I am referring to ANY AND ALL breathing apparatus.
Energy does not disappear. It has to translate to motion, heat, magnetics, etc.
A programmed positive pressure fan, plus 30 watt heating resistance cannot "magically" consume a surplus of amperage. Any difference between a 300 dollar unit and six thousand dollar unit would be minimal. Say 120%.
"My humidifier uses more power than your humidifier because the wattage knows my unit costs more money?"
The PROM and energy management system within a BiPAP is minuscule compared to a non medical system.
Any finally
Look at the max power rating of your unit's power brick. My Respironic brick is rated for 5 amperes at 12.00 vdc.
In your wildest dreams, do you think Respironics would choose a MEDICAL power supply rated at or near maximum potential?
At full output on a cold* day, my brick heats to near 40c 104F.
*Do you sleep in 45F temperatures?
Measuring not guessing is the key to knowledge and meaningful planning.
I have a four thousand dollar Respironics unit apart. It failed when the owner tried powering it with an unregulated 7 ampere brick. The 5.0 volt logic system power supply chip failed. Perhaps (?) a 5.0 volt TO220 reg can be substituted but the board is 100% wave soldered.