Campervan Solar Setup: The Definitive UK Guide (2025)

Solar power is what makes genuine off-grid van life possible. Park in a field for a week, face your panels at the sky, and your batteries replenish passively while you do whatever you drove there to do.

In the UK, solar is also where many new van builders get their expectations wrong. Panels that produce 400W in full Mediterranean sun produce much less on a grey November morning in Yorkshire. Understanding how UK solar output actually behaves — by season, by location, by cloud cover — is the difference between a solar system that works for you and one that constantly disappoints.

This guide covers everything: panel selection, UK output data, charge controller sizing, wiring configurations, mounting, and troubleshooting. For how solar fits into your overall system, see our campervan electrical system guide.

How Solar Panels Work (The Essentials)

A solar panel is an array of photovoltaic cells. When photons strike the cells, they excite electrons and generate a DC voltage and current. The power produced (watts) = voltage × current.

In a campervan context:

• A "12V" panel typically produces 18–21V open-circuit voltage (Voc) in full sun. The MPPT controller manages this down to the appropriate battery charging voltage.
• Rated wattage (e.g., "200W") is measured under Standard Test Conditions (STC): 1,000W/m² irradiance, 25°C cell temperature, AM1.5 spectrum. These conditions don't exist in the UK in winter (or often in summer).
• Real-world output is typically 70–85% of STC rating under good UK summer conditions.

UK Solar Output: The Real Numbers

The single most important data point for solar sizing in the UK is peak sun hours — the number of equivalent full-intensity sun hours per day, averaged over the location and month.

UK Peak Sun Hours by Month and Region

Source: Based on PVGIS dataset for representative UK locations.

What this means in practice:

A 300W solar array in South England produces:

• January: 300W × 0.7h × 0.85 efficiency = 179Wh per day
• June: 300W × 5.0h × 0.85 efficiency = 1,275Wh per day
• April (shoulder season): 300W × 3.7h × 0.85 = 944Wh per day

If your daily consumption is 1,000Wh, that 300W array comfortably covers you in summer, marginally meets needs in April, and falls well short in winter. This is the case for most UK van builds — solar alone isn't enough for a winter liveaboard without supplementing with DC-DC charging or shore power.

Seasonal Planning

Spring to Autumn (March–October): A well-sized solar array can sustain most van builds without additional charging. Peak sun hours of 2.5–5.0 in this period provide ample generation from 300–400W of panels.

November–February: Solar alone is insufficient for most builds. Plan around DC-DC charging (driving daily or long drives every few days) and shore power at campsites. Size your battery bank with 2+ days of autonomy to bridge between charging sessions.

Cloud Cover Effect

The UK's famously overcast weather doesn't kill solar output entirely. On a fully overcast day, panels produce approximately 10–25% of their rated output. On a partly cloudy day, 30–60%. Only dense, continuous cloud cover reduces output severely.

The peak sun hour figures above already account for average UK cloud cover — they're observed figures, not theoretical clear-sky calculations. Your actual output will vary day to day, but over a month the average will track the table above fairly closely.

Temperature Effect on Panel Output

Solar panels are more efficient at lower temperatures. The STC rating (25°C) is actually higher than typical UK operating temperatures, which means UK panels often outperform their STC rating on cool clear spring days. Don't worry about this — it's a positive.

In hot summer conditions (panel surface temperature of 60°C+, which can occur on dark van roofs in direct sun), output drops by 10–15%. This is most pronounced for panels mounted flush to a dark roof surface without air gap underneath.

Choosing Solar Panels

Rigid vs Flexible: The Key Decision

Rigid monocrystalline panels (aluminium frame, glass front, 3–5cm deep) are the standard choice for campervan roof installations:

• Efficiency: 20–23% (best available for the size)
• Lifespan: 25+ years with ~0.5% annual output degradation
• Cost: £0.50–£0.80 per watt at common sizes (100W–200W)
• Require mounting brackets (adds 10–30mm additional height)
• Cannot conform to curved surfaces
• Best heat management: air gap under panel keeps temperature lower, preserving efficiency

Flexible monocrystalline panels (thin film on flexible backing, 3–5mm deep):

• Efficiency: 18–21% (lower than rigid due to thinner cells and no AR coating)
• Lifespan: 5–10 years typical (the flexible substrate degrades over time, especially from UV and flexing)
• Cost: £0.80–£1.50 per watt — more expensive per watt for lower performance
• Can be adhered directly to curved or flat roof surfaces
• No brackets needed — lower profile, no wind noise
• Poor heat management: adhesive mounting creates a thermal sandwich between panel and roof, raising cell temperature and reducing output

The verdict:

For a permanent van build, rigid panels are the better technical choice in almost every case. The weight difference is small (rigid panels weigh 8–12kg per 200W; flexible 3–5kg), and the efficiency, longevity, and cost advantages of rigid panels outweigh the profile advantage of flexible.

