Yes, you can use it in your garage or workshop, but it is not a very good idea to use a personal AC in a garage. This is because it may not be able to perform that effectively, the way it would perform elsewhere. Although, you can use a personal AC anywhere where there is a plug, if the garage door is wide open or if the area is not well insulated then there are fewer chances of a drop in temperature. The same thing implies to your workshop. Instead, consider purchasing an evaporative AC for your garage as it won't make a difference if the door is left wide open or if there is improper insulation in that area.