Most campervans need between 150W and 400W of solar, but the correct amount depends on how much electricity you use, when you travel and how often the battery is also charged while driving or on mains hook-up.

A small campervan used for summer weekends may manage comfortably with 100–150W. A vehicle running a compressor fridge, diesel heater, laptops and other equipment while spending several days off-grid may need 300–500W or more.

The panel wattage alone does not answer the question.

You also need to consider:

• Daily electrical consumption
• Leisure-battery capacity
• Available roof space
• Summer or winter use
• Solar-panel shading
• Charging while driving
• Access to mains hook-up
• How long the vehicle remains parked
• The type of solar controller fitted

At WeConvert, we design and install campervan and motorhome solar systems from our Blackburn workshop, matching the panel capacity, battery bank and charging equipment to how the vehicle will actually be used.

Quick Campervan Solar Sizing Guide

These are starting points rather than fixed recommendations.

A well-designed 200W system may outperform a poorly positioned 400W installation affected by shade, unsuitable wiring or an incorrectly configured controller.

Solar Panels Do Not Produce Their Rated Wattage All Day

A solar panel’s advertised wattage is its maximum rated output under controlled test conditions.

A 200W panel does not normally produce:

200W × 24 hours = 4,800Wh per day

It produces power only while sufficient daylight is available, and its real output is affected by:

• Cloud
• Sun angle
• Season
• Shade
• Panel temperature
• Dirt
• Wiring losses
• Controller efficiency
• Battery state of charge

A practical planning calculation is:

Daily solar energy = panel wattage × equivalent full-sun hours × system-efficiency allowance

For example, using a 200W solar array, four equivalent full-sun hours and a 75% planning allowance:

200W × 4 hours × 0.75 = 600Wh per day

That does not mean the system produces 200W continuously for four hours. It means the changing output across the day is approximately equivalent to four hours at full rated power.

Actual production can be significantly higher or lower.

Example solar-yield estimates

The following figures illustrate how changing daylight conditions affect the same installation.

These examples use a 75% allowance for real-world losses and should not be treated as guaranteed daily output.

The key lesson is that season and weather can matter as much as panel size.

Start With Your Daily Electrical Consumption

The best way to size a campervan solar system is to estimate how much electricity the vehicle uses during a normal day.

For each appliance, identify:

1. Its power consumption
2. How many hours it operates
3. Whether it runs continuously or cycles
4. Whether it is powered directly from 12V or through an inverter

A basic calculation is:

Watt-hours used = appliance wattage × hours used

For equipment rated in amps:

Wattage = voltage × current

A 12V appliance drawing 4A uses approximately:

12V × 4A = 48W

If it operates for five hours:

48W × 5 hours = 240Wh

Typical campervan electrical-use examples

These are broad planning ranges. Actual consumption must be checked from the equipment fitted.

The fridge is often one of the largest continuous loads in a campervan, but a large inverter left switched on can also use substantial energy without powering an obvious appliance.

Read Why Does My Campervan or Motorhome Leisure Battery Keep Going Flat Overnight? for a detailed guide to normal consumption, hidden drains and battery faults.

Example 1: Light Summer Weekend Use

A small campervan is used mainly between April and September.

Daily equipment includes:

• LED lights: 40Wh
• Water pump: 15Wh
• Phone charging: 30Wh
• Small ventilation fan: 50Wh
• Control equipment: 25Wh

Estimated total:

160Wh per day

A 100W solar panel producing around 300Wh on a reasonably bright day could replace this consumption.

However, the owner should still allow for:

• Cloudy days
• Partial shading
• Battery inefficiency
• Vehicle parked indoors
• Additional unplanned loads

A practical system could be:

• 100–150W solar
• MPPT charge controller
• 100Ah leisure battery
• Alternator charging as a backup

This may be enough for occasional summer use without a compressor fridge.

Example 2: Typical Touring Campervan

The vehicle uses:

• Compressor fridge: 450Wh
• Lighting: 60Wh
• Water pump: 20Wh
• Phones and tablet: 70Wh
• Control systems: 40Wh
• Occasional diesel-heater use: 100Wh

Estimated total:

740Wh per day

A 200W array may provide enough energy during good summer conditions, especially where the vehicle is also driven regularly.

