[aprssig] 8 hour Backup Power Rule

Scott Miller scott at opentrac.org
Tue Mar 18 11:15:38 EDT 2008

>    One thing with A/C is that it takes less than a watt from the grid to pump a
> watt of heat.  The only place you seem to get something for nothing.  

Assuming it's warmer inside, you're moving the heat 'downhill' anyway, 
aren't you?  And in any case, I think the lower bound of the energy 
required to move the heat would be determined by Carnot's theorem - 
you're not getting something for nothing if you can't get more energy 
back out of the system by reversing the heat pump.

To keep this on topic, someone mentioned the inefficiency of running a 
generator for a 10-amp battery charger.  I agree - my intent is to 
charge batteries only when the generator is already running, powering 
the fridge or whatever.  I've got a bit of solar charging capacity, too, 
but not enough to make much difference.

Here's a more practical question - at what level of load does a 
generator produce the most power per unit of fuel?


More information about the aprssig mailing list