First, as for the Kill-a-Watt meters: I've always been a bit skeptical of the accuracy, especially for something the varies as fast as a CPAP , but they do seem to give an approximate answer.
A modern pump will use about 50 to 60 Watt-hours a night, with the humidifier/heated hose adding up to 5 to 7 times as much depending on the ambiant conditions and settings. About 250 Watt-hours, or 0.25 kWh per night might be a reasonable first guess of the power used. This would be maybe 7-8 kWh a month, or a few bucks in most places.
Woody wrote:Well my let's see my Resmed power supply says 2.5 A MAX BUT note it says MAX and
I take it that that is saying for a fraction of a second when you first turn it on it may
pull 2.5 and that would calculate as ~ 260 watts
Those are amps at 24 Volts DC so its 60 Watts at 120 plus about 10% overhead. That's about the same as the Respironics without the heated hose - the supply is 90 watts for the heated hose version.
There is a startup hit on the pump of around 2-3 amps (24-36 watts) for the Respironics; i've haven't measured Resmed.
Woody wrote:But in real life it pulls about 10 to 15
watts without the humidifier. I actualy measured how much my resmed set at 14 ' drew
from a 12v backup power supply and it was only about .6 A ( my memory is hazy perhaps
it was as high as .7 A ) But an APAP will draw more but still not all that much more.
Yes, roughly half an amp load on a 12V battery is normal for the pump alone. The mechanics of a CPAP and an APAP are virtually identical so there shouldn't be much, if any difference. A far as I know a Respironics 460 is the simply a locked 560. You could argue that the CPAP actually uses more power since it has to be set at a higher level.
Hark, how hard he fetches breath . . . Act II, Scene IV, King Henry IV Part I, William Shakespeare