How to choose a robot lawn mower

Robot lawn mower

Mowing the lawn is an unloved tradition of summer. The old two-stroke won’t start without a full tear-down and rebuild. The kids refuse to help. You battle the grass catcher at every moment. Everybody but you cuts the grass wrong. But you can’t deny the pleasure of a neatly kept lawn… what to do?

Fortunately, there is a solution: A robot lawn mower. After all, robot vacuum cleaners keep the inside of your house tidy these days, so why not a similar device for the lawn?

Indeed, a robot lawn mower is very similar to a robot vacuum in many ways. It uses intelligent sensors to make sure it’s covered the whole lawn, it can detect when it bumps into something and change direction, and recharges itself at a base station.

And robot mowers are electric, too. So, they’re quieter than a traditional mower, you don’t need to mess about with oil and petrol (not to mention dodgy spark plugs and clogged lines!), and while the mower is doing its duty, all you can smell is fresh-cut grass.

There are a few caveats, though. A robot mower will set you back $800 and up, and it requires you to surround your lawn with a perimeter wire, so there’s a bit of set up work to do.

MoeBot S5
Robot mowers map then trim your lawn so you don’t have to, and recharge automatically when finished. Pictured: MoeBot S5

Consider these before buying a robot lawn mower

  • Size of lawn and mower battery life
  • Gradient / slope of lawn areas
  • Number of lawn areas
  • Location of charging station
  • Outdoor Wi-Fi coverage (if using app control)
  • Mower safety and security features

How a robot lawn mower works

Like a robot vacuum, a robot mower is a flattish, wheeled robot that trundles around an open space until its internal mapping system says the whole area has been covered.

Inside, the vacuum has the advantage of walls to show where the carpet ends. Out on the lawn, the robot mower relies on you installing a conductive wire around the whole perimeter of the lawn (or lawns) you want the robot to cut.

Landroid Worx WR140
Robot mowers cut close, but some manual edge trimming may still be necessary. Pictured: Landroid Worx WR140

The wire usually comes wrapped in green insulation so it won’t stand out, and it goes flat against the ground, held down with pegs. When the mower reaches the wire, a sensor underneath detects it, and the mower knows to turn away from the edge of the lawn.

Some robot mowers can run slightly over the wire, so the lawn is cut right up to the wire itself. Others turn a little before the wire, or have offset blades that cut close to edges. In all cases, edges such as retaining walls, pathways and raised garden beds will still need the whipper-snipper treatment from you (or a willing gardening partner!) to give your lawn the fully manicured look.

The size of lawn the robot mower can cover depends on the battery capacity of the model you choose. A cheaper robot mower should be able to handle 600 square metres of lawn, while the top-of-the-range models (costing over $5000) can munch down 5000 square metres – about 1.1 acres.

When the battery runs low, the robot mower returns to a charging station, which must be positioned somewhere on the lawn’s perimeter (ideally in a sheltered location). This station also needs access to an outdoor power point.

The price of a robot lawn mower can range from as little as $800 all the way up to $5000 or $6000

Ambrogio L400
For large-area luxury lawns, commercial grade robot mowers can cost more than $20,000. Pictured: Ambrogio L400

All robot mowers have on-board controls, usually with a small LCD screen, that lets you set mowing schedules, and see the battery status. Many now also include connectivity to a mobile device (phone or tablet) via Wi-Fi or Bluetooth, so you can control and schedule the robot mower with an app.

As mentioned, the price of a robot lawn mower can range from as little as $800 all the way up to $5000 or $6000. Battery capacity and ‘smarts’ (ability to ‘remember’ multiple lawn layouts, for instance) account for most of the difference in cost, and for palatial grounds, commercial-grade models with racing car looks can set you back more than $20,000.

All these mowers are what’s called ‘mulching’ mowers, which means they don’t have a grass catcher for you to fight with. Instead, the robot mower cuts the grass into small pieces and directs it back down into the lawn, thus feeding it back to itself.

What makes a good robot lawn mower?

There are a few key features to look for when choosing your robot mower, which will make it more versatile across your whole property. The last thing you want is to buy a mower that can only cut one part of your lawn!

Gradient, safety and security

A good robot mower should be able to handle 600-1400 square metres of lawn, and crucially be able to operate on a slope. Some models can handle up to 30 degrees of tilt, and if they lose grip or start to tumble, they will sound an alarm and switch off automatically.

Safety is obviously a key issue for a robot equipped with spinning blades, so robot mowers have bump sensors and proximity sensors that will make them stop if they encounter something on ‘their’ lawn (the area inside the perimeter wire). Those with rain sensors will return to charge during a downpour, rather than try to cut wet grass.

When it comes to curious kiddies and boisterous pets, the robot mower’s tilt sensor will also stop the blades if the mower is lifted or tilted up away from the ground (such as by a child looking to see how the magic works).

Most models also include a big red or black ‘STOP’ button on the back of the mower, within easy reach of your foot. Just run up and stomp the robot to make it stop!

And to protect your investment, most mowers will come with some anti-theft features, from basic PIN code locks to alarms and, in higher end models, GPS tracking via the mower’s app.

Number of blades

Another sign of a good robot mower is the blade system it uses. As a mulching mower, a robot mower relies on multiple very sharp, almost razor-like blades, rather than the traditional two-bladed rotors of a two-stroke pushie.

Generally, the smaller the blades the better. Look for units that have nine-blade systems, especially if your lawn is one of the tougher grasses.

