Gas or Electric?
Choosing the right pressure washer for your foam cannon is important to ensure you are getting the expected thickness of foam. Generally speaking, gas powered pressure washers result in thicker foam in comparison to electric powered alternatives. The right GPM flow should give you thick foam, regardless of how the pressure washer is powered. Electric power washers are a popular choice because they are much more quieter. Both however, can be used to wash vehicles with a foam cannon.
How many PSI or GPM?
The real metric to pay attention to is the GPM output of the pressure washer. The higher the GPM value, the thicker foam you will get. 1.75 GPM is usually enough to output thick foam. Pressure washers with a lower GPM rating will work; the foam will be more of a liquid consistency. Nonetheless, it will be equally effective in denominating the surface for washing.