Do Robotic Mowers Work on Hills and Rough Terrain?

  • By: CarlBroadbent
  • Time to read: 7 min.

Not all lawns are level and smooth and if you are used to tackling your hilly garden with a push mower or ride-on you will know that it is hard work.

A robotic lawnmower that can handle rough terrain is an ultra-convenient solution for keeping grass growth in areas with marked gradients under control.

Uneven terrain and hills can pose a challenge for even the most rugged robotic mowers, but some models are designed to mow on an incline and deliver beautifully cut lawns at a gradient.

robotic mower on hill
Robotic mower cutting grass on a steep hill

If this sounds like a great match for your garden, this brief article looks at how robotic mowers work on hills, valleys, and everything in between with features and examples of mowers that are up to the job. 

Hills and rough terrain can be a challenge for robotic mower

For a robotic mower to be effective, it needs to cut evenly on slopes and other varied terrains. Though most robotic mowers perform well on slopes and hills, they may start to slip and stop cutting the grass in areas that are too steep or uneven.

The last thing you need is the scalping of your hills…

If you have struggled for a long time with a hilly lawn, you will know that the uneven terrain wreaks havoc with larger, conventional mowers. 

One particularly frustrating problem is the scalping that happens on raised areas of the lawn when the mower passes over it.

The high spots become cut too short compared to the remainder of the lawn making them have an unsightly balded appearance that can invite the growth of weeds.

Robotic mowers are usually small enough to cope with the undulations of a rough lawn, and at a minimum can deal with slopes of 8.5 degrees.

Mowers that have large drive wheels can cope with the curvature involved and climb gradients while delivering a consistent cut.

Understanding gradients and percentage slopes

When looking for a robotic mower that can handle hilly lawns, evaluating its ability to mow on a slope or gradient is essential.

Manufacturers specify the maximum slope or working gradient for their autonomous mowers, helping you select the model that will be the most suitable for your terrain.

Here is a quick explanation of the three types of measurements for slopes you may encounter- degrees, gradient, and percentage:

  • Gradients are given as a ratio in a Y:X format. This is simply the rise in the ground level (Y) and the length of its run (X).
  • Slope percentage is also a calculation of the rise and run of the lawn. Simply divide the rise by the run and multiply by 100 to yield a percentage that you can refer to when assessing a robotic mower.
  • Slope angle in degrees is a little more complicated and requires a few maths formulas but also based on the rise and run.

To select the right mower you will need to know the slope of hills and gradients in your yard

To select the right mower, you need to know the slope of your terrain. Calculating the slope of your lawn is a fun and practical task you can do on a sunny afternoon.

All you’ll need are some canes, string, a tape measure, and high school maths. Watch this video for an easy to follow technique:

3 key features of robotic mowers that help them handle slopes

Robotic mowers that can handle gradients have certain features that help them climb and mow your hills effectively.

Notable robotic features for hills and rough terrain include:

Wheels

The wheels of mowers that handle gradients are typically large and rugged, making them able to hold the ground and get decent traction that drags the mower up the slope.

Four-wheeled robotic mowers may be more effective at this than their three-wheeled counterparts that don’t have as much drive in the front. 

Rain sensors

Wet weather creates a challenge for robotic mowers on slopes because the terrain is more slippery, making it harder to grip and cut the grass effectively.

Onboard rain sensors will cause the mower to return to its charging station when the rain begins so the mower only works when it is dry. 

Center of gravity

A low center of gravity on these mowers helps the hold to the grass on inclines rather than slipping or even flipping backward. 

Automatically adjusting blades

The mowing deck of some of these mowers is suspended and will move up and down as the mower passes over uneven ground. This makes the mower cut evenly despite the rugged terrain. 

Examples of robotic mowers that are great for hilly lawns

Though most autonomous mowers will succeed at mowing uneven ground some are more effective than others.

Here are a couple of robotic mowers that do a great job at rough sloped lawns:

Husqvarna Automower® 115H 

Technical specifications

  • Cutting width/height: 8.7 in/ 2 in to 3.6 in (5 cm/  to 9.1 cm) 
  • Maximum lawn area mowed: 700 square feet (65 square meters)
  • Maximum gradient: 30 degrees
  • Battery: Lithium-ion
  • Working time: 60 minutes
  • Weight: 20.7 pounds (9.07 kilograms)
  • Warranty: 1-year warranty
Husqvarna Automower® 115H Connect/4G Robotic Lawn Mower, Small – Medium Yards (0.4 Acres)

Description

Husqvarna is a market leader in robotic mower technology, so it is no surprise that these mowers deliver exemplary performance on varied terrain including slopes of up to 30 degrees.

These stylish robot mowers have a low center of gravity and rugged wheels with the deep tread that is needed to mow hilly areas.

The front-wheel-drive is great for getting the mower up slopes while the smaller back wheel adds maneuverability.


WORX WR165 Landroid S Robotic Lawn Mower

WORX WR165 Landroid S 1/8 Acre Robotic Lawn Mower

Technical specifications

  • Cutting width/height: 8 in/ 1.5 in to 3 in (20.32 cm/ 3.8 cm to 7.6 cm) 
  • Maximum lawn area mowed: 5445 square feet (506 square meters)
  • Maximum gradient: 20 degrees
  • Battery: Lithium-ion
  • Working time: 3.5 hours
  • Weight: 49.9 pounds (9.07 kilograms)
  • Warranty: 3-year limited warranty

Description

The WORX Landroid is a great all-rounder that has thoughtful design features that tackle problem areas in lawns like slopes and edges.

A powerful motor and large rugged wheels mean that this mower can cut on a 20-degree incline with ease.

Its efficient brushless motor provides the maximum cutting time on uneven terrain which would be a challenge for lower-spec mowers.


If a robotic lawnmower is a must for your rough terrain, you may need to tackle your lawn so the bot can mow it.

If your lawn is plagued or pitted with high and low spots that will impede your robotic mower, it may be time for some decisive action to landscape and level the lawn. 

Adding topsoil is not usually effective as a layer of 1 centimeter in thickness or more can smother existing grass.

Consider leveling the raised parts of your lawn by slicing them off with a flat spade, removing excess soil, and relaying and watering in the turf.

But for total peace of mind, you may have to re-turf the entire lawn. This is a drastic step but you can remove the turf, level the area, and lay new turf on the flattened soil.

With an even surface, you can be confident that your robotic mower does not get into trouble on its rounds.

You could also consider repurposing the steepest areas of your lawn by planting a flower bed or creating a stepped rock garden, leaving the robotic mower to tackle the more level areas.

You may also consider a ride on zero turn mower for bigger and steeper gardens. Read our guide here.

Rounding up

Robotic lawnmowers are generally effective at mowing slopes and gradients but lower-spec models may struggle with truly hilly grassed areas.

For some particularly rough lawns, leveling the lawn and re-turfing may prove to be the best solution for a lawn that a robotic mower can maintain.

By knowing the gradient of your lawn you can select a robotic mower with features that will help it cope with mowing on an incline. 

servicing a robotic mower

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