Hi there, Marcel.

Depending on how handy you are, consider a used electric central furnace, that is, the kind used to heat an entire home.

While remodeling his home a few years ago, a friend installed a more modern heat pump unit, and gave me his old furnace. As I was looking to heat only a 24' x 24' insulated shop, I disconnected two of the three banks of heating coils. Otherwise, I made no modifications. I did cut some holes in the ceiling to install the inlet and outlet ports, but there's no reason that it couldn't be a free-standing unit in a garage. It is still thermostat controlled, so I can set the heat to any level I need to be comfortable. It's reasonably quiet, and with the big blower the whole space is evenly heated quickly. I was even able to install a filter assembly using a standard size (therefor cheaper) filter.

Since the market for used units has to be very small, I am guessing they are available quite cheap. My main costs were the heavy wire and a large enough circuit breaker in the shop's electric panel. Even with the two banks disconnected, I think I still needed something like a 50-amp breaker, or about twice as large as a normal household circuit uses. If you can do your own household wiring, this isn't too much of a step up in complexity. As in many projects like this, the money you save in purchase and installation compensates for some of the higher energy costs, say of electricity, that you use down the road.

Pete Roszyk,
in Snohomish, Washington