Tools · 04
12V A/C Runtime Calculator
Every 12V air conditioner listing implies effortless all-night cooling. We installed one on our own van and took it to a festival in Tennessee July heat, and the real number was about 3 hours on LOW from a 100Ah battery — with a charger assisting. This calculator runs on that field data, not the brochure. When our amp-clamp curves publish, the defaults upgrade from FIELD to MEASURED.
Inputs
Solar after losses, or a DC-DC charger's real output. Our festival assist was a claimed ~270W.
Fridge, fan, Starlink… ours share the bank and average ~60–90W combined.
Where these numbers come from
- LOW ≈ 550W is field-implied, not clamped. Our 100Ah bank (≈1,280Wh nominal) emptied in ~3 hours on LOW while receiving a claimed ~270W assist. Depending on how much of that bank was truly usable, the implied draw is roughly 450–650W; we use 550W and label it. Amp-clamp curves are Test #2 on the bench.
- MAX = 960W is the manufacturer's claim, unverified, for our Vevor-branded unit's class. We are openly skeptical of the paired 12,000 BTU claim.
- Compressor cycling is not modeled. At a mild target temperature the compressor cycles off and real runtime beats this estimate; in July heat on LOW, ours ran essentially continuously.
- Inverter-based portables differ. The EcoFlow Wave 3 / Zero Breeze class has its own batteries and different loss paths — see that comparison.
The unit behind the data
The numbers on this page come from a Vevor-branded 12V mini split we bought at retail and installed on our own ProMaster. The white-label sibling listing on Amazon appears identical to our unit. That link pays us a commission; the runtime numbers above are exactly why we'd rather you size your battery bank before buying one.
Full context: the complete van A/C price ladder · budget split vs Dometic RTX vs Velit
Questions people actually search
How long will a 12V air conditioner run on a 100Ah battery?
In our real-world field test — a budget 12V mini split on its lowest mode in Tennessee July heat — a single 100Ah 12V battery lasted about 3 hours, and that was with a DC-DC charger feeding roughly 270W back in the whole time. Working backwards, the implied real draw on "low" is in the 450–650W range depending on the battery chemistry. Vendor marketing implies far longer runtimes; nobody publishing those numbers seems to have run the test.
How big a battery bank do I need to run a 12V mini split overnight?
Take 8 hours at our field-implied low-mode draw of ~550W and you get about 4,400Wh — roughly 430Ah of LiFePO4 at 80% usable, before the fridge and everything else. That is why "can I run A/C all night" is really a system-architecture question: big bank, alternator charging, and realistic expectations about low mode. Our overnight watt-hour logging will tighten this number.
Can solar keep up with a 12V air conditioner?
Not from a van roof. Even 600W of panels nets roughly 400–450W after real-world losses in perfect sun, which is below the field-implied draw of a budget mini split on LOW. Solar extends runtime; it does not sustain it. Our festival test demonstrated exactly this: the bank went flat with 400W of solar and a charger assisting.
Are these numbers measured or estimated?
Labeled, per number. The LOW-mode default is field-implied: derived from an observed 3-hour runtime on a known battery with a known assist, not from an amp clamp. The MAX default is the manufacturer claim. Instrumented amp-clamp curves per mode are the next test on our bench and will replace both — this page notes its own changelog when that happens.