How to power a cpap machine on a boat?

[BlueH2Obound]

I use a CPAP as well. Look on the power supply that you plug into the 120v outlet. It will say input 120v, and output probably either 12v or 24v. The manufacturer of your CPAP probably sells a 12v, or 24v cord or power supply. Mine did. That would be the way to go if you are power limited. Since we installed a large LiFePO4 house batter bank and solar panels, I just run it using a standard 120v plug off of the inverter.

[GILow]

Many of these machines actually run on 12 volts, as already noted.

But also, many have a high start up current and so use a type of transformer that is pretty inefficient. The transformer packs have big capacitors in them to meet the start up demand.

If you cannot power the device directly from the 12v dc on the boat I do suggest you find out exactly how much power the transformer is using. You may find it is much more than expected.

FWIW, I've powered my old Respironics machine straight from the boat's dc for nearly ten years now without trouble. About 16AH per night.