However, in dull weather, 200W may replace only part of the daily consumption.

A more resilient setup could be:

• 250–300W solar
• MPPT controller
• 150–230Ah lithium battery
• DC-to-DC charging while driving
• Battery monitor

This does not guarantee unlimited off-grid use, but it provides a better balance between daily consumption, battery capacity and charging opportunities.

Example 3: Remote Working and Longer Off-Grid Stays

The vehicle uses:

• Compressor fridge: 500Wh
• Laptop: 250Wh
• Monitor or additional electronics: 150Wh
• Router: 100Wh
• Lighting: 60Wh
• Phones: 40Wh
• Water pump: 20Wh
• Diesel heater: 200Wh
• Inverter losses and standby: 120Wh

Estimated total:

1,440Wh per day

A 300W panel array is unlikely to replace this amount consistently in typical UK conditions.

A suitable system might require:

• 400–600W solar
• Large MPPT controller
• 300Ah or larger lithium bank
• Strong alternator charging
• Mains charger
• Careful inverter management
• Detailed roof-layout planning

Even then, several dark winter days can create an energy deficit.

The practical solution may include a combination of solar, driving and occasional mains hook-up rather than relying on solar alone.

Is 100W of Solar Enough for a Campervan?

A 100W panel can be enough for light electrical use during brighter months.

It may support:

• LED lights
• Water pump
• Phone charging
• Basic control equipment
• Small occasional loads

It is less likely to support a compressor fridge continuously throughout mixed UK weather without help from alternator or mains charging.

A 100W panel may also be useful as:

• A maintenance charger
• Supplement to driving
• Upgrade for an occasional-use vehicle
• Solution where roof space is limited

It should not be presented as a complete off-grid solution for every campervan.

Is 200W of Solar Enough?

A 200W system is a common starting point for campervans running:

• Compressor fridge
• Lighting
• Water pump
• Phone charging
• Diesel-heater controls
• Modest electronics

During strong summer conditions, it may replace a large proportion of normal daily use.

During cloudy weather or winter, it may produce much less than the vehicle consumes.

A 200W array works best where:

• The van is driven regularly
• The roof has minimal shade
• High-power inverter use is limited
• Battery capacity is sensible
• The owner monitors daily energy use

For many touring campervans, 200–300W provides a more useful balance than a single small panel.

Is 300W of Solar Enough?

A 300W array can support a more demanding setup involving:

• Compressor fridge
• Diesel heater
• Laptop use
• Television
• Device charging
• Longer off-grid stays

It can produce useful daily energy in spring and summer but should not be assumed to cover all consumption throughout winter.

A 300W installation may be a good choice for owners who want stronger off-grid capability without filling the entire roof with panels.

The design still needs to consider:

• Rooflights
• Vents
• Aerials
• Awning rails
• Pop-top movement
• Cable routes
• Controller capacity

When Would You Need 400W or More?

A larger array may be suitable where the vehicle has:

• Large lithium battery bank
• Remote-working equipment
• Frequent inverter use
• High daily fridge consumption
• Long periods parked off-grid
• Limited driving
• Several occupants
• Greater winter use

It may also provide better recovery after a day of poor weather.

However, 500W of solar does not automatically create a high-power electrical system.

A large solar array still needs:

• Suitable battery capacity
• Correct controller
• Adequate cable
• Appropriate fuses
• Safe roof mounting
• Enough roof area
• Realistic energy management

A vehicle using 2,000Wh per day can still develop an energy deficit if its solar array produces only 800Wh in poor weather.

Why Winter Solar Is More Difficult

Campervan solar production usually falls in winter because of:

• Shorter days
• Lower sun angle
• More cloud
• Greater shading
• Panels remaining flat
• Increased heater use
• Longer periods using lights
• Reduced battery performance in cold conditions

This is particularly relevant in Blackburn and across Lancashire, where winter touring can involve long periods of grey weather.

A solar system that performs well during July may struggle to replace the same electrical use during December.

For genuine winter off-grid use, consider:

• Greater solar capacity
• Strong DC-to-DC charging
• Efficient appliances
• Larger battery bank
• Reduced inverter use
• Occasional mains charging
• Monitoring daily consumption

Solar should be treated as one part of the charging system rather than the only source.

