The easiest way for me to do this is to just refer to experience.
You don't have to be getting 4000psi and 15L/m to get a great wash, but what you do get with this output is a consistent and quick finish, as shown in the video below:
In the past, I've used both petrol and electric pressure washers and I have my opinions on both of them.
It might be a telling sign that we do very little in the way of electric on ThePowerSite, but I will try and keep my opinions as unbiased as possible.
And for the sake of argument, during this blog, let's just consider petrol and diesel as the same thing. Cost is a different argument for a different post.
The way a lot of people, including ourselves like to list pressure washers for sale is in terms of either psi or bar, yet the consumer is almost always looking towards the flow rate as just as much of an important consideration.
Power is not always the be-all-and-end-all, as what most people really want is the ability to finish a job as quickly as possible. Obviously, to the best standard they can, but time is always a factor.
So, which one is more important?
Both are an important consideration, but the performance you get from your pressure washer will differ if there isn't a decent balance between the two figures.
But these are commercial pressures, not to mention larger machines, and probably slightly unsuited to most domestic locations when it comes to storage.
It's not something that everyone is going to want to purchase but given the chance, something that cleans like this is something everyone would want.
It's finding something that strikes the right balance and gets as much of the power and kick as the above machine, but into the most compact and cost-effective package as possible. This is regardless of petrol or electric here, as flow rate and pressure are relative to both.
The main consideration between the two of them is that to get to the same level of psi, you usually have to spend a lot more on electric.
Petrol engines drive a lot more pressure, so the size and eventually cost is reduced.
A good example of using an unbalanced washer in terms of flow rate and output was around about 18 months ago, where my father went and got himself an electric pressure washer.
It was a JCB PW6 model and I have no idea how much he paid for it and a quick internet search shows up nothing but there are blue Nilfisk models that look exactly the same as the PW6 model all around the £80-£112 mark for the same type of machine.
The JCB has a maximum output of 140 bar which is around the 2000psi mark. 2030psi to be precise. However, its flow rate is a maximum of 15L/m depending on which setting you had the machine on.
Now, these figures would be an output rating I would consider as unbalanced. Nevertheless, I borrowed it in the interests of fairness and gave it a go.
I wanted to wash a patio and a wooden fence. Just simple and basic that would and could apply to 99% of most domestic users. It was good on the patio. The brickwork came up almost instantly with no trouble at all. It took me around 10 mins to strip around 10 sq metres of patio of *almost* all blemishes and the results of just a minutes washing can be seen below.
However, it too much longer to get any joy with wood, and it wasn't the most joyful I'd ever felt before to be honest.
I live close to the sea and get a lot of algae build up on the wooden framing. It wasn't so effective on this and only took away small patches, even when spending the time to keep going back over the caked in areas.
The same for the wooden fence, but even at maximum output, the lower 2000psi output meant that the algae didn't budge an inch.
The end of the lance was also a problem. Its spray was pretty straight and although it did some with a few different attachments, none seemed to produce the fan effect I wanted to move the job along.
So, with this experience in mind, I'm always in the knowledge that flow rate isn't everything.
If you have a pressure washer with a very high flow rate but low psi output, then speed isn't going to count for much when the quality of the finish is not there. Nobody is interested in doing a bad job quickly. Though I suppose it's at least one step up from doing a bad job slowly.
Anything other than patio work and this type of washer was useless, and we have common complaints from lots people who want to do more than just patios and brickwork with their electric washers.
So, for those of you out there in the market for a pressure washer, take stock of what you are considering.
On the flip side, there is no point, especially if you're a commercial cleaner, where you have a huge pressure output with a low flow rate, as time is basically money, and you will need a lot more time to get the job done, though it will be done well at least.