What is a robot lawn mower?
The growing trend of household appliances that take the hassle out of everyday chores has extended to the garden with robot lawn mowers. They work in much the same way as that clean up messy floors without any input from the owner, but robot mowers take care of your lawn.
With some models capable of 5,000sq m plots or more, robot mowers are a viable alternative to ride-on mowers for anyone with a lot of ground to cover who doesn't want the bother of mowing themselves. They also appeal to anyone wanting a no-fuss way of keeping their garden looking neat and tidy, and to less-able gardeners who may struggle to push around a heavy mower.
You'll need to pay a premium for the luxury of having an robot mower cut the grass while you recline on a Sunday afternoon, though. Robot mowers are expensive, with many costing significantly more than even the priciest conventional mowers.
How do robot lawn mowers work?
Once set up, robot mowers can be completely autonomous. There's usually no need to switch them on or keep an eye on them and, of course, there's no pushing required. The mower can come on at times scheduled by you, cut your grass and return to its dock to charge its battery ready for the next cut.
Many work by creating a map of your lawn to make sure they don't go over the edges into your borders. When they cut, most do so in a random pattern and it may look as though your mower has gone haywire, but good ones won't stop until they have cut every square inch of your lawn. Some do cut in methodical straight lines, though.
Most have sensors, so they'll stop if they encounter any obstacles and continue cutting in a different direction. So it's best to remove any large obstacles, such as children's toys and garden tools, but odd-shaped lawns or bushes and trees planted throughout your garden shouldn't be an issue for a good robot mower.
There's no need to empty them either. Rather than collecting the cuttings, the mower cuts them up finely and leaves them on the lawn as mulch to encourage healthy grass and help prevent weeds.
How to set up robot lawn mower
Assuming that you don't have any issues down the line, setting up your robot lawn mower could be the first and last time you interact with it. Most of the set-up is done on the device itself, or a smartphone app, but there is a more fiddly hoop you need to jump through.
Before you let your robot mower loose on your garden, you need to lay a perimeter wire so the mower can detect the boundaries. The wire also helps orientate the mower and guide it back to the charging dock. The wire is secured by pegs and is fairly inconspicuous, but some manufacturers and dealers will even lay the wire underground if you want it to be fully invisible.
The wire connects to the charging dock, which requires mains power, so make sure you set it up within reach of an outlet. Some manufacturers and dealers will install the wire and charging dock for you.
Once your wire is down you can start programming your mower. Generally, this will mean setting the date, time and how often you want it to cut the grass. There are some smart mowers that connect with an app on your smartphone, too. You can use the app to control the mower if you think the lawn needs an ad hoc trim, otherwise you'd need to use the controls on the mower itself.
What to consider when you're buying a robot lawn mower
How big is your garden?
Every robot mower has a maximum lawn size that it can cut. This is usually measured in square metres. Don't assume that a mower that covers less distance, or has less battery life, can do your entire garden in two trips. The mower may not come with enough perimeter wire to cover a bigger garden or it may not be able to travel far enough from its dock.
Are there any slopes in your garden?
Most robot mowers can handle a bit of a hill, but some can manage steeper inclines better than others. If your garden has any slopes then make sure the mower you choose has the power to get up them and keep cutting as it goes. You'll find the maximum gradient each mower can navigate in our .
Do you need a mower that functions in rain?
If your garden gets a lot of rain, then it may be worth investing in a mower that can cut grass in wet conditions. Some mowers struggle to cut wet grass, while others return to their dock automatically when the rain starts falling.
Some smart robot mowers are tuned in to weather tracking to optimise cutting at the best conditions. The , for example, uses a weather tracking system to cancel the usual cycle if the weather is too bad at the scheduled time for it to cut well.
Do you need a mower than can handle multiple zones?
If your lawn is separated by fences of paths then you may need to buy a multi-zone mower. This is also useful if you'd like your mower to do the front lawn as well as the back. Some models ask you set a base zone, which is mowed automatically to the schedule, while the numbered zones require you to manually start the mower and tell it which area to cut. If the mower can't access one of your areas, then you'll need to carry or wheel it there yourself.
Does it have fixed or pivoting blades?
Both types should be more than capable of cutting grass, but they aren't equal if they come into contact with something harder. Pivoting blades can move if they come spin up against any hard objects whereas fixed blades don't, meaning they are more likely to get stuck on anything solid in your garden, such as toys.
What's the battery life like?
