Why are gasoline powered pressure washers more powerful than electric?

The Gist:

Electric powered equipment (for around your home) is limited by the amount of electricity it can draw from your wall outlet (or its battery). If there was more available electricity, like at a manufacturing plant, then it could power bigger electric motors powering bigger pumps, alternators etc.
Gas powered engines (especially in home-use power equipment) are only limited by size/cost.

The Full Story:

We seem to all know instinctively that when it comes to portable power like pressure washers and lawn mowers – gasoline engines are more powerful than electric ones.

But why?

After all, much of heavy industry chooses electric motors (not gas engines) to power conveyor belts, saw mills, ore reclaimers and more.

What’s the deal when it comes to portable machines?

Home-use electricity limitations

In residential power equipment electric machines are limited by the electricity available to them from your home wall outlet or from their battery.
Your home has a breaker in the electric distribution board that will blow if you try to draw excess current.

Gas powered limitations

Gasoline engines burn gasoline for energy and there is no breaker to blow.
Gasoline fuel has more energy per mass than batteries.
To provide more power a gas engine just needs a bigger combustion chamber volume.
In other words: You can have large gas powered appliances around your home by having bigger gas engines – look at your car in your garage.

Can you make an electric pressure washer as powerful as a gas powered one?

Yes.
If you design a pressure washer with a larger electric motor and you plug it in to a much higher current connection (like at a mining site or manufacturing plant) then you can have a much more powerful pressure washer – as or more powerful than gas.
Heavy industry has much higher load electricity distribution networks than your home… I’ve personally used electric pressure washers with 5,000 PSI and 4.5 GPM. It was at a rendering plant. The electric motor was a 3-phase induction, 460 V, 20 HP, capable of drawing 47-amps (a typical home allows for 12 – 15-amps).
Heavy industry needs this capability to draw enough electricity to power heavy duty electric motors for moving 1,000-foot long conveyor belts and other high power requirement processes.

Comparison of gas vs. electric power (Watts and horsepower) in residential power equipment

To put some numbers to it: Electric pressure washers can have about 1.5 hp once you account for inefficiencies… You can draw 12 – 15 Amps from your home outlet. 12A at 120V is 1440 Watts or 1.93 hp.
Small gas engines in pressure washers are 3 – 4 hp. The Honda GX160 engine used in several of the top 10 bestselling gas pressure washers has a power output of 2.7 – 4.7 hp at 2000 – 3600 rpm.