slope and hill performance of robot lawn mowers

Slope And Hill Performance Of Robot Lawn Mowers

Robot lawn mowers can be a great option for labour free lawn maintenance, but what if your garden has lots of hills? Will a robot lawn mower be able to manage to climb steep slopes and hills to ensure that your whole lawn looks great.

Generally, slope and hill performance of robot lawn mowers is very good, but there is considerable variation between individual models and between manufacturers.

Cheaper models generally have less slope performance than more expensive models, but this is not universally the case. Some entry level models, such as the Worx Landroid S WR105SI being able to handle some of the steepest slopes at a very reasonable price. 

I think that slope and hill performance of robot lawn mowers is one of the more important things to research before considering a purchase. It would be very frustrating to get a new robot lawn mower installed, only to find that it was unable to cut part of your lawn due to the slope of your garden?

Slopes come in all shapes and sizes and it has been a goal in the development of robot lawn mowers to have versatility, to be able to handle most shapes and gradients of lawns. Your lawn may be hilly all over or may have one or more short, steep slopes.

Generally speaking, it will only be the very steepest slopes that you will need to look at carefully to ensure that your robot lawn mower will be able to handle this.

This article explains the features that robot lawn mowers have which help to make them ideal for working on slopes. It also discusses ways that you can reduce the impact of slopes and even ways to avoid this problem completely. 

How To Calculate The Slope Of Your Garden

When looking at your own lawn, it may be difficult to determine whether you need to worry about the slopes, or whether a robot lawn mower will handle your garden with ease. Thankfully, it is quite simple to calculate the slope of your lawn and I have written a guide explaining exactly how to do this.

Features Of Robot Lawn Mowers That Ensure Good Slope And Hill Performance

Wheel Design

Robot lawn mowers rely on large wheels with deep treads to give them the traction they need on steep slopes. The motors also turn the wheels slowly to avoid loss of traction. I normally find that the wheels on robot lawn mowers do a very good job of keeping a grip on my grass, even on steep slopes. There are a few scenarios where the performance will suffer however.

Firstly, wet weather can cause your grass to be more slippy, which will negatively impact the amount of traction the wheels can get. If you experience a very wet period, or, particularly in late autumn or early spring, your grass may be very soft or muddy.

In these situations, you may see performance suffer, but it should still get the job done, as long as you have bought a robot lawn mower that is rated to deal with the maximum slope in your lawn.

Secondly, over time, the wheels will pick up significant dirt and grass clippings in the treads of the wheels. These will reduce the depth of the treads and reduce the traction of the wheels on the ground.

This is much more likely to happen in wet or muddy conditions, but will happen to a lesser degree in all conditions. For this reason, to ensure that slope performance of your robot lawn mower remains as good as possible, you should clean the treads of the wheels every few weeks. I would advise to do this more frequently in wet weather, maybe every two weeks.

In dry conditions, you can just monitor the robot lawn mower performance and clean the wheels when you notice performance deteriorate or when you have a spare minute in the garden.

Cleaning the wheels of a robot lawn mower is really easy and only takes 1-2 minutes. If the grass and mud is damp, I would recommend cleaning the wheels with a coarse hand held brush. This should clean the treads in a matter of seconds.

In dry conditions, the clippings can get quite impacted into the wheel treads, so I have found it better to use a flat head screwdriver or similar implement to scrape the wheel treads clean and then use a coarse brush to brush off the excess.

Either way, it only take s a few minutes, but can make a significant difference to the performance of your robot lawn mower. Even if your garden is not particularly hilly, it is a good idea to clean the underside and wheels of your robot lawn mower every 4 weeks or so.

Rain And Moisture Detection Systems

Consider purchasing a robot lawn mower that has a rain detection system to prevent the robot lawn mower from mowing your lawn in adverse weather conditions.

A number of models have rain detection systems, which will allow the robot lawn mower to prevent cutting your lawn when it is raining. Wet grass will provide significantly less traction, so if your garden has a lot of steep slopes that are at the limits of the tolerated gradient of the model, then you may achieve better performance with a model that avoids cutting your lawn in wet conditions.

Some models will not only avoid cutting your lawn in rainy conditions, but some will abort cutting activity when the rain starts. Other models have humidity sensors, and can be set to avoid cutting grass in damp conditions as well as in rain.

Thankfully, these options are configurable, so you will be able to adjust whether to activate these features. If you have experienced a very wet spell of weather, you may need to override these features to make sure the grass gets cut before getting too long.

Low Centre Of Gravity

Robot lawn mowers are designed to have a low centre of gravity. The weight of robot lawn mowers tends to be well centred in the chassis, with the battery and cutting parts low down.

This ensures that the wheels hold roughly equal amounts of the weight of the robot lawn mower, optimising traction. It also ensures that the centre of gravity is never at risk of causing it to tip over on any slopes that the mower can operate on.

Robot lawn mowers are designed like this to ensure optimal slope performance, but also with safety in mind. It would not be good to have a robot lawn mower which could tip over under operation, exposing sharp blades.