Generally, the larger mowers that cover more ground also have the largest batteries, but machines designed for a smaller garden should be able to trim the whole thing on one charge. If you've got a multi-zone mower than it may need to charge between areas. Some mowers can charge to full in 45 minutes while others take a whopping 16 hours, so you may need to wait more than half a day before your mower can finish all of your zones.
It's very important to note, however, that you rarely get an exact measurable battery life from a robot mower as it uses a variable amount of power each time it runs. It mostly depends on the size of the area it's cutting, how much effort it needs to cut the grass, and the conditions.
In our lab tests, we measure the run time and charging time over a period of a month's cutting on various grass types and conditions to work out an accurate average run time.
Which brands are making robot lawn mowers?
Some of the biggest brands in lawn mowers are turning their hand to robot models while others have yet to release any.
Bosch's range of robot lawn mowers includes the and the . Both models are similar, but the 400 can handle lawns up to 400sq m, while the M+ 700 has a maximum lawn size of 700sq m - hence their names. They also both have an app that let's you control and monitor your mower remotely.
Bosch mowers are some of the only models that cut the grass in parallel lines. Although they won't leave stripes, this way of mowing reduces lawn stress.
Both mowers have adjustable blades, so you can have grass as short as 30mm and as long as 50mm, but they don't have as many cutting-height settings as other robots.
With eight different mowers, Robomow has a comprehensive range that covers relatively low-cost models suitable for modest lawns all the way to expensive machines that can mow almost an entire football pitch.
The RX range has two models designed for smaller gardens up to 300sq m, although the cheaper of the two, the RX12U, doesn't have a mowing schedule so you'll need to use the menu on the mower when you want it to start cutting the grass.
The RC range includes three models which can mow gardens up to 2,000sq m and the RS range can cover more than an acre of ground.
Prices range from £599 for the entry-level RC all the way to £2,999 for the top-of-the-range RS model. The RC range costs between £1,199 and £1,899.
Flymo's robots are cheaper than most at around £500-£600.
Husqvarna's premium X-Line range includes GPS-assisted navigation and theft tracking, headlights, and the 'Automower Connect' app, which enables tracking and control from a smartphone or as an integrated part of a smart home setup.
John Deere only offers one robot mower, the Tango E5 Series II. This heavy-duty robot mower looks robust and bulky. It costs more than £1,500 and, for the money, you'll get a mower that can cut grass come rain or shine and scale inclines of up to 36%.
As you might expect, given the price, the E5 Series II can mow a large plot. 2,200sq m is the maximum size and John Deere says it can run for 90 minutes on a single charge.
Stihl's range of iMow robot lawn mowers includes two series, the RMI 422 series and the RMI 632 series. Each have several models available, and the differences between them are mostly down to their cutting range and prices.
Depending on which model you choose, your robot could cut lawns up to 5,000sq m and cost anything from £999 up to more than £2,000. Bear in mind though that not all models are compatible with the iMow app, and they don't all come with installation kits, either. Make sure to check both of these things before buying.
There are five robot lawn mowers in Honda's Miimo range. There are three Miimo options which have maximum ranges of 1,500sq m, 3,000sq m and 4,000sq m, and all come with zone management so you can make sure every patch in a large garden gets cut, even if they're in separate areas.
The Miimo HRM models are all about smart technology - both the HRM 40 and the HRM 40 Live map your garden, and the HRM 40 Live can be programmed with your smartphone and voice-assisted with Amazon Alexa. They're both designed for smaller lawns up to 400sq m, though.
Worx's Landroid robot mowers among the cheaper options around. The robots with the largest cutting ranges still cost more than £1,000, but the cheapest model, the Landroid S300 WR130E, can be picked up for a little over £500.
Worx's robots have 'Cut to Edge' design, that has slots on the side that allow the mower to catch grass along the edges of your lawn and reach the blades close to walls. The 20V lithium-ion batteries are cheaply replaceable at £40, too, and the batteries can be used with other cordless gardening tools from Worx.
Mac Allister is known for its cheap gardening tools, and when it comes to robot mowers its no exception.
The cheap price does mean it compromises on some features - there's no smartphone app and the programming is more basic - but you'll still have the convenience of having your lawn cut for you.
How much should you pay for a robot lawn mower?
You can pay a small fortune for a robot lawn mower, but depending on the size of your garden you may not need to. The pricier mowers, which can cost upwards of £2,500, can cover huge surface areas of 5,000sq m or more whereas cheaper models, which you can buy for around £600 or even less, can manage lawns of around 400sq m, which is about the size of one and a half tennis courts.
Consider which features you need, such as the ability to tackle slopes or to control the robot mower from your smartphone, as these will help dictate your budget.