Electrical System Planner
Calculate your solar, battery, and inverter requirements
Select the appliances you plan to use in your campervan, adjust usage hours, and get personalised recommendations for your battery bank, solar panels, inverter, and charge controller. All calculations account for real-world efficiency losses.
Main cabin LED strip or panel lights
Bedside or spot reading lights
Awning or under-van lighting
USB phone charging (5V 2A)
Laptop charging via inverter
Tablet or e-reader charging
Action camera or drone battery charging
12V compressor fridge running intermittently (avg draw)
Thermoelectric cool box (runs continuously)
12V pressure water pump for sink
12V kettle (slow — takes 20-30 min)
Espresso or pod machine — heavy draw, needs large inverter
Diesel heater fan and controller (fuel not electrical)
Powered roof ventilation fan
Small clip-on or desk fan
Small 12V immersion heater for warm water
Pressure pump for shower system
Portable speaker charging
12V TV or portable monitor
Nintendo Switch or similar (via inverter)
Portable USB-C monitor for remote work
Mobile WiFi hotspot or router
Starlink satellite internet terminal
Carbon monoxide detector (always on)
Smoke detector (always on)
Rear-view camera system
Inverter idle/standby consumption when left on
How many cloudy days should your batteries last?
Peak sun hours per day for your region
Peak draw: 50.7W · 5 appliances
100Ah
Need: 24Ah · 80% usable · Est. £300–£600
Lighter, longer life, deeper discharge. Best for van builds.
110Ah
Need: 38Ah · 50% usable · Est. £110–£220
Cheaper upfront but heavier, shorter life, less usable capacity.
100W
Need: 35W · 80% efficiency · Est. £80–£200
1-2 panels on roof
300W
Peak load: 64W (with 25% headroom) · Est. £40–£120
Pure sine wave — suitable for laptops and small devices
20A MPPT
Need: 11A · Est. £30–£80
MPPT controllers are 20-30% more efficient than PWM.
Important: These are estimates based on typical usage. Actual consumption varies with temperature, battery age, and usage patterns.
Consider adding a B2B (battery-to-battery) charger to charge from the alternator while driving — this supplements solar significantly in the UK.
For UK winters, size your system for 2 peak sun hours to ensure reliability.
| Appliance | Category | Watts | Hours/Day | Wh/Day | % of Total |
|---|---|---|---|---|---|
| LED Main Lights | Lighting | 10W | 5h | 50 | 45% |
| Phone Charger | Charging | 10W | 3h | 30 | 27% |
| Water Pump | Kitchen | 30W | 0.5h | 15 | 13% |
| CO Alarm | Safety | 0.5W | 24h | 12 | 11% |
| Smoke Alarm | Safety | 0.2W | 24h | 5 | 4% |
| Total | 112 | 100% | |||