The case for flexible panels:

• Your van has a significantly curved roof (some VW Transporters) where rigid panels won't sit flat
• You're doing a stealth build where low profile is critical
• You have a short-term van build and don't need 25-year longevity

For a VW Transporter with a steeply curved roof, flexible panels may be the only option that lies flat without a custom mounting frame. For a Transit or Sprinter with a near-flat roof, rigid panels are better in every measurable way.

Panel Efficiency: Why It Matters for Vans

A higher-efficiency panel produces more watts per square metre. On a van with limited roof area, this matters.

If you have 2.5m² of usable roof space:

• Standard mono rigid: 2.5 × 200 = 500W maximum
• Premium mono (Sunpower): 2.5 × 225 = 562W maximum
• Standard flexible: 2.5 × 195 = 487W maximum

The difference in total possible array size is modest. Premium panels like Sunpower Maxeon cost significantly more per watt; for most builds, standard monocrystalline rigid panels are the correct choice.

Popular Panel Brands in the UK

Victron Energy solar panels: Well-built, reliable, but expensive per watt (~£1.50/W). The ecosystem integration with Victron MPPT controllers is seamless. Good choice for full Victron ecosystem builds.

Renogy: The most popular budget-to-mid-range option. Good quality cells at competitive prices (~£0.60–£0.80/W for standard mono). The Renogy 200W Monocrystalline Rigid is a staple of UK van builds.

Rich Solar / ECO-WORTHY: Budget options, more variable quality control. Acceptable for budget builds; inspect carefully on arrival.

Bimble Solar (UK retailer): UK-based supplier of panels, MPPT controllers, and mounting equipment. Good for sourcing a complete solar kit with matching components.

For specific panel recommendations with performance data, see best solar panels for campervans.

Portable vs Roof-Mounted

Portable solar panels on a folding stand can be angled toward the sun and positioned away from shade. They're a genuine advantage for output — a portable panel angled to face the sun directly produces 30–50% more power than a fixed horizontal panel.

The downsides:

• Must be deployed manually and stowed when driving
• Vulnerable to theft if left out unattended
• Require an external cable connection to the van
• Not practical in rain

Best use case for portable: A van that parks long-term in one location, where you can position the panels optimally and don't need to pack up daily. Many van lifers carry one portable panel to supplement roof-mounted panels when parked in a fixed spot.

The MPPT Charge Controller

The MPPT (Maximum Power Point Tracking) charge controller is the brain of the solar system. It sits between the panels and battery, continuously adjusting the electrical load it presents to the panels to extract maximum power, then regulating its output to correctly charge the battery.

MPPT vs PWM: The Choice You Must Get Right

PWM (Pulse Width Modulation) controllers are simple, cheap, and largely obsolete for campervan use. They work by rapidly switching the connection between panels and battery, essentially dragging the panel voltage down to the battery voltage.

The problem: a typical 12V panel produces 18V at its maximum power point (Vmp). A 12V battery being charged sits at 13–14.5V. A PWM controller drags the panel voltage down to ~14V, throwing away the power difference between 18V and 14V — wasting approximately 20–25% of available panel output.

MPPT controllers continuously track the panel's maximum power point — the voltage/current combination that produces maximum watts — and convert that to whatever voltage the battery needs. An MPPT controller working with an 18V Vmp panel charging a 14V battery is 95–99% efficient, capturing nearly all available panel output.

The math:

200W array with PWM controller (25% loss): 200W × 0.75 × 4 peak sun hours = 600Wh/day

200W array with MPPT controller (5% loss): 200W × 0.95 × 4 peak sun hours = 760Wh/day

The MPPT produces 27% more energy from the same panels. This is the difference between meeting your daily budget and falling short.

Use MPPT for all campervan builds. PWM is only technically appropriate for systems under 80W with a perfectly matched panel-to-battery voltage ratio (e.g., a 17.5V Vmp panel charging a 14.4V battery) — conditions that rarely occur in practice.

Sizing Your MPPT Controller

The MPPT controller must be sized correctly on both input (solar array) and output (battery) sides.

Output side: The controller's output current rating (in amps) must exceed the maximum current it will deliver to the battery.

