A power station on its own is a nice energy store, but at some point it is empty. A solar panel on its own supplies power only in the daytime. A compressor cool box needs reliable power around the clock. Only the combination solves the problem: the solar panel harvests, the power station stores, the cool box consumes, a closed loop and days of self-sufficiency.
The key points in brief
- What power station size do I need for a cool box? A compressor cool box uses around 0.3 to 0.9 kWh per day.
- Which solar panel recharges the power station? As a rule of thumb, the solar output should roughly match the daily draw.
- Which battery technology is better for continuous operation? LiFePO4 batteries (LFP) last considerably longer than older Li-ion cells with over 3,000 charge cycles and are more temperature-stable, the better choice for camping and frequent use.
Details and reasoning in the article, FAQ at the end
Step 1: calculate daily consumption in watt-hours
Before you buy a power station, you should know how much power you use. Realistic guide values for typical camping appliances:
- 1× charging a smartphone: approx. 15 Wh per day
- 1× charging a laptop (office work): approx. 50 Wh per day
- 1× 40 litre compressor cool box: 460 to 680 Wh per day (depending on outside temperature)
- 1× kettle running for 5 minutes: 50 to 100 Wh
- LED interior lighting for 3 hours: approx. 30 Wh
- Charging a tablet: approx. 25 Wh
The cool box eats the biggest chunk. At a moderate 25 °C outside temperature, about 460 Wh per 24 hours. At 35 °C and constant lid opening, up to 680 Wh or more.
The formula for your minimum capacity
Daily consumption (Wh) × planned days without recharging × 1.2 (20 % buffer) = minimum capacity of your power station
Example: you use 600 Wh per day and want to bridge two days without sun: 600 × 2 × 1.2 = 1,440 Wh. A power station with 1,500 Wh would be ideal.
The 20 per cent buffer is a must: lithium batteries should be neither run down to zero nor operated permanently at the limit.
Step 2: how much solar input do I need?
Rule of thumb: power station capacity (Wh) ÷ 5 sun hours = required solar output (W)
The 5 sun hours are a realistic average for central Europe in the summer half-year. In high summer in southern Europe more like 6 to 7 hours, in April or September in Germany more like 3 to 4.
- Power station 256 Wh → approx. 50 to 60 W solar panel
- Power station 1,024 Wh → approx. 200 W solar panel
- Power station 2,048 Wh → approx. 400 W solar panel
Setup 1: solo weekend camper
You are travelling alone, set off Friday afternoon and come back Sunday evening. Beer cold, music in the evening, smartphone charged, nothing more.
Recommendation: EcoFlow RIVER 2 (256 Wh) + Mobicool MCF40 (in economy mode).
Daily consumption approx. 430 Wh. The 256 Wh of the RIVER 2 last half a day. Trick: charge the power station fully before departure and recharge it in the car via the vehicle adapter on the way there, so it is full again at the pitch. With a 60 or 100 W solar panel you get through the weekend relaxed.
Setup 2: vanlife couple
There are two of you, living in the van for several weeks, one works remotely, you cook for yourselves and don't want to look for a campsite every two days.
Recommendation: EcoFlow DELTA 2 with 1,024 Wh + Alpicool C40 compressor cool box + 200 W solar panel.
Daily consumption: cool box 500 Wh + two smartphones 30 Wh + laptop 50 Wh + light 50 Wh + kettle once 80 Wh = approx. 710 Wh. The 200 W of solar delivers around 1,000 Wh at 5 sun hours, realistically 800 Wh. That matches daily consumption, and you are self-sufficient for 5+ days.
Setup 3: family motorhomer
Four people, fridge, a film in the evening, more devices, more comfort.
Recommendation: EcoFlow DELTA 2 Max (2,048 Wh) + Dometic CFX3 35 + 400 W solar (roof-mounted).
Daily consumption: cool box 600 Wh + 4 smartphones 60 Wh + laptop/tablet 50 Wh + light 60 Wh + kettle 150 Wh + fan/TV 100 Wh = approx. 1,020 Wh. 400 W of solar harvests 1,600 to 2,000 Wh in good sun. Even with three days of grey sky the battery is enough, self-sufficient for 7+ days.
Worked example: how long does 1 kWh last in the cool box?
Calculation using the example of an efficient 40 litre compressor box in economy mode at 25 °C (consumption 460 Wh/24h):
1,000 Wh ÷ 460 Wh/day = approx. 2.17 days
A full 1 kWh power station keeps the cool box alone running for a good two days. In practice (with smartphone, light etc.) more like 1.5 to 2 days. At 35 °C and sun on the car, the cool box's consumption rises to 680 Wh, leaving just under 1.5 days.
Important: this calculation applies only to compressor boxes. Thermoelectric (Peltier) boxes draw power continuously and cool worse in heat. Why that technology is almost always the worse choice when parked off-grid is shown in the detailed comparison of cooling technologies at Campklar.
USB-C PD with 100 watts: why that is a killer feature
Modern laptops (MacBook Pro, Dell XPS, Lenovo ThinkPads) have charged via USB-C for years, up to 100 W. The PD 100 W standard covers exactly that.
If your power station has a 100 W USB-C output, you save yourself the original laptop power adapter completely. You only need a USB-C cable. That saves space, weight and the detour via the built-in 230 V inverter (10 to 15 % loss).
For power banks on the road a decisive criterion, see the comparison of XL power banks.
Practical tips for everyday use
- Pre-cool the cool box before departure: connect it to a socket at home the day before, which saves 30 % of power on the road.
- Align the solar panel: a panel lying flat on the roof loses up to 40 % of output when the sun is low. Aligning a folding panel to the sun almost doubles the yield.
- Shade is the enemy: even a branch over one cell can make the yield of the whole panel collapse.
- Protect batteries in heat: do not store LFP batteries permanently above 45 °C; place the power station in the shade.
- Use the kettle in the daytime: short high-load consumers drain the battery in minutes. Cook in the daytime, when solar power is directly available.
Verdict: which setup suits you?
Correct sizing is not a matter of belief but of arithmetic. If you add up your appliances once, multiply by the realistic days without a socket and add 20 % buffer, you arrive at the right setup.
Solo weekend camper: 256 Wh + small box + 60 W solar panel. Couple in a van: 1,024 Wh + 40 L box + 200 W solar. Family in a motorhome: 2,048 Wh + premium box + 400 W solar.
Important: better to buy one size bigger once than to upgrade again two years later. Current reviews and price overviews for power stations, compressor cool boxes and XL power banks are in our comparisons.
The same arithmetic logic specifically for camping, with a consumption table for cool box, light and laptop plus three worked example setups from the solo weekend to the family, is provided by the guide “Calculating power consumption when camping” at campklar.
Frequently asked questions
What power station size do I need for a cool box?
A compressor cool box uses around 0.3 to 0.9 kWh per day. For one day off-grid, a power station from about 500 Wh is enough; for several days or hot weather, 1,000 Wh and more makes sense, ideally with solar recharging.
Which solar panel recharges the power station?
As a rule of thumb, the solar output should roughly match the daily draw. A 100 to 200 watt panel usually offsets a cool box's consumption in good weather; in little sun, correspondingly more.
Which battery technology is better for continuous operation?
LiFePO4 batteries (LFP) last considerably longer than older Li-ion cells with over 3,000 charge cycles and are more temperature-stable, the better choice for camping and frequent use.