Get your free campervan electrical design (UK)
Answer a few quick questions about your van. You'll get a full design report: wiring diagram, cable sizes, fuse ratings, and a complete parts list.
Takes about 5 minutes · Free design report · No experience needed
Built on BS 7671 Section 721, Victron and Blue Sea guidance — we'll always tell you when a job needs a qualified electrician.
What does this calculator do?
Roam Wired is a free UK-based campervan electrical calculator that generates a custom wiring diagram and full parts list for your van conversion. It covers battery sizing (LiFePO4 and AGM), solar panel selection, DC-DC charger sizing, shore power, inverter calculations, wire gauges, and fuse ratings — all based on UK electrical standards.
Unlike generic electrical calculators, Roam Wired is built specifically for campervans and motorhomes. It accounts for the realities of off-grid van life: irregular solar input in UK conditions, mixed charging sources (solar + alternator + hookup), and the practical constraints of installing a 12V or 24V system in a moving vehicle.
The tool works for any van model — Mercedes Sprinter, Ford Transit, Volkswagen Crafter, Fiat Ducato, Renault Master, and others. Complete the 5-minute questionnaire to get your personalised system design.
Frequently Asked Questions
How do I calculate what size battery I need for my campervan?
To size a campervan battery, add up the daily amp-hour (Ah) consumption of all your appliances, then divide by your usable depth of discharge (typically 80% for LiFePO4). For example, 100Ah daily usage divided by 0.8 = 125Ah minimum battery. Our calculator does this automatically based on the appliances you select.
What size solar panel do I need for a campervan UK?
In the UK, a typical campervan solar setup needs 200-400W of panels to keep a 100-200Ah LiFePO4 battery topped up. The exact size depends on your power usage, van roof space, and how many cloudy days you expect. Our calculator accounts for UK solar irradiance averages to give you an accurate recommendation.
Is a LiFePO4 battery worth it for a campervan conversion?
Yes - LiFePO4 (lithium iron phosphate) batteries are now the standard choice for van conversions. They offer 80-100% usable capacity vs 50% for AGM, last 2,000-5,000 cycles, weigh half as much, and can be charged faster. The higher upfront cost is offset by a 10+ year lifespan.
Can I use this calculator for a Mercedes Sprinter, Ford Transit, or VW Crafter?
Yes. The Roam Wired calculator works for any campervan conversion regardless of van model - Mercedes Sprinter, Ford Transit, Volkswagen Crafter, Fiat Ducato, Renault Master, and others. The electrical system design principles are the same across all vehicles.
Does the calculator generate a wiring diagram?
Yes. After completing the questionnaire, Roam Wired generates a custom wiring schematic showing your battery bank, solar charge controller, DC-DC charger, bus bars, fuse positions, and appliance connections - sized to your specific system.
Built by van conversion enthusiasts. Calculations based on UK electrical standards and real-world testing. Always have your installation checked by a qualified electrician.