What size battery do I need to run a 12V rooftop air conditioner in my RV?

Answered by RV Parts Giant · Upland, CA · November 9, 2026

Short answer: For one night, plan on about 400Ah of lithium. Our calculator counts a 10,000 BTU 12V rooftop unit at 750W, so 8 hours on a warm night is about 258Ah from the battery. Add a camper van's other loads and divide by 0.85, and one night comes to 400Ah, two nights 800Ah. A mild night drops it to 300Ah.

A 12V rooftop unit runs straight off the house battery with no inverter in between, which is why it costs roughly half the battery of a mains rooftop AC on the same night. Our calculator counts a 10,000 BTU 12V unit at 750W while the compressor runs. That works out to about 58.6A at 12.8V, close to the 58A that OutEquipPro lists for the Summit 2 in Turbo. Then it applies a duty factor for how much of the night the compressor is actually on.

Amp-hours the AC alone takes

Hours running	Mild night (70s, 35%)	Warm night (80s, 55%)	Hot night (90s+, 70%)
4 hours	about 82Ah	about 129Ah	about 164Ah
6 hours	about 123Ah	about 193Ah	about 246Ah
8 hours	about 164Ah	about 258Ah	about 328Ah
10 hours	about 205Ah	about 322Ah	about 410Ah

For a sanity check against the unit itself, the Summit 2's listed draws work out to about 168Ah for 8 hours in Eco (21A) and about 464Ah for 8 hours locked in Turbo (58A). The calculator's warm-night figure sits between those two, which is how a unit that cycles behaves.

The bank for the whole rig

The battery also runs everything else, so the calculator adds the AC to the rig's daily use, multiplies by the nights off-grid, divides by 0.85 so a LiFePO4 bank is never drained flat, and rounds up to the next 50Ah.

Rig, 8 hours of 12V AC	Mild	Warm	Hot
Camper van preset (69Ah/day), 1 night	300Ah	400Ah	500Ah
Camper van preset, 2 nights	550Ah	800Ah	950Ah
Travel trailer preset (37Ah/day), 1 night	250Ah	350Ah	450Ah

Refilling it is the harder part

Sizing the battery is only half the job. Putting 327Ah back in a day, the van on a warm night, takes about 1,150W of solar at 5 peak sun hours using the calculator's 75% harvest factor. That is more panel than most van roofs hold. So most 12V AC owners lean on a DC-DC charger while driving, or cool the rig hard before bed and let it coast.

Check two things on the unit you choose: its rated current, and that your battery's continuous discharge rating covers it. Then run your own numbers in our RV solar & battery calculator. Pick "12V rooftop AC", set your hours and how hot it gets, and it sizes the bank and the solar together.