I have a 3 car garage and considered various HVAC options but after running the numbers I decided that occasional heat is really what I needed. The garage is well insulated in the walls and 8" worth in the ceiling, also had the upgraded insulated garage doors installed when I built the house.
I have a large workshop in the basement area so the only work I usually perform in the garage is on the cars.
For years now I've been using a simple 23k BTU Kerosene heater and it knocks down the cold to mid 60's or better within 20 / 25 minutes or so, just have to crack one of the windows 1/2" or so. The $100 price tag enticed my cheap arse side...........