MPPT output current = Solar array wattage ÷ Battery voltage

Example: 300W array, 12V battery: = 300W ÷ 12V = 25A output → needs a 30A controller

Example: 400W array, 12V battery: = 400W ÷ 12V = 33.3A → needs a 40A controller

Input side (voltage): The controller's maximum input voltage (Vmax) must exceed the maximum open-circuit voltage (Voc) of the panel array. Check the panel spec sheet for Voc. Add 20% safety margin for cold temperatures (panel Voc increases in cold weather).

In series wiring (see below), Voc of the array = Voc of one panel × number of panels in series.

Input side (wattage): The controller's rated wattage determines the maximum panel capacity you can connect. A Victron SmartSolar MPPT 100/30 is rated for up to 440W at 12V (the "100" refers to 100V maximum input; the "30" refers to 30A output).

Victron SmartSolar MPPT Controllers

The most popular choice for UK van builds:

For most builds:

• 100–300W array: SmartSolar 75/15 or 100/20
• 300–440W array: SmartSolar 100/30
• 440–700W array: SmartSolar 100/50
• 700W+ array: SmartSolar 150/60

The Bluetooth connectivity in the "Smart" range allows monitoring and configuration via the Victron Connect app. All SmartSolar controllers support VE.Smart Networking (sharing temperature and voltage data with other Victron devices via Bluetooth).

Configuration: What to Set in the Controller

After installation, configure the controller for your battery chemistry via Victron Connect:

For LiFePO4:

• Absorption voltage: 14.2–14.4V
• Float voltage: 13.5V (or disabled)
• Equalisation: Off
• Low temperature cutoff (if battery temp sensor connected): 5°C

For AGM:

• Absorption voltage: 14.4–14.7V
• Float voltage: 13.6–13.8V
• Equalisation voltage: 14.8V (occasional, disabled for most leisure use)

Tail current: The current level at which the controller transitions from absorption to float, indicating the battery is full. For LiFePO4: set to 4% of battery capacity (e.g., 8A for 200Ah). For AGM: 2–4%.

Series vs Parallel Panel Wiring

How you wire multiple panels together affects voltage, current, and shade resilience.

Series Wiring

Panels wired in series: positive terminal of panel 1 → negative terminal of panel 2, etc. Total voltage adds; current stays the same.

Two 100W panels (Voc: 22V, Isc: 5.8A) in series:

• Array Voc: 44V
• Array Isc: 5.8A
• Array power: 44V × 5.8A = ~200W

Advantage: Higher voltage allows thinner cable over long runs (less current = less voltage drop = thinner cable). Useful for long cable runs from roof to controller (over 5m).

Disadvantage: One shaded panel reduces the output of the entire string significantly. If a roof vent or antenna shades one panel, both panels underperform.

Parallel Wiring

Panels wired in parallel: positive to positive, negative to negative. Voltage stays the same; current adds.

Two 100W panels (Voc: 22V, Isc: 5.8A) in parallel:

• Array Voc: 22V
• Array Isc: 11.6A
• Array power: 22V × 11.6A = ~200W

Advantage: Shade-resilient. One shaded panel reduces its own output without pulling down the others. Better for vans with partial shading from roof accessories.

Disadvantage: Higher current requires thicker cable over long runs.

Practical Recommendation for UK Vans

For two panels on a typical Transit/Sprinter roof:

• If cable runs are short (under 4m): Wire in parallel. Better shade tolerance. Use 6mm² cable.
• If cable runs are long (over 4m): Wire in series to keep current lower. Use 4mm² cable. Ensure your MPPT controller's maximum input voltage exceeds the series Voc with a 20% cold weather margin.

Example: Two panels with 22V Voc each in series = 44V array. The Victron SmartSolar 75/15 (75V max input) handles this safely. In cold conditions, Voc increases to approximately 26V per panel = 52V — still within 75V limit.

For three or more panels: the choice becomes more nuanced. See solar panels series vs parallel — campervan for the full analysis with three-panel and four-panel configurations.

Mounting Solar Panels

Roof Rack vs Direct Mount

Roof bars/rack mounting: The most robust method. Steel or aluminium roof bars span the width of the van; panels are clamped to the bars. This allows:

• Air gap under the panels (better cooling, 5–10% better output than flush-mounted)
• Easy angle adjustment (tilt mounts available for roof bar systems)
• Removal of panels if needed

Downside: increases van height by 5–15cm (check underground car parks and ferry deck height limits). Some roof bar systems add significant weight (steel bars can add 10–20kg).

