We used one in Vermont to heat a two story 1500 Sq ft house. The input was I believe 65,000 btuh. The space to non-combustible surfaces range from 18" to 30" depending on stove rating. At 40 lbs per bag and needing to keep them dry storage was a problem. You might need fresh air for combustion if you have a tightly sealed shop. It is imperative you keep the burner area clean, the pellets coat the burner "compartment" with a thick hard (1/8 to 3/8") carbon coating called "clinkers". The outer surface of the heat exchangers are easily cleaned, but again maintenance is paramount. If you do any wood finishing in your shop they are dusty, just pouring a bag of pellets in the hopper sends a dust plume in the air. I used a shop van when dumping pellets into the hopper and that wasn't enough to keep the dust down. Most use special double wall piping that can be pricey, depending on how far the flue run is. The piping is special because the stove operates on positive pressure so all the joints in the piping have a high temperature silicone seal to prevent flue gas leakage. They do put out heat when started in about 10 mins. Unlike a wood stove if you lose power they cannot be used as they operate on a 115 volt outlet. They require a special through the wall thimble to meet code requirements for combustible surfaces. If you have limited space the stove clearance to combustibles can me minimized through the use of sheet metal that is spaced off the wall I think 1/4". If you can store the pellets, don't mind the daily maintenance and dust, pellets might be the ticket for you. Just my two cents.
