Nearly every portable air conditioner question starts as “how many BTU do I need?” and ends somewhere else entirely — at how you are going to power the thing. BTU is the easy part. Runtime is what decides which unit you should actually buy.
Step 1: size by the space, not the rig
A portable unit cools the volume of air around it, so what matters is the enclosed area you are trying to hold cool, not what the vehicle is called.
| Space | Rough area | Sensible capacity |
|---|---|---|
| Two-person tent, truck cab, rooftop tent | Under 60 sq ft | ~2,000–4,000 BTU |
| Van build, teardrop, small camper, family tent | 60–130 sq ft | ~4,000–5,500 BTU |
| Larger camper or a space that heats up through the day | 130–150 sq ft | 5,000 BTU and up, well insulated |
Two things shift you up a size regardless of area: sun on an uninsulated metal roof, and people. A sealed, shaded, insulated van holds temperature far better than a bare panel van baking in an open campground.
Step 2: the power budget is the real constraint
This is the step most buyers skip. A portable AC is a compressor, and a compressor draws real power for hours, not minutes.
Take the Zero Breeze Mark 3 as a worked example, using its published figures: 500W rated input when cooling, and a stated minimum draw of 150W once it is holding temperature rather than pulling it down. Pair it with the Mark 3 Smart Battery at 1,022Wh and the arithmetic is straightforward:
- 1,022Wh ÷ 500W ≈ 2 hours of hard cooling on one battery
- 1,022Wh ÷ 150W ≈ 6–7 hours once the space is cool and the unit is cycling
Those are the two ends of the range. Where you land depends on insulation, outside temperature and how cold you set it — which is exactly why a single “hours of runtime” number on any spec sheet should be read as a best case, ours included.
The practical consequence: one battery gets most people through the first part of a night, not all of it. If you want to wake up cool, plan on two. Mark 3 batteries chain up to five units, and a 100W solar kit recharges them during the day so you are not starting each evening from empty.
Step 3: battery-integrated, or bring your own power station?
This is the actual fork in the road, and it matters more than a couple of hundred BTU.
Battery-integrated. The Zero Breeze Mark 3 runs on its own 48V battery that plugs straight in, with no inverter and no conversion losses in between. It is the tidier system, it is designed as one thing, and you can stack capacity as your trips get longer. You pay for that integration.
Power-station powered. The Cybertake S2 Pro and S1 Pro are built to run off a general-purpose portable power station. If you already own one — and plenty of people do — you are buying only the air conditioner, and the same battery still charges your laptop, lights and fridge. That is a genuinely better answer for a lot of setups, and it costs less.
So: already own a decent power station, or want one battery that does everything? Look at Cybertake. Want a single purpose-built cooling system with stackable batteries and matched solar? Look at Zero Breeze.
The three units we stock, side by side
| Cybertake S1 Pro | Cybertake S2 Pro | Zero Breeze Mark 3 | |
|---|---|---|---|
| Cooling | 4,100 BTU | 5,100 BTU | 5,280 BTU |
| Heating | — | 6,100 BTU | 5,800 BTU |
| Coverage | Tent, small camper | Up to 130 sq ft | 100–150 sq ft |
| Weight | 21.6 lb | 25.6 lb | Just under 22 lb |
| Power | 48V DC | 48V DC | 48V DC, 500W rated / 150W min |
| Battery | Bring your own | Bring your own | Dedicated 1,022Wh, stacks to 5 |
| Quoted efficiency | Up to 8 hrs on 1 kWh; 38 dB sleep mode | Up to 8 hrs on 1 kWh in Eco+ | Cools 20°F in 5 minutes; 61–88°F thermostat |
On raw cooling per dollar the Cybertake units win, and we would rather say so than pretend otherwise. What the Mark 3 adds is the matched battery and solar ecosystem, a heating mode alongside the S2 Pro's, dehumidify and fan modes, and R290 refrigerant. Whether that is worth the difference depends entirely on whether you already have a power station.
Step 4: venting is not optional
Every unit on this page is a real compressor air conditioner, which means it moves heat rather than destroying it. If the hot exhaust stays in the space, the unit is heating and cooling the same air and you will not get cold. This is the single most common reason people conclude a portable AC “does not work”.
- Van conversions: a window venting kit cut for Mercedes Sprinter, Ram ProMaster or Ford Transit, or a universal DIY panel if you are cutting your own.
- Tents: the tent venting kit seals around the duct through the tent wall.
- Boats: the dual-duct marine window kit.
- Permanent installs: add a mounting kit so the unit does not move in transit, and hose insulation to stop heat bleeding back through the ducting.
Budget for the venting kit at the same time as the unit. It is not an upsell; it is the difference between a cold van and a warm one.
Short answers
Tent camping, already own a power station. Cybertake S1 Pro, plus a tent venting kit.
Van build, already own a power station. Cybertake S2 Pro, plus the window kit for your van.
Van or camper, no power station, want one purpose-built system. Zero Breeze Mark 3 with two batteries and a solar kit, plus the window kit for your van.
Year-round use. Anything with a heating mode — the S2 Pro or the Mark 3.
Browse everything in portable air conditioners, or the full Zero Breeze range.
Specifications above are the manufacturers' published figures. Runtime estimates are arithmetic from those figures and will vary with insulation, outside temperature and set point.