Flat Campervan Panels Versus Tilted Solar Panels

Most campervan and motorhome panels are mounted flat because the vehicle:

• Travels in different directions
• Needs a low roof profile
• Cannot be repositioned constantly
• Must withstand driving conditions

A flat panel is convenient, but it rarely faces the sun at the ideal angle.

A tilting system can improve performance when parked correctly, particularly during low-sun conditions. However, it introduces additional considerations:

• Wind loading
• Roof access
• Locking mechanism
• Safe travel position
• Manual adjustment
• Vehicle orientation
• Added height

Portable panels can also be positioned towards the sun, but they require:

• Storage
• External cable
• Security
• Manual setup
• Weather protection
• Suitable controller connection

For most owners, a larger permanently fixed flat array is more convenient than repeatedly tilting or moving panels.

Shading Can Reduce Solar Output Significantly

Solar-panel placement is as important as panel wattage.

Campervan roofs often contain:

• Rooflights
• Pop-top roofs
• Ventilation fans
• Aerials
• Satellite equipment
• Roof bars
• Awning brackets
• Cable glands

These can cast shadows across a panel.

The effect depends on:

• Panel construction
• Bypass diodes
• Wiring arrangement
• Whether panels are in series or parallel
• Location of the shade
• Time of day

A rooflight may cast little shade at midday but cover part of the panel during the morning and afternoon.

Before choosing panel sizes, the complete roof layout should be assessed.

Leaving a small gap between roof furniture and the panel can sometimes provide better output than squeezing in a slightly larger panel that remains shaded.

Rigid or Flexible Solar Panels?

Rigid solar panels

Rigid framed panels are commonly used because they can provide:

• Airflow beneath the panel
• Strong structure
• Replaceable mounting arrangements
• Good long-term performance
• Easier inspection

They add more height and must be attached using suitable brackets and fixings.

Flexible solar panels

Flexible panels can offer:

• Lower profile
• Reduced weight
• Installation on some curved surfaces
• Less visible roof equipment

Potential disadvantages include:

• Greater heat build-up when fully bonded
• Difficult removal
• Roof-surface dependence
• Greater sensitivity to movement
• Hidden water or adhesion problems
• Shorter lifespan in some installations

The decision should be based on the roof, available space, panel construction and intended lifespan rather than appearance alone.

How Much Battery Capacity Should You Have?

Solar panels generate energy. The leisure battery stores it.

A useful system needs enough battery capacity to cover:

• Overnight use
• Poor weather
• Periods when the vehicle is shaded
• Higher-than-normal consumption
• Time before the next drive or hook-up

A 300W solar array paired with a very small battery may waste available solar once the battery is full.

A large 400Ah battery paired with only 100W of solar may take a long time to recharge.

The system should be balanced.

Typical planning combinations might include:

These are not compatibility rules.

Battery chemistry, daily use, charging current and required reserve all affect the correct design.

For lithium pricing and supporting charger requirements, read How Much Does a Campervan or Motorhome Lithium Battery Upgrade Cost?.

A Larger Battery Does Not Create More Energy

Increasing battery capacity gives you more stored energy, but it does not solve an energy shortage by itself.

For example:

• Daily use: 1,000Wh
• Solar generation: 500Wh
• Daily deficit: 500Wh

A larger battery allows the vehicle to continue for longer before becoming flat, but the system still loses 500Wh each day.

The long-term solution requires one or more of the following:

• More solar
• More driving
• Stronger alternator charging
• Mains charging
• Lower consumption
• More efficient appliances

Battery capacity and charging capacity must be considered together.

MPPT or PWM Solar Controller?

The charge controller manages the power moving from the panel into the leisure battery.

PWM controller

A PWM controller can be suitable for small, basic systems where panel and battery voltages are closely matched.

Advantages can include:

• Lower cost
• Simple operation
• Small physical size

MPPT controller

An MPPT controller can operate the panel at a more effective voltage and convert the available power into a suitable battery-charging output.

It is generally preferred for:

• Larger solar arrays
• Higher-voltage panels
• Series-connected panels
• Mixed weather
• Limited roof space
• Systems where maximising yield matters

The controller must be sized for:

• Maximum panel open-circuit voltage
• Maximum input current
• Expected charge current
• Battery voltage
• Panel configuration
• Low-temperature voltage changes

Adding more panels without checking the controller’s limits can damage equipment or cause charging faults.

