One of the first considerations would be whether the unit is powered by gas or electric. The electric models are generally going to be lighter to carry, are inexpensive and are perfectly capable of smaller cleaning jobs around the home such as washing a car or cleaning off patio furniture. Gas powered models are going to be more powerful than the electric version and will obviously not require power from an electrical outlet. This means that they can be more portable and taken into areas such as a job site that does not have power. Gas powered models will be generally more durable and will clean things in less time and take less effort. Due to fumes, gas pressure washers should always be operated outside. The pressure rating of the unit should be considered as well. For the average homeowner, this unit would be utilised for things such as washing siding, washing the car or cleaning off a deck. A unit that is rated at 1,500 to 2,000 PSI should be sufficient. If needing to clean off concrete or driveways, having a washer with at least 3,000 PSI is recommended. If utilising this for commercial or industrial use, the model should have at least 3,000 PSI. In addition to the pressure, the amount of flow is important. If cleaning an area that requires dirt to be pushed quite a distance, a high flow model should be purchased. Pressure washers will come in either hot or cold water models. For most average cleaning jobs, a cold water device will be sufficient. It is also easiest to get cold water as all outside spigots will contain cold water. A hot water model will be able to clean more efficiently. These are generally necessary when grease needs to be cleaned up. Hot water models will generally have an additional heating element to bring the water up to temperature. This will add additional cost to the unit. The brand of the engine as well as the pump should not be overlooked. Generally, it is going to be used quite hard and the pump and engine need to be able to withstand many hours of continuous use. It is usually best to stick with brand name models. If the company that manufactures the engine and pump are unknown, these may be made with inferior parts and may not provide the same level of performance as the major brands will. It is always a good idea to do research on the different companies before choosing a particular unit.