Size your camper's electrical system
List the appliances you will use and get the battery, solar panels, charge controller, inverter, cables and fuses you need.
Your appliances
Description
List everything you will plug in. It is used to measure your daily consumption in watt-hours (Wh): watts × hours of use × units. Everything else follows from that figure.
Tap what you will use
How you travel
Description
Three questions about how you use your camper. They adjust the size of each component: more days without charging need more battery, and less sun needs more panels. Under advanced options you can change the voltage and the cable lengths.
Advanced options
Cable length between components, in metres (one way)
What you need
Description
The minimum size of each component to cover your consumption: the battery in amp-hours (Ah), the panels and inverter in watts (W), the controller in amps (A) and the thickness of each cable in mm², with the fuse that protects it.
You have changed some data. Press Calculate to update the result.
Details for the build: cables and fuses
Cables and fuses
| Run | Current | Cross-section | Fuse | Drop |
|---|
Shopping list
Description
Every component of the installation with its size, ready for comparing prices. At the end you get the equivalent portable power station, in case you would rather not install anything.
To understand it better
Worked example
A van with a compressor fridge, LED lights, phone charging and a laptop, for 2 days without charging in spring, needs about 911 Wh per day. That means a 200 Ah lithium battery, 350 W of panels, a 40 A controller and a 300 W inverter.
Typical consumption
| Appliance | Power | Use per day | Consumption per day |
|---|---|---|---|
| Compressor fridge | 45 W | 10 h | 450 Wh |
| LED lights | 15 W | 4 h | 60 Wh |
| Water pump | 60 W | 0.2 h | 12 Wh |
| Phone charging (USB) | 20 W | 2 h | 40 Wh |
| Roof fan | 25 W | 5 h | 125 Wh |
| Parking heater | 30 W | 6 h | 180 Wh |
| Router 4G | 10 W | 8 h | 80 Wh |
| Laptop | 60 W | 3 h | 180 Wh |
| TV | 50 W | 2 h | 100 Wh |
| Coffee machine | 1,000 W | 0.1 h | 100 Wh |
| Hair dryer | 1,200 W | 0.1 h | 120 Wh |
| Microwave | 900 W | 0.1 h | 90 Wh |
| E-bike (charger) | 150 W | 3 h | 450 Wh |
Indicative values. Check the label on your appliances for more precision.
Common mistakes
- Forgetting the small loads that are always on, such as the router, chargers or the inverter itself on standby.
- Sizing the panels with summer sun and then travelling in winter too.
- Buying a bigger inverter than you need: it uses more on standby and forces much thicker cables.
Questions about this tool
Can I charge the battery with solar panels alone?
Yes, if the panels cover your consumption at the time of year you travel. In winter or on cloudy days it is wise to have a second source, such as an alternator charger.
What if I add appliances later?
Calculate again with the new list. The battery and the cables are the most expensive parts to upgrade, so it pays to leave some margin from the start.
Why is the inverter cable so thick?
Because at 12 V an inverter draws a lot of current: 1000 W is more than 80 A. That is why it is fitted close to the battery, with the cable as short as possible.