Flush direct mounting: Panels mounted with low-profile Z-brackets or tilt feet bolted directly to the van roof. Lower profile, lighter, but:

• Requires drilling the roof (must be properly sealed)
• Panels closer to the roof surface (warmer = slightly lower output)
• Fixed position — can't adjust angle or remove panels easily

Adhesive mounting: Flexible panels (or rigid panels with special mounting pads) bonded directly to the roof with adhesive. No roof penetration, lowest profile, but:

• Very poor heat dissipation (panels overheat on summer days)
• Removal is destructive — the adhesive bonds permanently
• Not suitable for rigid panels (they expand and contract; adhesive can't absorb the movement)

Roof Penetrations: Getting Them Waterproof

Cables from roof-mounted panels must enter the van interior through a sealed penetration. Done poorly, this is a water ingress point that causes corrosion and mould.

Options:

Purpose-made cable entry glands: Plastic or aluminium housings designed to mount flush to the roof and pass cables through with rubber seals. The Bimble Solar cable gland, Soprasolar entry plates, and similar products are installed by cutting a hole in the roof, inserting the gland, and bedding with butyl tape or sikaflex sealant. Allow 2+ MC4 cables.

Grommet through the roof: Simple rubber grommet in a drilled hole. Works, but less neat than a purpose gland and the hole must be carefully sealed with suitable sealant (Sikaflex 252 is the standard for van roof penetrations).

Through the side via a vent: Some builders route cables down the outside of the van and through a side vent or window seal rather than through the roof. Avoids a roof penetration but adds cable length.

Best practice regardless of method:

• Form a "drip loop" in the exterior cable — route the cable downward before it enters the penetration, so any water running down the cable drips off the loop rather than following the cable inside
• Use Sikaflex 252 or similar flex sealant (not silicone — silicone degrades in UV and eventually cracks)
• Cover the penetration fitting with the lid or weatherproof cover if it comes with one
• Test before you drive in rain: park in rain or pour water over the roof

See solar cable routing through van roof for the step-by-step guide.

Tilt Mounting for Extra Output

Roof-mounted panels face the sky at whatever angle the roof sits — near-horizontal on most vans. Solar panels produce maximum output when perpendicular to the sun. In the UK, the sun's maximum elevation angle ranges from ~16° (winter) to ~62° (summer solstice) at around 52°N.

A tiltable mount lets you angle panels toward the sun when parked. Output gains:

In winter — when solar is already scarce — tilting panels can dramatically change your charging balance. A 300W array producing 180Wh/day flat-mounted might produce 270Wh/day at optimal winter tilt.

The downside: tilt mounts add height (significant if you use a ferry or park in height-restricted areas), and you must manually adjust the tilt angle and ensure it's stowed before driving.

Cable Sizing for the Solar System

Between panels (series or parallel runs): Use MC4 compatible cable — typically 4mm² or 6mm² solar cable. This is UV-resistant, double-insulated cable designed for exterior solar use. Don't use standard automotive cable outdoors.

From array to MPPT controller:

Long cable runs in series arrays (higher voltage, lower current) allow smaller cable — advantage of series wiring for long roof-to-controller runs.

From MPPT controller to battery:

This carries the MPPT output current. Size to the MPPT output rating:

Fusing: Fuse the cable between MPPT output and bus bar within 300mm of the bus bar connection. A 30A controller needs a 40A fuse on this cable.

Anderson connectors: Many builders use Anderson SB50 connectors at the roof penetration — this allows the roof section of cabling to be disconnected from the interior section, useful if you ever need to remove the roof cables.

Maximising Solar Output: Practical Tips

Orientation: Park facing south (in the UK) when stationary to maximise exposure. A van facing north loses 30–50% of potential solar output compared to south-facing. On campsites, try to choose a south-facing pitch.

Shade avoidance: Even partial shading of one panel significantly reduces output. Trees, buildings, and roof accessories (MaxxAir fans, roof bars, antennas) can all cause shading. When planning panel placement, consider what will shade the roof at different times of day.

Clean panels: Dirty panels lose output — dust, bird droppings, and grime accumulate. A clean with soapy water when you wash the van keeps output up.

Temperature management: In summer, ensure the highest-power panels have adequate airflow underneath. Panels mounted on roof bars with a 50–100mm air gap run cooler and more efficiently than panels adhesively bonded to the roof.

Battery acceptance: MPPT controllers can only push current into the battery at a rate the battery will accept. A LiFePO4 battery in bulk charge accepts current up to its BMS limit (often 100A for a 200Ah battery). A battery approaching full (absorption phase) progressively accepts less current — which is correct behaviour. If you see the MPPT "derate" on a sunny day when the battery is nearly full, this is normal.

