93% Efficient Gas Fireplace

[MountainDon]

Interesting find... a propane or natural gas (different models) fireplace with up to 28,000 BTU (input), in three stages, L-M-H. Exhaust temp is 120-130 degrees F and can use PVC as exhaust pipe. The only drawback for off-grid use is it has a 3 speed blower... needs electricity.

http://www.gas-space-heater.com/empire-mantis.html

Oh yeah, and it's pricey like a lot of really cool stuff.