Start here
Size the trip.
Then size the battery.
A fridge, lights and a laptop can make the same campsite feel very different from a phone-only overnight trip. Your own energy budget is more useful than a generic “weekend kit.”
Two ratings, two different questions
Watts (W) describe power at a moment in time. Check them to see whether a station can run your appliances together. Watt-hours (Wh) describe energy. A 20 W load running for five hours uses 100 Wh.
Write down a day at camp
Multiply each device’s measured watts by its daily running hours, then add the results. For appliances that cycle, use measured energy over a representative day or a realistic average power. A maximum nameplate rating does not necessarily describe continuous consumption.
| Illustrative load | Calculation | Daily energy |
|---|---|---|
| Fridge compressor | 45 W × 8 hours | 360 Wh |
| Laptop | 60 W × 2 hours | 120 Wh |
| Lights | 8 W × 4 hours | 32 Wh |
| Phone charging | 10 W × 2 hours | 20 Wh |
| Total | Example, not product test data | 532 Wh |
Allow for energy you don’t get to use
Devices do not receive every watt-hour printed on the battery. Conversion and station operation consume some energy. Using an illustrative 85% delivery efficiency gives 532 ÷ 0.85 ≈ 626 Wh from the battery per day, before any additional station overhead.
For two days without charging and a 20% planning margin: 626 × 2 × 1.2 ≈ 1,503 Wh. These assumptions are a starting point. Measure where possible and allow more reserve when losing power would spoil the trip.
Solar replaces energy; it doesn’t promise it
With four illustrative peak sun hours and a 75% yield factor, replacing that day’s battery draw plus the planning margin needs approximately 251 W of rated panels. This does not mean a 251 W panel delivers 251 W continuously, or that every campsite gets four peak sun hours.
Longer trips do not automatically need a proportionately bigger panel array if daily use stays constant and charging succeeds every day. More days without reliable charging do need more stored energy. Recovering after a run of poor weather needs extra charging capacity or reduced consumption.
Finish with the output check
Even a large battery may not support a high-power appliance. Add the simultaneous running loads and check startup requirements against the station’s continuous and surge specifications. Also check each individual DC or USB port.
Build your own energy budget →
Reference for load calculation: US Department of Energy, photovoltaic-system load sizing. Numerical camping scenarios and loss factors above are our explicit illustrative assumptions.