How big a battery do I need to run a CPAP in my RV overnight?

Answered by RV Parts Giant · Upland, CA · October 11, 2026

Short answer: Our calculator counts a CPAP at 15Ah a night at 12V, and 30Ah with the heated humidifier on. With the rig's basic loads that is a 100Ah LiFePO4 battery for one night, 150Ah for two nights and 200Ah for three with the humidifier. Check your machine's label and use its maker's DC cord or power supply.

This is power sizing only, not medical advice. If you rely on the machine, plan your backup power with your equipment provider. Your machine's label and manual come first. The figures below are the averages our calculator uses, and they are a starting point, not a measurement of your machine.

The figures the calculator uses

Load	Amp-hours a night (12V)
CPAP, humidifier off	15
Heated humidifier and hose, extra	15
Rest of the rig: lights, water pump, phone charging, vent fans	18 a day

The heated humidifier doubles the CPAP's share because heating is where the watts go. The blower itself is a small fan load. The calculator treats the CPAP as running on 12V, so no inverter is added. Run it through an inverter instead and you also pay the inverter's idle draw and conversion loss.

Battery and solar by number of nights

With no fridge running, just the basic loads and the CPAP:

Setup	Daily use	Nights	Battery	Solar
CPAP, humidifier off	422Wh	1	100Ah	150W
CPAP with humidifier	614Wh	1	100Ah	200W
CPAP with humidifier	614Wh	2	150Ah	200W
CPAP with humidifier	614Wh	3	200Ah	200W

The battery follows the formula daily amp-hours x nights / 0.85, because the calculator plans on using about 85% of a LiFePO4 bank. Add a 12V compressor fridge and the daily figure rises by another 25Ah, so size the full rig, not just the machine.

A separate battery just for the CPAP

Some people keep the CPAP off the house bank so a flat coach battery cannot stop it overnight. On the calculator's figures, the CPAP with humidifier uses about 384Wh a night (30Ah x 12.8V). The BLUETTI X60 CPAP Power Bank holds 614Wh, so it covers one night with that load, with margin, before any conversion loss, but not two. Check that your machine's input matches one of the X60's outputs before relying on it.

Measure it

Fit a SmartShunt and run the machine for a night on the battery at home. The overnight drop in amp-hours is your real number, and it replaces the 15Ah or 30Ah estimate in every row above.

Run your own numbers in our RV solar & battery calculator: tick the CPAP and the humidifier along with the rest of your loads.