Came across this in an RV book. Comes from Europe so not sure if it is available here in the US yet but it sounds like a great alternative to generators while boondocking.
http://www.efoy-comfort.com/
I don't know how much it costs per month to run a generator while boondocking, but this costs about $100 per month for the fuel cartridges.
Have any of you heard of this or know someone who has used it?