Something to note about robot mowers generally is that they are a ‘maintenance’ mower, which relies on being able to cut the grass short, and often. They don’t have the torque of a four-stroke ride-on to let them plough into great thickets of long-neglected lawn. If your lawn gets seriously overgrown, you’ll need to have it cut short before the robot mower can start its weekly duties.

How do I install a robot lawn mower?

Robot lawn mowers do require a bit of lawn set up before they can get to work. First up, your lawn needs to be fairly even – it’s okay if there’s a bit of a slope, but lumps and bumps and especially divots and holes, can be problematic for the robot mower.

Each time you want to mow, you’ll also need to pick up anything on the lawn. Since the robot mower is electric, and very low to the ground (for mulching), you need to be extra vigilant about small rocks, chunky twigs, and overgrown matchbox cars (those things are metal!).

Setting up perimeter wire

As we’ve mentioned, the key to a robot mower being able to cover a whole lawn is the perimeter wire. This needs to be carefully installed and pegged down, so it lays absolutely flat. If there are any undulations or kinks in the wire, the robot mower might chop it, and that’s a pain.

Some retailers will include installation as an extra (or even as part of bundle deal), which can be worth taking advantage of, as the rep will not only install your perimeter wire properly, they’ll also give you training on all the robot mower’s functions – including how to spot when it needs maintenance, and how to troubleshoot common problems.

Charging the robot mower

As part of the perimeter wire, you need to choose a spot for the charging shelter, or base station. Some models come with a weatherproof charger (that also works as a shelter for the robot mower) but it’s best to have this in a sheltered location out of the worst of the weather. It does need to connect to an outdoor power point, so this might limit where you can place it in your garden.

Moebot S5
Install charging stations undercover, near mains power and with 2m in front for the mower to manoeuvre in to place. Pictured: Moebot S5

The charger will need quite a bit of space around it for the robot to shimmy its way in for a battery top-up. Typically, this is two metres in front of the charger, and a metre either side. Check the documentation that comes with your robot mower for the exact space you’ll need.

After all the hardware is installed (and while the robot mower is getting a charge) you can use the onboard controls to set up a mowing schedule, and set the blade height. If your robot mower has connectivity features, you can download the relevant app from your mobile device’s app store, and connect to the mower remotely.

Control with an app

The app may also have functionality to let you schedule mowing while you’re away from the property, too. For this to work, your mower will need to have a Wi-Fi signal and connection to your home internet.   

Once the robot mower is charged, you can use the controls (or app) to mow immediately, and watch as the robot mower maps its way around the lawn. If the lawn is bigger than the battery can handle, the robot mower will return to the charger, get a top up, and then continue where it left off until the job is done.

A reminder: if your lawn is quite long when you get your robot mower, you may need to do one more manual mow with your existing lawnmower, to bring the grass down to a height the robot mower can handle. The documentation for your robot mower will tell you the maximum grass length your model can cut.

Like a traditional mower, it is possible to adjust the cut height with a robot mower. These controls are usually mechanical, on the robot mower itself, but some higher-end models even let you set cutting height from the app too!

What if I have multiple lawns?

Robot mower
Robot mowers can cut multiple lawn areas and include height adjustment options to control the closeness of the cut.

Of course, not everyone has a square house in the middle of a flat square lawn – some people are cursed with half a dozen lawns, and dragging a push-mower from lawn to lawn makes a mockery of summer fun.

Robot mowers can handle multiple lawns, and higher-end models can remember multiple ‘maps’ which allows them to cut the lawns more quickly (by limiting how often they drive over the same place twice).

Each lawn will need its own perimeter wire, and some models need a charging station on each lawn too. But all you need to do is carry the robot mower from one lawn to the next, and press go.

What maintenance does a robot lawn mower need?

Compared to a petrol mower, robot lawn mowers require very little maintenance. You probably won’t need to clean the wheels and underside of stuck grass after every mow, but it’s a good idea to give the robot mower a quick check once a week, and clear out any grass with a brush.

The blades on a robot mower are different to a traditional mower, in that they are smaller and more like razors. They can be easily removed and replaced. Some models have blades that can be resharpened or flipped when one side gets blunt, but generally the idea is to completely replace them with a pack of new ones all at once, to keep the cut even.

The battery will last up to two years with regular use, and the robot mower’s onboard controls (or the app, for those with that feature) will let you know if it’s time to replace the battery. This is usually as easy as removing a couple of screws, pulling the battery unit, and slotting in a new one.

Robot mower
Many robot mowers include anti-theft features, such as PIN code locks and alarms. Pictured: Moebot S5

You can order replacement parts online, or do a web search for a nearby business that offers robot mower servicing. More and more traditional gardening hardware stores are starting to sell and support robot mowers, and some will service a robot mower for you too – expect to pay around $100+ to get blades replaced/sharpened (depending on model) and everything checked and cleaned.

If you need a new battery, that will cost extra – again this depends on your particular model of robot mower. Cheaper robot mowers have cheaper batteries, from $80 all the way up to $500+ for a battery that can do the full acre.

Robot mowers usually come with a standard warranty of two years, plus another year on top as an extended (paid) warranty. 

Learn more about robot mowers in GadgetGuy news and reviews.

Robot My Life
Starting from $950 the MoeBot range of robot mowers deliver a healthy great looking lawn and free you from the chore of weekly mowing.