What is the difference between PSI and GPM, and which matters more?

PSI (pounds per square inch) measures the force of the water stream, while GPM (gallons per minute) measures the volume of water flowing through it. Neither alone tells the full story, cleaning units, sometimes called CU, are roughly PSI multiplied by GPM, and give a better sense of overall cleaning power. A 2300 PSI, 2.3 GPM machine clears a wide surface faster than a 3000 PSI, 1.2 GPM machine, even though the second number looks more impressive.

Should I buy electric or gas?

Electric is the right choice for most homeowners: quieter, no fuel or oil maintenance, and lighter to store, with plenty of PSI and GPM for driveways, decks, cars, and general cleaning up to roughly 2300 PSI. Gas becomes worthwhile if you're regularly cleaning large properties, stripping heavy oil stains, or need to work somewhere without a nearby outlet, since gas units routinely deliver 2800 PSI and up with no cord-length limitation.

What nozzle do I need for my task?

A 0-degree pinpoint nozzle is the most aggressive and should be reserved for the toughest concrete stains, never used on wood, paint, or siding. A 15-degree nozzle handles general concrete cleaning. A 25-degree nozzle is a good all-purpose choice for siding, vehicles, and most outdoor furniture. A 40-degree wide fan is the gentlest option, best for wood decking, cars, and anything where surface damage is a concern. A dedicated soap nozzle applies detergent at low pressure.

Do I need a gas or electric pressure washer if I only clean once or twice a year?

Electric, in nearly every case. The maintenance-free convenience of an electric unit outweighs the extra PSI of a gas model for infrequent use, and a mid-range electric pressure washer in the 2000 to 2300 PSI range still clears most residential jobs comfortably within an hour or two.

How to Choose a Pressure Washer: A Complete Decision Framework

A step-by-step framework for choosing a pressure washer, covering PSI and GPM, electric versus gas, nozzle types, detergent systems, and how to match a machine to driveways, decks, cars, or small household jobs.

Step-by-Step Guide

Step 1: Define your primary use case

Decide what you'll clean most often, driveways and concrete, decks and wood, cars, or a mix of small household jobs. This determines the PSI range you actually need. Driveways generally want 1900 to 2300+ PSI, decks are safer in the 500 to 2000 PSI range depending on wood condition, and cars are safest around 1200 to 1900 PSI.

Step 2: Choose electric or gas

Pick electric if you have access to an outlet, want quieter operation, and your PSI needs top out around 2300. Pick gas if you need 2800+ PSI, work in areas without power access, or clean large properties regularly enough that the extra maintenance is worth the performance gain.

Step 3: Match PSI and GPM to your budget tier

Under $150 typically gets you 1500 to 2030 PSI at 1.2 to 1.76 GPM. Under $300 typically gets you 2000 to 2300 PSI with a more durable motor (water-cooled induction or brushless) and sometimes an adjustable wand. Gas units in the $300 to $400+ range deliver 2800 PSI and up.

Step 4: Check the nozzle and accessory kit

Confirm the unit includes at least a narrow nozzle for concrete, a wide fan nozzle for delicate surfaces, and a dedicated soap nozzle. If you plan to use a foam cannon or surface cleaner, check whether the fitting is a standard quick-connect (wider accessory compatibility) or a proprietary bayonet-style connector.

Step 5: Consider detergent tank design

A single onboard tank is fine for most users. Dual removable tanks, like on the Sun Joe SPX3000, let you keep two different detergents loaded at once, useful if you regularly switch between an all-purpose cleaner and a degreaser.

Step 6: Factor in storage and portability

A compact, lightweight unit like the Greenworks GPW1501 is worth prioritizing if storage space is tight or you'll be carrying it to different locations. A larger, wheeled unit is fine if it lives in a garage and mostly stays near the driveway.

Step 7: Review the warranty and motor type

Standard brushed motors are the norm in budget units and are fine for occasional use. Brushless motors (Greenworks Pro 2300 PSI) or water-cooled induction motors (Karcher K5 Premium) cost more but are built for longer service life under frequent use, and typically come with longer warranty coverage.

Choosing a pressure washer usually comes down to answering three questions in order: what will you mostly clean, how much do you want to spend, and how often will you actually use it.

Get those three answers first, and the rest of the decision, electric or gas, PSI range, nozzle kit, detergent system, mostly falls into place on its own.

This guide walks through that decision in order, starting with matching PSI to your primary task and ending with the smaller details, warranty length and motor type, that mostly matter for frequent, long-term use.

Most homeowners land somewhere in the 1900 to 2300 PSI electric range, and that's intentional, it's the sweet spot that covers driveways, decks, cars, and general cleaning without the maintenance of a gas engine.

Step 1: Match PSI to Your Main Task

Driveways and concrete: 1900 to 2300+ PSI. Set-in oil stains benefit from the higher end of this range or a gas unit.

Decks: 500 to 1500 PSI is the generally recommended safe range for softwood, with hardwood and composite tolerating up to 2000 PSI. Every pressure washer in this category exceeds that at full power, so nozzle choice and distance matter more than the machine's max rating.

Cars: 1200 to 1900 PSI, held at least 12 inches away with a wide fan nozzle, is the safe range for paint.

Small jobs (patio furniture, grills, bikes): 1200 to 1500 PSI is plenty, and a compact, lightweight unit is often more valuable here than extra PSI.

Step 2: Electric or Gas

Electric covers the large majority of homeowner needs. It's quieter, needs no fuel or oil, and tops out around 2300 PSI in the models covered in this category, plenty for driveways, decks, and cars.

Gas becomes the better choice for large properties, heavy annual oil stain removal, or working somewhere without outlet access. Expect 2800 PSI and up, along with the tradeoffs of fuel, oil checks, and louder operation.

Step 3: Budget Tier and What It Buys

Under $150: 1500 to 2030 PSI, standard brushed motors, plastic housings. Plenty of capability for routine seasonal use.

Under $300: 2000 to 2300 PSI, more durable motor designs (water-cooled induction or brushless), sometimes an adjustable wand. Worth it for frequent, multi-year use.

$300+ (often gas): 2800 PSI and up, built for heavier and more frequent cleaning demands.

Step 4: Nozzles and Fittings

A useful accessory kit includes at minimum a 15-degree nozzle for concrete, a 40-degree wide fan for delicate surfaces, and a soap nozzle for detergent application. Check whether the unit uses a standard quick-connect fitting or a proprietary bayonet-style connector if you plan to add a foam cannon or surface cleaner later.

Step 5: Detergent System

A single onboard tank is sufficient for most buyers. Dual removable tanks are a genuine convenience if you regularly switch between an all-purpose cleaner and a dedicated degreaser for stains.

Step 6: Storage and Portability

If storage space is limited or you need to move the unit between locations, prioritize a compact, lightweight design over extra PSI you likely won't use safely on most home surfaces anyway.

Step 7: Motor Type and Warranty

Standard brushed motors are fine for occasional use. Brushless or water-cooled induction motors cost more upfront but are built for a longer service life and typically ship with a longer warranty, worth it if you'll use the washer regularly for years.