From: peterwieck33@gmail.com   
      
   OK - the typical heated CPAP device will consume 100 watts per hour if   
   heated.  I am going for the extreme case for safety.   
      
   a) Assume you will use it 8 hours per day, for three days.    
   b) Assume a 10% self-discharge rate for (3.3% per day).   
   c) Assume that you will want 200% of necessary capacity - that is, discharge   
   the back-up device to no lower than 50% to avoid damage to the batteries.    
      
   3 x 8 x 100 x 2 = 4,800 watts.   
      
   Allowing for losses, and self-discharge as-noted. You will need a device   
   capable of supplying 48 amp-hours at 120 VAC.    
      
   Without redundancy (dangerous). your typical 1500 watt UPS will operate at   
   roughly 3 hours per 100 watts, without damage, and run in the $500 - $700   
   range.    
   You will need eight (8) of them to meet your most basic need. And have to   
   change them twice (2x) per night. Or, you could spend $3,500 for a single unit   
   that could run for all of eight hours at 100watts.    
      
   Get a generator. Be wise in your fuel selection. You will have four (4)   
   choices:   
   a) Gasoline: Gasoline generators are amongst the cheapest of options, and even   
   a relatively small one will run all critical functions in the typical   
   household including your refrigerator, some lights and the CPAP. It will burn   
   something on the order of 1.   
   3 gallons of fuel per hour. So, you will need to store 30+ gallons of fuel   
   on-site, and fill it as needed. At night. Or 94 gallons and run it 24/7.   
   Gasoline devices tend to be either large, powerful and noisy, or small, quiet   
   and low power. Anywhere from    
   $400 - $1,000 will get you there. No transfer switch, strictly a manual   
   device.    
   c) Diesel fuel: This would be a whole house device, and if installed with the   
   proper transfer switch, and with a large tank, you could get up to a week with   
   such a device. But they are not cheap. You would start around $1,500 without   
   installation or a    
   transfer-switch. So, figure $3,500 absolute minimum installed.  And that would   
   be for a Chinese-origin device. A decent Kohler device would be about $4,500   
   installed.    
   d) Natural gas: If you have a reliable source of natural gas - about the same   
   installed cost as a diesel - and no fuel limits. By far, the cleanest, lowest   
   maintenance option, and least expensive to operate.    
   e) Propane:  As above, but you would need a large propane tank with the   
   associated issues.    
      
   The issue with medical devices is that one does not want to screw around with   
   'good enough' - as that 3-day issue might turn into a 4 or 8 day issue.   
      
   Peter Wieck   
   Melrose Park, PA   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)