Shop Heater??????

My suggestion wold be to go with radiant heat, it heats the objects in the shop not the air. We had them in the fab shop where I used to work, -40 below with the door open and you still felt warm. [long as there was no wind] shop was 60'x200'20'ceiling. I personally use wood and a propane furnace, heat up on propane when I first go out in the morning and in 15or 20min its warm and the wood stove keeps it warm, propane is expensive here. 24'x30' 8.5'ceiling. fully insulated.

I ended up with a hanging 80k propane unit.
Sofar works great and with a total cost w/a full 100gal of fuel = $723.00.
I will see how it is when we get below O and it will happen soon enough, we have all ready had mid 20s.
I even found a cool cover for the old chimmeny hole that I couldn't use with this heater.

Nobody has mentioned these, This is what I use to heat a 36x60, (155,000 btu). They come in all sizes kerosine(diesel) or propane.