How do you determine what size of pressure washer to use?

There are three major factors that compare and resolve the pressure washers selection size:

Difficulty of the cleaning job: Depending on how difficult it is to powerwash the dirt from an object or surface and also depending on what type of dirt is being removed, you should determine the size of the machine. If you use a cart pressure washer to powerwash a car/boat wash, or maybe for patio cleaning, purchase a small to medium size powerwasher, But, if you use it to remove oil, grease and fuel spills, then you will need a large hot high power washer.
Frequency of use: If you plan to pressurewash and use equipment frequently, you should choose one with high ratings in order to increase efficiency and minimize time. Smaller washers are suitable for short and less frequent jobs. Larger washers are right for bigger jobs with frequent use. If you plan to use the powerwasher for less then 20hrs/year you will need a residential size unit. If you plan to use it around 30hrs/week you need to consider a commercial pressurewasher. Finally, if you know that you will be using it for 40hrs/week or more you will need to invest in a heavy duty industrial pressure washer.
Cost: Machines with greater PSI and GPM are costlier. In addition, hot water pressurewashers are more sophisticated and more expensive than the cold-water pressure washers. Some cleaning jobs require plenty of water and very little pressure (example: in fiberglass manufacturing), and some require a very high pressure and less water (driveway/parking lot pressurewashing). Depending on the type of the job you will be performing you have to make a decision what washer is most suitable for completing the job most effectively.

Not sure if you need a cold or a hot water pressure washer?

Once you know what applications you will be performing with your power washer you will be able to decide what type of unit you will need to purchase. Here is the general guideline for what the cold and hot water units are considered to be best for:

Cold Water Power Washers

Cold water units are best suitable for car, deck, grill, patio, sidewalk, house, bus, and truck power cleaning. Also, if you have a car washing or an airplane pressurewash business cold water power washers are the most fitting machines for it.

Hot Water Powerwashers

On the other hand, hot water pressure models are excellent for oil, grease, and fuel spills, and for sanitation. Hot water pressurewashers are also the best candidates for places such as garages, industrial plants, agriculture machineries, service areas, food processing plants, and airport environments.