Can a lithium battery bank run an RV roof air conditioner for 8 hours off-grid?

Answered by RV Parts Giant · Upland, CA · September 29, 2026

Short answer: Not with a bank most rigs can carry. A 13,500 BTU roof unit draws roughly 1,300 to 1,500 watts, about 110 to 130 amps at 12 volts, so a 280Ah bank gives about two hours and two 280s about four. The workable design is lithium for everything else, and a generator or shore power for the air conditioner.

The arithmetic

A 13,500 BTU roof air conditioner draws roughly 1,300 to 1,500 watts while running. From a 12 volt bank that is around 110 to 130 amps. Divide a bank's capacity by that and you get the runtime:

Bank	Approximate A/C runtime
200 Ah	About 1.5 hours
280 Ah	About 2 hours
400 Ah	About 3 hours
560 Ah (two 280s)	About 4 hours

Eight hours would need roughly twice the largest bank in that table, before counting the fridge, lights and fans. A bank that size is heavy, needs a place to live, and costs more than the generator it would replace. That is why the honest answer to "eight hours on batteries" is no for most vans and trailers.

What lithium does replace

Everything else. Lights, water pump, fans, a 12 volt fridge, electronics and the microwave through an inverter all run from a single 280 amp-hour bank for a weekend without the generator starting. So the design that works is lithium for the loads, and the generator or shore power for the air conditioner.

Make the generator hours short

When the generator runs, make every hour count. A MultiPlus inverter-charger charges at up to 120 amps, about twice a typical factory converter, so the bank refills in half the time while the A/C runs. Solar through a SmartSolar MPPT covers the daily draw of the other loads, and an Orion XS puts charge in from the tow vehicle or chassis while you drive, so you arrive full.

If animals or people depend on the cooling

Do not plan on batteries alone to keep a space cool through a hot afternoon. Plan for a generator or shore power to carry the air conditioner, and use the lithium bank for everything else and as a short bridge. A SmartShunt on the battery negative shows the real state of charge and time remaining, which matters because lithium voltage stays nearly flat until the bank is almost empty.

Send us the air conditioner model, your bank and how many hours you need and we will size the rest. Everything ships from Upland, California.