Gas Versus Electric Power Pressure Washers
PSI, GPM and Choosing From Karcher, Husky, Excell, McCulloch etc
Apr 18, 2009
Cleaning with pressure washers (power washers) uses less water than cleaning with a garden hose. And the high water pressure means that chemicals can be reduced or avoided entirely. Scrubbing is also reduced or eliminated.
Pressure washers are used to clean
- decks
- driveways
- cars, motorcycles, boats
They can blast away moss, mold, grease and other dirt. The more powerful models can strip paint off. Popular brands include Karcher, Husky, Excell and McCulloch.
How Much Power or Water Pressure (PSI) is Enough?
The main question when choosing a pressure washer is, How much power is enough?
The force of the water jet depends on
- the pressure generated by the pump
- the volume of water pumped
- the width of the water jet (narrowing the jet reduces flow rate but increases pressure)
- the distance between the nozzle and the surface being cleaned
This means that by using a narrow water jet, even less powerful pressure washers can develop a lot of cleaning power. The trade off is that a narrow jet means a longer cleaning time.
It is therefore difficult to come up with a number and say that pressure washers below this rating are not powerful enough.
The most demanding application for a pressure washer is to strip paint. The actual water force needed to strip paint depends on the material painted and the type and age of the paint. A specific number also cannot be given.
For comparison
- Average garden hose pressure is 50 PSI (Pounds per Square Inch) but can vary from 25 to 100 PSI.
- Electric pressure washers vary from 1300 to 1800 PSI, at about 1.4 GPM (Gallons Per Minute).
- Gas pressure washers vary from 2000 to 4000 PSI, at about 2.5 GPM.
Roughly speaking, 1800 PSI is enough to damage wood, bricks and cut human skin.
Electric Pressure Washers
An electric motor is used to drive a water pump. Like many electrical power tools, maximum power is limited by the current capacity of household power systems (13 to 15 amps). Heavy gauge (12 gauge) extension cords should be used to avoid overheating the cord and the motor.
Mixing water and high voltage in one machine is obviously dangerous. Some pressure washers therefore come with a GFCI (also known as ELCB) circuit breaker to protect against electrocution. If not provided with the pressure washer, a generic plug-in GFCI unit can be purchased separately.
Advantages
- Low maintenance.
- Relatively quiet.
- Relatively light.
- Can be used indoors.
Disadvantages
- Power cord is inconvenient.
- Limited power.
Gas Pressure Washers
Gas pressure washers can be thought of as a gas mower, but with a water pump instead of a rotating blade. They are significantly more powerful than electric models.
Advantages
- Powerful.
- Mobile. Not tied down to an electrical power point.
Disadvantages
- Water jet can be powerful enough to be dangerous.
- Cannot be used indoors because of exhaust fumes.
- Gas engine can be difficult to start.
- Gas engine needs more maintenance than an electric motor (engine oil, spark plugs, choke, draining the engine).
- Noisy.
- Heavy.
The Best Power Washer
For most homeowners, the convenience of electric pressure washers will outweigh their limited power. Even 1500 PSI will be enough for most jobs. For the rare occasions when more power is needed, a gas pressure washer can be rented.
Reliability can be an issue with power washers. The high pressures generated means that the motor, pump and other components are under high stress. It is important to check warranty terms and conditions, and to search the Internet for user reviews before purchasing.
Steam cleaners can be better for some jobs.
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