Yes, you can store a pressure washer during the winter in an unheated garage. However, there are some precautions you must take. First of all, you definitely want to either drain the gasoline out of the tank or you can mix fuel stabilzer into the existing fuel. Secondly, you definitely want to add a pump saver chemical to the pump. If you do not take these 2 steps to "winterize" your pressure washer, you will absolutely ruin your machine.