How Do Robot Mowers Work?

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If you’ve ever seen a robot lawn mower in action, it’s normal to have the thought that maybe you accidentally stepped through a time portal and wound up in another dimension. There’s no one standing behind it?! How does it know when to turn around?! Why did it stop when it started raining?! 

How do these robot mowers work?

All of these are very legitimate questions, but the inner workings of a robot lawn mower aren’t all that complex. And once you understand a little bit better how they work, you’ll likely see why these machines are effective replacements for traditional lawn mowers. In fact, you may even want to get one yourself. 

After all, what could be better than sitting back and relaxing on Saturday afternoon instead of sweating on the mower? Not much, we say. Not much. 

Here’s everything you need to know about how automatic lawn mowers work.

Electric Motors and Batteries

The first thing you’ll notice about a robot lawn mower is that it’s pretty much silent. With the exception of a gentle whirring coming from the blades, these machines make pretty much no noise at all. 

This is because they run on electric motors that have rechargeable batteries. Not unlike the electric vehicles currently hitting the roads, such as the many Tesla models out there, robot mowers require no gas at all, and they also give off zero emissions, which is nice for the planet.

Of course, what this means is that you need to pay attention to the charge level of your mower’s battery. This is usually easy, though, since it does it itself. When it senses it has a low battery, it will return to its charging station, recharge, and then continue cutting when it’s got the battery to do so. 

One downside is that these batteries usually take several hours or more to charge. So, if you need to cut the grass and the battery is low, you’re pretty much out of luck. But this situation shouldn’t really ever happen if you let the mower do its thing.

Cutting Area

The size of the battery is ultimately what determines how big of a lawn the mower can cut. Manufacturers give estimates based on the size of the mower, the speed with which it travels, and also battery life. 

A mower that is rated to cut .5 acres is limited to a lawn of this size because after that amount of time it will need to return to the charging dock to recharge. So, it can technically cut larger lawns, but it wouldn’t be able to do it at the same time or even on the same day. 

Smaller Rotary Blades

The other thing you’ll likely notice about robot mowers, and that will make you wonder how they work, is that they are rather small. Usually not more than 10 or so pounds and a few feet square, these things hardly look like lawn equipment. 

Part of the reason for this is that it’s cheaper to make a smaller device. But because there is no internal combustion engine, manufacturers are also able to pack more punch into a smaller package. 

Of course, having a smaller device means using smaller blades. Most robot lawn mowers work with rotary blades, meaning they are circular. Many robot mowers have multiple blades to help them cut more area. 

The only real thing you need to be concerned about when it comes to the blades is how often they need to be changed. Because they are smaller, they tend to wear out more quickly. So, depending on how large your lawn is and how often you cut it, you may need to replace blades once every six months or so.

Boundary Wires and AI

When you watch automatic lawn mowers work, it’s somewhat frightening: they appear to be thinking as they move. 

In a sense, they are. But they aren’t quite thinking in the same way we as humans do. Instead, the mower is communicating, using radio signals, with the boundary wire you’ve installed around your property. This is quite literally a wire that runs around the edges of your lawn, and it tells the mower where it is on your property and where it should go next. 

After it’s mowed your lawn a few times, it will figure out the best route and keep doing that until something changes. For example, if you install a jungle gym in the mower’s path, it will likely have to make a new path when it mows. 

Some of the more sophisticated robot mowers work using artificial intelligence (AI). This software allows the mower’s computer to process in real time what is happening on your lawn, allowing it to make adjustments on the fly that will allow it to cut your lawn more effectively.

Installing the Boundary Wire

Worx Landroid M WR147

This boundary wire is something you must install yourself. But most manufacturers recommend you let them do it, since the way in which you install this wire will significantly impact your mower’s performance. 

Unfortunately, this is rarely included in the cost of your mower, so if you do go this route, expect to pay an additional $500 on top of what you spent on the mower. 

Why not use GPS? You might be asking. 

A valid question, especially since you have likely seen that some robot mowers, such as the Worx Landroid WR147, come equipped with GPS capabilities. But the issue with GPS is that it is still only accurate to within 10 feet or so. This is fine when you’re driving in a car, but when you’re dealing with the tight spaces on a lawn, ten feet can make a huge difference. 

Therefore, robot lawn mowers that do work with GPS usually use it to track the mower’s progress, or to locate it in the event it should get stolen or wander off to somewhere it shouldn’t be.


In addition to the sensors the robot mower uses to determine where it is on the property in relation to the boundary wire, most mowers now come with a range of other sensors. 

The most common is a rain or moisture sensor. All robot mowers work just fine in the rain and can get wet without getting damaged. But cutting wet grass is more work for the mower, and it’s also not great for your lawn. Plus, if you’re constantly cutting wet grass, clippings are going to get stuck in the undercarriage and this can hurt performance. 

Some robot lawn mowers, such as the Gardena Sileno, also come equipped with a frost sensor to make sure they do not cut your grass when it is frozen, for this can really harm your lawn.

Another feature you will find on most robot lawn mowers is some sort of anti-theft device. If the device is moved when it’s not supposed to be, or if it senses it is outside of its boundary area, then you will likely get a notification, often with GPS coordinates, so that you can go find your mower and bring it home.

The App

As with most things these days, what really makes robot lawn mowers work is the app that comes with it. Each manufacturer has its own mobile app that lets you set the mower’s schedule, change its settings, follow its progress, get maintenance updates, and even manually override it if you see it’s heading off track. 

These work because robot mowers come equipped with either Bluetooth or Wifi capability. Wifi is a bit better as it will allow you to do more from further away, but BLuetooh gets the job done. 

On some mowers, you can use the app to link your device to other smartphone gadgets, such as Amazon Alexa. This is the case with the Robomow RS360, which you can control using nothing more than your voice. 

Each app is a little different, and some are definitely better than others. But being able to control these mowers from the comfort of your home using nothing more than your phone is one of their big selling points and why they are seen as so convenient.

How Do Robot Lawn Mowers Work? Mystery Solved!

While your first thought might be that these machines use dark magic and wizardry to work, the reality is that there’s some pretty basic technology behind them, stuff that has been around for some time. It’s just now being made small and affordable enough to fit inside robot lawn mowers. 

So, now that you know how robot lawn mowers work, it’s time to ditch your gas-guzzling machine and make the switch. Take back your Saturday’s and never mow your lawn again!

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