Series or Parallel Solar Panels?

Multiple panels can be connected in series or parallel.

Series connection

Series wiring increases voltage while current remains broadly similar.

Possible benefits include:

• Lower current through the roof cable
• Reduced cable losses
• Easier cable sizing
• Earlier controller startup in some conditions

Possible disadvantage:

• Shading one panel can affect the wider series string

Parallel connection

Parallel wiring increases current while voltage remains broadly similar.

Possible benefits include:

• One shaded panel may have less effect on the others
• Panels can operate more independently

Possible disadvantages include:

• Higher cable current
• Larger cables or additional protection
• More roof connectors

The correct arrangement depends on the panels, controller, roof shading and cable route.

It should not be chosen solely from a generic diagram.

Can Solar Charge While You Are Driving?

Yes.

The solar controller can normally continue charging while the alternator or DC-to-DC charger is also operating, provided the system has been designed and configured correctly.

Modern charging equipment generally adjusts its output according to battery voltage and state.

Multiple charging sources may include:

• Solar
• DC-to-DC charger
• Mains charger
• Inverter-charger

Each must use settings suitable for the battery.

If the battery is not charging from any source, read Why Is My Campervan Leisure Battery Not Charging?.

Do Solar Panels Work When the Battery Is Full?

Yes, but the controller will normally reduce its charging output once the battery reaches the required charging stage.

This can make a healthy system appear to be underperforming.

For example:

• Panel capacity: 300W
• Battery: nearly full
• Active electrical load: 40W

The controller may produce only enough energy to maintain the battery and support the current load.

It does not need to force the full 300W into a full battery.

Where the solar controller shows little or no output, check whether the battery is already charged before assuming that the panel has failed.

For fault diagnosis, read Campervan or Motorhome Solar Panel Not Charging the Battery?.

Can Solar Power an Inverter?

Solar panels do not usually power an inverter directly.

The normal energy route is:

Solar panel → charge controller → leisure battery → inverter → 230V appliance

The battery supplies the inverter’s immediate demand while the solar system replaces some of the energy.

A 2,000W appliance may draw over 2,000W from the battery after inverter losses, even where only 400W of solar is available.

Solar can reduce the net battery discharge, but it cannot make a small system capable of running unlimited high-power appliances.

The battery, BMS, inverter, cables and fuses must all support the load.

Can You Have Too Much Solar?

More solar is generally helpful, but there are practical limits.

Potential constraints include:

• Available roof area
• Controller voltage rating
• Controller current rating
• Cable size
• Panel weight
• Mounting strength
• Shading
• Rooflight access
• Pop-top operation
• Battery charge-current limit
• Budget

An oversized panel array may also spend much of the summer restricted because the battery is already full.

That does not make it harmful where correctly designed, but the extra cost should be weighed against how often the additional capacity will be useful.

Common Campervan Solar-Sizing Mistakes

Choosing solar from battery size alone

A 200Ah battery does not automatically require a particular panel wattage.

The correct calculation begins with energy consumption and charging opportunities.

Ignoring winter use

A system sized only from summer expectations may struggle during colder months.

Forgetting inverter standby consumption

A large inverter can use energy even when no obvious appliance is operating.

Fitting panels where they are shaded

A larger shaded panel can perform worse than a smaller panel with a clear view of the sky.

Adding panels without checking the controller

The new array may exceed the controller’s permitted voltage or current.

Assuming the panel rating equals daily generation

Panel wattage is peak power, not guaranteed daily energy.

Adding a large battery but no additional charging

The battery takes longer to become flat but also takes longer to recharge.

Ignoring other charging sources

A vehicle driven most days may need less solar than one parked for a week.

How We Size a Campervan Solar System

At our Blackburn workshop, solar-system planning may include:

1. Listing the equipment you use
2. Estimating realistic daily consumption
3. Reviewing summer and winter use
4. Checking the existing leisure battery
5. Identifying existing alternator and mains charging
6. Measuring available roof space
7. Assessing rooflight and pop-top shading
8. Checking panel and controller compatibility
9. Calculating cable and fuse requirements
10. Considering future upgrades
11. Explaining the likely limitations during poor weather
12. Providing an installation specification and quotation

We do not recommend a solar-panel wattage based solely on the size of the vehicle.

