Building a van life solar system involves mounting solar panels on the roof, connecting them to an MPPT charge controller, wiring the controller to a lithium battery and connecting an inverter for AC appliances. A typical van build uses 200W to 400W of panels and a 100Ah to 200Ah lithium battery, which covers lighting, device charging, a compressor fridge and a diesel heater fan for several days between charges.
A well-designed van solar system gives you genuine independence. No hook-up fees, no generator noise, no worrying about finding a campsite with electric. This guide covers the entire build from planning to final wiring, written for people converting a transit-style van to a full-time or part-time home.
Planning Your System
Calculate your daily energy use
Start by listing every electrical device in the van and how long you run it daily. Common van life loads include a 12V compressor fridge (around 30 to 50Wh per hour depending on ambient temperature), LED lighting (5 to 15W), phone and laptop charging (around 100Wh per day combined), a diesel heater fan (15 to 30W when running), and a 12V water pump (minimal draw). Add everything up to get your total daily Wh requirement.
A realistic total for a solo or couple van life setup is typically 300 to 600Wh per day.
Decide on battery capacity
You want enough battery capacity to run for 2 to 3 days without sun. For a 400Wh daily requirement, that means 800 to 1200Wh of usable battery capacity. Lithium iron phosphate (LFP) batteries can be discharged to around 90% of rated capacity, so a 100Ah 12V LFP battery (1200Wh rated) gives you roughly 1080Wh usable. Two 100Ah batteries in parallel give you 2400Wh rated or around 2160Wh usable, which is comfortable for most van setups.
Size your solar panels
The UK averages 2.5 to 4 peak sun hours per day depending on season and location. Divide your daily Wh requirement by peak sun hours and add 25% for losses. For 400Wh per day at 3 peak sun hours: 400 / 3 x 1.25 = 167W. Round up to 200W to 300W for a comfortable margin. Two 100W rigid panels or a single 200W panel fits most transit van roofs alongside a roof vent.
Component List
- Solar panels (200W to 400W, monocrystalline rigid)
- MPPT charge controller (sized for your panel array and battery voltage)
- Lithium iron phosphate (LFP) leisure battery (100Ah to 200Ah at 12V)
- Pure sine wave inverter (if you need AC, 1000W to 2000W)
- Battery monitor (e.g. Victron BMV-712 or similar)
- Fuses and a main isolation switch
- Correctly rated DC cabling
- MC4 connectors and solar cable
- Cable entry gland for roof penetration
- Battery box or secure mounting for the battery
Mounting the Solar Panels
Rigid panels mount to the van roof using aluminium Z-brackets or channel mounts. Drill through the roof and use stainless steel bolts with rubber washers to prevent water ingress. Apply sealant (Sikaflex 521 or similar) around every roof penetration. Route the solar cables through a waterproof cable entry gland.
Avoid mounting panels flat against the roof with no air gap. A 25 to 50mm gap allows airflow underneath, reducing panel temperature and improving efficiency.
Installing the Charge Controller
Mount the MPPT charge controller in a ventilated location inside the van, away from the bed and living area (it can run warm). Connect the battery first, then the solar array. Always follow this sequence to avoid damaging the controller. Set the battery type to lithium and configure the absorption and float voltages according to your battery manufacturer's specifications.
Battery Installation
Mount the battery securely so it cannot move in a collision or sharp braking. Lithium batteries can be mounted in any orientation. Install a main fuse within 150mm of the battery positive terminal. An isolation switch between battery and the rest of the system is strongly recommended.
If your van has an alternator, consider a DC-DC charger (B2B charger) to charge the leisure battery while driving. This protects the vehicle's alternator and provides a controlled charging current to the lithium battery.
Wiring the Inverter
Connect the inverter directly to the battery with short, thick cables (typically 25mm to 50mm depending on the inverter's rated current). Fuse the positive cable close to the battery. A 1000W inverter at 12V draws up to 100A, so cable sizing and fusing must be appropriate. Run AC outputs from the inverter to standard 13A sockets inside the van.
Adding a Battery Monitor
A battery monitor is one of the most useful additions to any van solar system. It measures current in and out of the battery and gives an accurate state of charge reading. Without one, you are guessing. With one, you know exactly how much capacity you have and whether your solar is keeping up with your consumption.
Testing the System
Before using the van, test each component in sequence. Check that the charge controller shows panel input in sunlight. Verify the battery voltage is correct. Test the inverter with a small AC load. Run the fridge for 24 hours and monitor the state of charge to confirm your sizing assumptions were correct.
UK Legal Requirements
Electrical work in a vehicle does not fall under Part P building regulations (which covers domestic properties), but you are responsible for ensuring the installation is safe. Use correctly rated components, fuse every circuit appropriately and have the work checked by a qualified auto-electrician if you have any doubts. There is no requirement to notify anyone for a leisure vehicle electrical installation, but the quality of the work directly affects your safety.
