy and battery state of charge, while a home system is more often optimised around annual generation, self-consumption, export and grid economics.
If you are comparing the two because you are also considering fixed solar at home, our home solar PV and solar battery storage pages explain how those grid-connected systems are designed.
A Practical Starting Point for Caravan Solar
If your caravan use is light and mainly in summer, 100–150 W can be genuinely useful. If you want reliable off-grid operation with a compressor fridge, device charging and several daily loads, 200–300 W is often a more realistic starting conversation. If you expect regular inverter use or long periods without hookup, calculate the daily energy first because 400 W or more may be justified.
The panel is only one part of the answer. A balanced system has enough battery capacity, an appropriately sized MPPT controller, suitable cable and protection, realistic seasonal assumptions and a charging plan for days when the weather does not cooperate.
