Hello:
Gasoline burning 24 volts air heater with output of 60,000 BTU. Will
easily warm 1200 sq. feet garage.  20, 000 BTU can be extracted from
exhaust to have hot water. You will need 500 watt 115/24 volt step-down
transformer and $3 full wave rectifier. Plug into 115 outlet and here
you go! Consumes 220 watts. Burns 1 gallon of gas in 2,2 hours.
Exhaust goes via pipe outside. NOS. $700.   Ark.