Two identical campervans can need very different systems depending on how their owners use them.

Campervan and Motorhome Solar Installation in Blackburn

WeConvert provides campervan and motorhome solar installation, upgrades and fault finding from our Blackburn workshop.

We can help with:

• New solar-panel installations
• Additional solar capacity
• Rigid and flexible panel assessment
• MPPT charge controllers
• Lithium-compatible charging
• Solar cable entries
• Roof-layout planning
• Battery monitors and shunts
• Leisure-battery upgrades
• DC-to-DC chargers
• Off-grid electrical systems
• Existing self-build installations
• Solar faults and low output

Our Blackburn workshop serves customers travelling from:

• Blackburn
• Darwen
• Accrington
• Burnley
• Rossendale
• Bolton
• Chorley
• Preston
• Wider Lancashire

Learn more about our campervan electrical and solar services in Blackburn.

Where the current system is not operating correctly, also see:

• Campervan or Motorhome Solar Panel Not Charging the Battery?
• Why Does My Leisure Battery Keep Going Flat Overnight?
• Why Is My Campervan Leisure Battery Not Charging?
• Campervan or Motorhome 12V Electrics Not Working?
• Campervan and Motorhome Repairs and Fault Finding

Frequently Asked Questions

How many watts of solar does a campervan need?

A typical campervan may need between 150W and 400W.

Light summer use may require less. Longer off-grid stays, winter touring, laptops and large lithium systems may require 400–600W or more.

Is 100W of solar enough for a campervan fridge?

It may support part or all of the fridge’s consumption in strong summer conditions, but it may not do so consistently in cloudy UK weather.

The fridge consumption, battery capacity and other charging sources must also be considered.

Is 200W of solar enough for a campervan?

For many touring campervans, 200W can make a meaningful contribution to a compressor fridge, lights, pump and device charging.

It may still require alternator or mains charging during poor weather.

Is 300W of solar enough for off-grid camping?

It can support moderate off-grid use, especially during spring and summer.

The result depends on daily consumption, shade, season and how many days the vehicle remains parked.

How much solar do I need for a 200Ah battery?

The answer depends on how much energy you remove from the battery each day.

A 200Ah battery paired with 200–400W of solar is common, but the correct capacity should be calculated from usage and charging opportunities.

How much solar do I need for a compressor fridge?

Many compressor fridges use approximately 300–600Wh per day, depending on their size, ventilation and operating conditions.

A 150–250W array may support the fridge during favourable conditions, but additional loads and poor weather must be included.

Can I run a diesel heater from solar?

The heater runs from the leisure battery.

Solar can replace some or all of the electricity used by the heater, depending on the panel capacity, weather and other loads.

Will a larger solar panel charge the battery faster?

It can, provided there is sufficient sunlight and the battery, controller and wiring can accept the additional current.

When the battery is nearly full, the controller will reduce the charging rate.

Do campervan solar panels work in winter?

Yes, but daily output is usually lower because of shorter days, lower sun angles and cloudier weather.

Winter electrical planning should include alternator or mains charging as a backup.

Can I add another solar panel to my existing system?

Possibly.

The new panel must be compatible with the existing array, controller voltage and current limits, wiring and roof layout.

Can WeConvert upgrade a solar system fitted by another converter?

Yes, subject to inspection and access.

We can assess professionally converted, factory-built and self-build campervan or motorhome systems at our Blackburn workshop.

Book a Campervan Solar Assessment in Blackburn

To discuss a new solar installation or upgrade, send us:

• Vehicle make, model and year
• Campervan or motorhome type
• Photograph of the complete roof
• Existing solar-panel capacity
• Solar-controller make and model
• Leisure-battery type and capacity
• DC-to-DC charger details
• Mains charger details
• Inverter size
• Appliances you use
• Typical time spent off-grid
• Whether you travel during winter
• Your postcode

We can then recommend an appropriate starting specification and identify whether any existing equipment can be retained.

Contact WeConvert to request campervan or motorhome solar installation in Blackburn.