Free campervan electrical design tool
Get a complete electrical design. Not just a battery number.
Tell us what you want to power. Roam Wired turns your appliances and travel style into a calculated system with a wiring diagram, correctly sized components, cable and fuse schedules, and a parts list.
Your finished output
One plan you can actually build from
Interactive wiring diagram
See how every major component and connection fits together.
Battery and charging sizes
Size the battery bank, solar, DC-DC charging and inverter from your loads.
Cable and fuse schedule
Get calculated cable sizes and protective fuse ratings for each circuit.
Complete parts list
Turn the design into a practical shopping list with compatible components.
Live safety checks
Catch undersized cables, missing protection and design conflicts while you edit.
Downloadable design report
Keep the diagram, calculations and schedules together for your build.
Start your electrical design
Choose the route that suits you.
Answer plain-English questions for the quickest result, start from a proven electrical template, or open a blank canvas if you already know what you need.
What you get for free
Every important electrical decision in one design.
Instead of collecting disconnected calculator results, you get a system where the loads, components, cables, fuses and costs update together.
Interactive wiring diagram
See how every major component and connection fits together.
Battery and charging sizes
Size the battery bank, solar, DC-DC charging and inverter from your loads.
Cable and fuse schedule
Get calculated cable sizes and protective fuse ratings for each circuit.
Complete parts list
Turn the design into a practical shopping list with compatible components.
Live safety checks
Catch undersized cables, missing protection and design conflicts while you edit.
Downloadable design report
Keep the diagram, calculations and schedules together for your build.
How it works
From appliance list to buildable electrical plan.
Tell us what you will power
Choose your fridge, lights, laptops, cooking equipment and other loads, then add how long you use each one.
We calculate the complete system
The tool sizes storage, charging, solar, inverter, cables and protection using UK-localised assumptions.
Review, edit and export
Fine-tune the live diagram, swap parts and download the information you need to plan the installation.
Designed to help you plan—not to hide the calculations.
See the assumptions, review all 42 checks and have mains-voltage work verified by a qualified professional.
What does the electrical design tool 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.