I came across this chart for available usage times for CPAP machines for a 100Whr battery

http://www.eu-pap.co.uk/super-cpap-battery-pack.html

So I suspect you will be needing something like a Solar PV system around the 600-1000W and an 80-100 AmpHr 12V LiFePo4 Battery system.

$1200 for the Solar PV Panels and $800 for the LiFePo4 Battery and $500 for the LiFePo4 Charge controller and cabling etc. i.e around $2500, but this will depend on how much sunny weather you have.