Check shade-induced losses: Use the Victron Connect app's history to see daily maximum power generated. If peak power is consistently well below array rated output on sunny days, there may be shading you haven't noticed.

Troubleshooting Your Solar System

No output from the MPPT controller:

1. Check panel open-circuit voltage at the MPPT input — should be above battery voltage and positive relative to the correct polarity. If reading 0V, check panel connections and MC4 connectors.

2. Check MPPT output voltage — should equal or exceed battery voltage. If panel input is correct but output is 0, the controller may have a fault or incorrect settings.

3. Verify the MPPT is configured for the correct battery chemistry and voltage. A 24V-configured MPPT connected to a 12V battery won't charge correctly.

Output much lower than expected:

1. Check for shade on any panel — even small shadows disproportionately reduce output (especially in series-wired arrays).

2. Check Voc at the panels — if significantly below spec, a panel may be faulty (cell cracking from physical damage).

3. Check cable connections — loose MC4 connectors have higher resistance, reducing current flow.

4. Check the MPPT app for "maximum power today" — if much lower than theoretical (array watts × peak sun hours × 0.85), there's a system issue.

MPPT output lower than expected in cold weather:

Cold temperature can cause panel Voc to exceed the MPPT's Vmax limit, at which point the MPPT protects itself by reducing input. Check the panel's Voc at 0°C from the spec sheet and ensure it's below the MPPT's Vmax with the safety margin included. If not, reconfigure to parallel wiring to reduce string voltage.

Inverter interfering with MPPT:

Large inverter loads on the battery bus bar can cause voltage fluctuations that confuse the MPPT's tracking algorithm, causing it to momentarily reduce output. This is usually minor and self-correcting. If severe, check battery cable sizing — excessive voltage drop under load may look like a battery voltage fluctuation to the MPPT.

Related Guides

• Campervan battery guide — sizing the battery your solar charges
• Campervan charging systems guide — DC-DC and shore power to complement solar
• Campervan wiring & safety guide — cable sizing for solar circuits
• Campervan inverters guide — using your solar-charged battery for mains power
• Campervan electrical system guide — the full picture

FAQ

How many solar panels can I fit on a campervan?

Depends on the van model. A long-wheelbase, high-roof Sprinter or Transit has approximately 3.5–4.5m² of usable roof area — enough for 600–800W of rigid panels (allowing for HVAC vents, roof rack rails, etc.). A VW Transporter or short-wheelbase Transit typically accommodates 200–300W. See your specific van's roof dimensions and subtract space for roof accessories.

Do solar panels work in the UK?

Yes, with realistic expectations. Summer output can be excellent — nearly matching southern European output in a good June. Winter output is severely limited (0.4–0.8 peak sun hours in December). A UK van build must treat solar as the primary source in summer and a supplementary source in winter, with DC-DC charging and occasionally shore power as the backbone through the darker months.

Can I install solar panels myself?

Absolutely. Solar panel installation is one of the more accessible parts of a van build. The main challenge is the roof penetration — getting cables from the roof to the interior in a genuinely waterproof way. The wiring and controller installation are straightforward if you follow cable sizing rules.

What's the minimum solar setup worth having?

A 100W panel with a Victron SmartSolar 75/15 MPPT controller costs approximately £130–£180 in components. At 3 UK summer peak sun hours, this produces 255Wh/day — enough to run a compressor fridge (around 1,000Wh/day, so it covers ~25%) and charge phones. It's a worthwhile starting point, but most full-time van builds need 300W+ for viable self-sufficiency.

Should I get a solar controller with Bluetooth?

Yes. The Victron SmartSolar Bluetooth controllers are only marginally more expensive than non-Bluetooth versions, and the data they provide — daily energy production, charging history, current state — is invaluable for monitoring system performance and diagnosing problems. The VE.Smart networking (sharing data with other Victron Bluetooth devices) is also useful.

Why does my MPPT output less than the panel's rated wattage?

Multiple reasons: the STC rating is a lab measurement at 1,000W/m² and 25°C — rarely achieved in UK conditions. Panel efficiency losses, partial shading, high temperature, and cable losses all reduce real-world output below the nameplate figure. Expect 70–85% of STC in ideal conditions, and plan around seasonal output figures rather than the panel's nameplate watts.

Can I run solar and a generator simultaneously?

Yes. The solar MPPT controller and the mains charger (powered by the generator) are both connected to the battery bus bar and can charge simultaneously. The MPPT won't conflict with the mains charger — both regulate their output voltage independently.