Although robot lawn mowers have lift and tilt sensors as standard, which cause the blades to stop immediately if this were to happen, it would not be desirable to have exposed blades that a curious child or pet could touch. I have written an article about the safety features of robot lawn mowers here. 

Ways To Reduce Slope Problems When Installing Your Robot Lawn Mower

There are a few measures that you can take in the setup process of your robot lawn mower to ensure that slopes do not cause any issues.

Firstly, when you are installing the guide wire of your robot lawn mower, if there is a steep slope in the middle of the lawn, you should route the guide wire across this. However, rather than laying the guide wire directly up the steep slope, you should lay it at an angle up the slope to reduce the gradient of the slope that the robot lawn mower has to negotiate while following it.

This will ensure that the robot lawn mower is always able to reach the top of the steep slope by following the guide wire and will reduce the wear on your grass.

Another thing to consider is perimeter wire placement. If your lawn slopes down steeply at the edge of your lawn, the risk of the wheels losing traction, causing the robot lawn mower to slip is increased. This is a particular risk in wet weather.

If this happens, there is a possibility of the robot lawn mower slipping across the perimeter wire, and off your lawn. If your lawn borders a flowerbed, the robot lawn mower is likely to get stuck. This can also lead to the robot lawn mower detecting that it is outside the perimeter wire, which will cause it to stop working until manually replaced inside the working zone.  

A good way to reduce this risk is to install the perimeter wire slightly further from the edge of the lawn in these locations than would otherwise be recommended. The downside of this is that it may lead to a strip of grass next to the edge of the lawn not being cut.

However, this is quite a normal situation with robot lawn mowers generally. You are highly likely to have to do some maintenance of the edge of your lawn regardless of what model of robot lawn mower you choose, so I don’t think it makes a major difference if there is a few extra centimetres at the edge that needs trimmed manually.

Consider A Planted Area Or Retaining Wall For Very Steep Slopes

Some people have lawns that are generally flat, but have sections that are very steep. Some people manage hilly gardens by having terracing work done, to have flat sections and very short, steep slopes between them. Often, these steep terraced sections are finished with grass which makes them extremely challenging to cut, either by a manual or robot lawn mower. It may be better to look for an alternative option for these sections.

One option would be to convert the slopes into planted areas, with plants that will require low maintenance. Another option would be to convert the steep slopes between flat sections into retaining walls. This will get rid of the need to mow a very steep section of grass and will actually increase the area of flat lawn in your garden.

My sister has just moved into a new house where the back garden falls away steeply at the back. The lawn is flat as you look out on the back garden, but then becomes very steep at the bottom. Prior to having her lawn laid, she made the decision to have the steep section terraced, increasing the area of flat lawn adjacent to the house.

Beyond the retaining wall, the ground drops approximately 5 feet onto a small flat section at the bottom of the garden, which has now been planted as a flower bed. This results in her having a fairly large, flat, rectangular shaped lawn. It’s significantly improved the usability of her garden and means that her lawn would be perfect for a robot lawn mower.

Obviously, this option is going to be easier and less costly if it is done when landscaping your garden or before moving into a newly built home, but could be a good project for anyone wanting to improve their garden.

What Slopes Can Robot Lawn Mowers Manage

I have provided a simple list of the maximum slope tolerance of a wide range of the most common robot lawn mowers available on the market today. There is considerable variation between models that are designed for small gardens, whilst models that are suitable for the largest gardens can all generally manage slopes of 19° to 25°.

If your garden has no gradient greater than 8.5°, then you can be safe knowing that all robot lawn mowers on the market are able to tolerate slopes at least as steep as this. Only the entry level models from Robomow have this, lesser slope performance, with all other models able to handle at least 14°, which is surprisingly steep.


Robomow RX12U

Robomow RX20U 

14 °

Flymo 1200R

Husqvarna 105

McCulloch ROB 1000

Gardena Sileno City 250

Gardena Sileno City 500

Gardena R70LI


Bosch Indego 350

Bosch Indego 400 Connect     


Gardena Sileno

John Deere Tango E5   


Worx Landroid S WR105SI

Worx Landroid M WG790E.1

Worx Landroid L WG797E.1

Worx Landroid L WG798E

Husqvarna 310

Husqvarna 315

Robomow RC 304 Pro

Robomow RC 308u

Robomow RC 312 Pro SX

Robomow RS Royal RS615 Pro X

Robomow RS Royal 625 Pro

Robomow RS Royal 635 Pro SX     


Ambrogio L60 Deluxe        


Ambrogio L85 Evolution

Husqvarna Automower 420

Husqvarna Automower 430X

Husqvarna Automower 450X

Ambrogio L85 Elite

Ambrogio L250i Elite S Plus


Honda Miimo 3000


Having considered the slope and hill performance of robot lawn mowers, there are some other things you should think about when reading further and considering getting a robot lawn mower for your garden. I have written a really useful guide outlining the things you need to consider before purchasing a robot lawn mower. 

There are also loads of other articles on this site, detailing all aspects of robot lawn mowers, which I hope you will find useful. I have thoroughly enjoyed learning about and using robot lawn mowers over the last few years and have tried to pass on my experiences on this website.