Variable fan-jet: also called variable pressure lances, these allow you to vary the force of the jet from a focused point to a broad fan. Buying a new pressure washer can be confusing. There are usually several models in each manufacturer's range, with different types of motors and impenetrable model numbers which mean that useful accessories are either included in the price, or have to be bought as an extra.

Pressure gauge: some more expensive models have a pressure gauge on the lance handle but, as the pump pressure doesn't vary, they're of little practical use. Our in-house experts at the GHI assessed the pressure washers' performance on common outdoor cleaning tasks, using their high-power jet sprays to take on muddy patios, windows and cars. The testers noted how easy the pressure washer was to set up, use, manoeuvre and, of course, the time it took to get the job done. Basic machines come with one lance – a long tube with a nozzle at the end. A fixed lance can’t be adjusted, though you can move it nearer or further away from the area you’re trying to clean. You can also buy models with a variable pressure lance, where you can twist the nozzle at the end to alter the power of the spray – rather like a hosepipe attachment. This lets you create either a powerful narrow jet of water or a gentler, broad spray. As a result, I left the patio roof looking like an unfinished job. Again, that’s not a problem that’s exclusive to the Mac Allister 1,800W, but if you’re looking to buy a pressure washer for the purpose of cleaning your conservatory roof, you might want to reconsider. Mac Allister 1,800W review: VerdictHaving recently cleaned my patio while testing the Kärcher K4 Full Control, I decided to put the Mac Allister through its paces by cleaning my car, my wheelie bin and my conservatory roof. Karcher were the first to introduce smart technology to pressure washers so you can connect them to your smartphone via an app. Fewer owners of Karcher pressure washers experienced faults within the first seven years of owning it - 8% said they had (sample size: 2,271) versus 16% of Nilfisk owners (sample size: 185). Best for: Cleaning extensive areas of paving, grimy 4-wheel drive vehicles, commercial vehicles and caravans Thanks to their concentrated water jets, pressure washers will save you valuable hours on the most heavy-duty tasks, as well as being incredibly satisfying to use on dirt and grime.

For the money, the Mac Allister 1,800W is undeniably a powerful machine. Having also tried out the more-expensive Kärcher K4 Full Control, I’d say the two machines blast away dirt with similar gusto.This all depends on how much you can afford and how powerful and durable you want your pressure washer to be. Electric pressure washers are more suited to domestic cleaning, while petrol pressure washers are designed for professional, large-scale jobs. Best for: Cleaning small areas of lightly soiled paving, bicycles, small cars and garden furniture. If you just need a pressure washer for light cleaning, then most no-frills machines come with just one lance, which is a long tube with a nozzle on the end. The nozzle will usually provide variable pressure – when you twist the nozzle, you can adjust the spray from a powerful narrow jet to a more broad gentle fan. Additional handles: some machines have a variety of handles that will make carrying it around while cleaning much easier.