How Many Solar Panels Do You Need on a Campervan? Solar Kit Sizing Guide

Updated: 23 September 2026 · EuroVan Shop

How many solar panels do you need on a campervan?

Enough watts to replace what you use on a typical day, plus a margin for cloud. Most van builds end up with one to three panels on the roof; the total wattage matters more than the number of panels.

Size your system in three steps:

1. Add up your daily energy use in watt-hours (Wh).
2. Estimate what each watt of panel gives you per day in the season you travel.
3. Check that the charge controller and battery match the result.

We do not sell panels, but we supply everything behind them. The VANPOWER kit includes a Victron SmartSolar MPPT 100/30 solar charge controller specified for 300 to 500 W of panels, alongside a LiFePO4 battery, alternator charging and mains charging.

Step 1: how much energy does your van use per day?

Multiply each appliance's power (W) by the hours it runs per day, then add them up. The fridge is usually the biggest item because it runs around the clock.

The fridge figure is the VanCool 40L's average draw; the lighting and laptop lines are example values, so replace them with the wattage on your own appliances. Using a 230 V appliance through an inverter adds its wattage plus some conversion losses.

Step 2: how much does a solar panel produce in a day?

Roughly: daily Wh ≈ panel watts × full-sun hours × about 0.75. The 0.75 is an assumption covering heat, dirt, cable and controller losses. "Full-sun hours" is the day's sunshine squeezed into hours of full rated output, and it changes enormously with season, latitude, weather and parking in shade.

These are rough, weather-dependent estimates to compare options, not guaranteed outputs. The Bluetooth history in the VictronConnect app shows your real daily yield once the system is running.

Worked example: sizing a campervan solar kit

For the 760 Wh a day above, plan roughly 300 to 400 W of panels for spring-to-autumn travel. The estimate:

• On a bright day, each watt of panel gives about 4 × 0.75 = 3 Wh.
• 760 Wh ÷ 3 ≈ 250 W just to break even on a good day.
• A margin for mixed weather takes you to about 300 to 400 W.

That range sits within what the Victron SmartSolar MPPT 100/30 accepts (up to 440 W at 12 V). The VANPOWER kit is specified for 300 to 500 W of panels; if you plan an array at the top of that range, ask our team to check it against your battery voltage.

For a lighter load, a small set-up can be enough: our VanCool 85L SVR uses roughly 40 to 50 Ah a day, which a 100 Ah lithium battery and a 150 W solar panel cover comfortably in summer. In winter, solar alone will not cover 760 Wh a day: see the section on other charging sources below.

Can you connect solar panels directly to a battery?

No. Always connect campervan solar panels through a solar charge controller. A panel's voltage is higher than the battery's and varies with the light; the controller converts it and stops charging when the battery is full, so the battery is neither overcharged nor damaged.

There are two types of controller:

• PWM: a simple switch between panel and battery, cheaper but less efficient.
• MPPT: tracks the panel's best operating point. The Victron SmartSolar MPPT 100/30 gives up to 30% more solar yield than a standard controller.

The SmartSolar MPPT 100/30 charges at up to 30 A, detects 12 V or 24 V automatically, works with lead-acid, AGM, GEL and lithium batteries, is protected against short circuit, reverse polarity and overheating, and operates from −30 °C to +60 °C. Its limit is up to 440 W of panels at 12 V, or 880 W at 24 V.

Compare the VANPOWER kits

What size leisure battery goes with your solar?

Enough to carry you through the night and a cloudy day or two. Solar only charges in daylight; the leisure battery supplies everything else.

With lithium you can use most of the capacity. Compare the chemistries in lithium leisure battery vs AGM.

Why solar alone is rarely enough all year

Because winter yield can be a small fraction of summer yield. A reliable campervan electrical system combines three sources: solar, the alternator while driving and hook-up on campsites.

• Alternator: the Victron Orion-Tr Smart 12/12-30A charges up to 30 A while the engine runs, an output of 430 W at 25 °C (360 W at 40 °C). As a rough estimate, an hour of driving can put back several hundred watt-hours when the battery accepts full current.
• Hook-up: the Victron Blue Smart IP22 12V 15A charges from a 230 V socket; with an inverter in the VANPOWER kit, its built-in 20 A charger does the job instead.

All three sources come pre-sized in the VANPOWER kit. See the campervan electrical system guide for the full picture.

Panels, roof layout and safe wiring

Choose panels that fit your roof, avoid shade and wire them to the controller's limits. A few general points:

• Rigid or flexible: rigid framed panels are sturdier; flexible panels are lighter and follow curved roofs. Check the maker's datasheet for output and warranty.
• Shade: a roof vent, rack or aerial that shades part of a panel can cut its output noticeably. Leave a gap around roof fittings.
• Controller limits: keep the array within 440 W at 12 V for the MPPT 100/30, and check the panels' voltage against the controller's datasheet.
• Protection: fit fuses and isolators between the controller and the battery. The VANPOWER kit uses three battery isolator switches (battery, solar and alternator circuits).

Cable sections and fuse ratings are given in the VANPOWER wiring diagram (with cable sections) or must be sized by a qualified person. For roof fixings and approval, check your national rules (DVLA/VCA, TÜV, RDW).

Frequently asked questions

How many watts of solar do I need for a 12V fridge?

A VanCool 40L at 25 W average uses about 600 Wh a day. On a bright day with our assumptions (4 full-sun hours, 0.75 losses), about 200 W of panels would cover that alone; add a margin for cloud and your other loads.

Do solar panels work on cloudy days?

Yes, but at a fraction of their rated output. That is why a campervan system also charges from the alternator through a DC/DC charger and from hook-up.

Can I add more panels later?

Yes, within the controller's limit: the Victron SmartSolar MPPT 100/30 takes up to 440 W of panels on a 12 V system. The VANPOWER kit's controller is specified for 300 to 500 W of panels.

What cable size do I need for my solar panels?

It depends on current and cable length. Cable sections are given in the VANPOWER wiring diagram, or have them sized by a qualified person.

Can I monitor my solar yield?

Yes. The SmartSolar MPPT 100/30 has built-in Bluetooth: the VictronConnect app shows live output, settings and daily history.

Does the MPPT 100/30 work with a lithium battery?

Yes. It supports lead-acid, AGM, GEL and lithium batteries, selectable in the VictronConnect app.

Related guides

• Lithium leisure battery vs AGM: is LiFePO4 worth it?
• Campervan electrical system: the complete guide
• How long will a 12V fridge run on a leisure battery?