My garage has horrible insulation. It can be old house, so it didn't have built up an insulated garage or garage door. So my garage feels colder than nature when winter rolls up to.
Radiant space heaters are compact and portable. They are great for immediately heating small materials. Many people will have them under their desk at the job to get hot just their space.
A cheaper and better option for consumption will surely portable garage heater. The big advantage of these types of heaters is they do not have to be constructed.
For a heater to get truly portable heater pros and cons, most will run off propane. Natural gas and electricity aren't quite as portable in many instances.