YOUR ENERGY PROFILE.
This document contains the sizing of your future electrical installation, calculated based on your appliances.
Inventory:
Battery
To guarantee 0WH without damaging your bank (80% max discharge):
Solar
Minimum power required to recharge your consumption:
220V AC
Maximum power (with 25% safety margin).
12V Cable Sizing Guide
Use this professional reference table to select the correct gauge (mm²) for your cables. For 12V in a van, the maximum tolerated voltage drop is 3%. Always use multi-stranded flexible automotive wire.
| Current (A) | Round trip < 2m | Round trip 4m | Round trip 6m |
|---|---|---|---|
| 5A (LEDs, USB) | 1.5 mm² | 2.5 mm² | 4 mm² |
| 10A (Fridge, Pump) | 2.5 mm² | 4 mm² | 6 mm² |
| 20A (Heater) | 4 mm² | 10 mm² | 10 mm² |
| 50A (DC/DC Booster) | 10 mm² | 16 mm² | 25 mm² |
| 100A (Inverter) | 25 mm² | 35 mm² | 50 mm² |
Fuse Sizing
The fuse protects the wire, not the appliance. Always place it as close to the power source as possible (battery or busbar).
- Wire 1.5 mm² → Max fuse 10A
- Wire 2.5 mm² → Max fuse 20A
- Wire 4 mm² → Max fuse 30A
- Wire 6 mm² → Max fuse 40A
- Wire 10 mm² → Max fuse 60A
SCHÉMA ÉLECTRIQUE
PANNEAUX SOLAIRES
0W
REGULATEUR MPPT
BATTERIE AUXILIAIRE
0 Ah
Lithium LiFePO4
BOÎTE À FUSIBLES 12V
Pompe, Leds, Frigo...
CONVERTISSEUR 220V
NON REQUI
SHOPPING LIST
Where to find this equipment? Here is the community-approved selection.
12V 6-way Fuse Box
Mandatory protection
Digital Multimeter
Test your connections
Heavy Duty Crimping Tool
For perfect lugs
Heat Shrink Tubing
Insulation and safety
Comparison table
| Panel watts | Wh/day summer (US SW) | Wh/day summer (UK) | Wh/day winter (UK) |
|---|---|---|---|
| 100W | 650-750 | 500-600 | 100-150 |
| 200W | 1,300-1,500 | 1,000-1,200 | 200-300 |
| 300W | 1,950-2,250 | 1,500-1,800 | 300-450 |
| 400W | 2,600-3,000 | 2,000-2,400 | 400-600 |
About this tool
Sizing a campervan solar system starts with energy consumption — not panels. The formula works backwards from your daily energy budget to the solar array size needed to replenish it. This approach prevents the most common mistake: buying panels based on roof space before calculating actual needs.
Step 1: Daily energy budget. List every device with its rated wattage and average daily hours of use. Typical comfortable van life setup: 12V compressor fridge (380Wh/day at 22°C ambient), LED lighting (50Wh/day), laptop (480Wh/day if working), phone charging (20Wh), USB accessories (30Wh), water pump (15Wh/day). Total: 975Wh/day for a working nomad, 495Wh/day for a weekend lifestyle.
Step 2: Battery sizing. Target 2 full days of autonomy without any charging, then calculate: Wh needed = Daily consumption × 2 days ÷ battery efficiency (0.9 for LiFePO4, 0.8 for AGM). For 975Wh/day: 975 × 2 ÷ 0.9 = 2167Wh → 180Ah LiFePO4. Round up to 200Ah.
Step 3: Solar sizing. Peak solar hours (PSH) vary by location: UK/Germany average 2.5-3.5h, France/Spain 4-5h, Portugal/Italy/Greece 5-6h in summer. Formula: Solar watts = Daily Wh ÷ PSH × 1.25 safety factor. For 975Wh/day in France (4.5 PSH): 975 ÷ 4.5 × 1.25 = 271W. Nearest practical: 300W (two 150W or three 100W panels).
Step 4: MPPT controller. Size at 125% of panel short-circuit current. Two 150W panels in series: Isc = 9.72A per string, combined 9.72A (series maintains current). MPPT output at 12V: 300W ÷ 12V × 1.1 = 27.5A. Use a 30A controller minimum — Victron SmartSolar MPPT 75/30 (€120) is the standard choice, handles up to 430W.
Step 5: Cable sizing from panels to controller. The panel string carries up to Isc current (9.72A for this example). 6mm² cable for runs up to 8m, 4mm² for up to 5m — this keeps cable voltage drop under 1.5% at full current.
Variables that change your solar calculation: travelling north of 52° latitude in October-February (PSH drops to 1-2h — you need 2-3× the summer panel capacity or rely more on driving/shore charging). High roof campers (L3H3 Transit) have 4m² of usable roof vs L2H2 Transit at 2.5m² — significantly more panel capacity available. Climbing mountains reduces sun angle efficiency but also reduces ambient temperature (increases panel efficiency by 0.5%/°C).
Advanced shading analysis for van roof installations: if any part of your solar array is shaded for even 1-2 hours per day (a roof vent, antenna, or overhanging trees at a regular camping spot), use bypass diodes or wire panels individually to the MPPT rather than in series strings. A single shaded 200W panel in a 400W series string reduces the entire string to the shaded panel output — potentially halving production. Separate inputs or parallel wiring eliminate this shading penalty.