How to choose a thermal mower? What engine power?

Regular maintenance of the lawn is essential if you want to enjoy a very pleasant outdoor space, especially since a perfectly maintained land increases the value of a property. For this, of course, you need to have the right equipment. The thermal mower is essential when the grassed area is at least 600 m2. But it is available in many models, so it is not easy to choose the one that best meets your needs. Of course the most important criterion is the engine power but other characteristics are to be studied with a magnifying glass to afford the ideal thermal mower.

What is a thermal mower?

It is a gas-powered lawn mower that makes mowing the lawn easier and faster. The cutting blade is driven by a combustion engine, usually 4-stroke or more rarely 2-stroke. The engine runs on unleaded fuel and oil is essential for lubrication. Its three main versions are:

Main criteria for choosing a thermal mower

To choose the right thermal mower for your land and your needs, the selection criteria that must be taken into account are presented below.

Safety and comfort

It must be equipped with a Emergency stop buttonof a disengageable blade so as not to have to turn off the engine when the tank needs to be emptied, adjustable handlebar in height for more comfort, large wheels on ball bearings so as not to damage the lawn.

Engine power

This is THE most important selection criterion. We choose the displacement depending on the area to be mowed. The less powerful models are monocylindres while those whose power is greater than 15 hp are twin cylinders. Of course, the more powerful it is, the more fuel the thermal mower consumes.

No need to invest in a behemoth if you only have 400 m² of lawn to maintain, but a low-power motor will struggle to last long on an area of ​​1,500 m². Here is a small table giving some examples of correspondences between displacements, number of horses and kW as well as the width of cut.

Type of thermal mower




Housing width


From 130 to 170 cm3

From 3.5 to 5 HP

From 2.6 to 4.0 kW

From 40 to 50cm


From 150 to 190 cm3

From 4 to 6 HP

From 3.3 to 4.5 kW

From 40 to 55cm


From 300 to 650 cm3

From 9 to 17 HP

Minimum 6.8 kW

From 55 to 110cm

When it comes to engine choice, you might as well opt for the newest design possible. Today we have:

  • From overhead camshaft or OHC design,
  • From overhead valve or OHV design.

These two designs offer a greater performance than the old models with side valves but which can still be found.

The starting system,

Some petrol mowers are equipped with a electric starting device which operates on a rechargeable battery. It can be interesting to have such equipment but it means having to change the battery one day or another.

The mulching mower

This is a mowing technique that consists of cutting the upper part of the blades of grass into tiny pieces which are then distributed evenly over the lawn. It is thus possible in a single operation mow et divide on his land a vegetable mulch very fine which is also called the mulch. Some mowers have a mode mulching but are additionally equipped with a collection box.

This versatility is interesting since it allows the gardener to choose between recovering the mowing debris in the container or spreading it when mowing on the ground so that the crushed grass can enrich the soil with nutrients.

The self-propelled mower function, a serious asset

It is the motor that drives the mower which therefore does not have to be pushed manually since it moves forward on its own. It is guided simply and without any effort thanks to its handlebars. In the thermal version, the self-propelled runs on unleaded fuel which powers an air-cooled 4-stroke engine. It is a comfortable and powerful model, equipped with a collection box but which is also suitable if you opt for mulching.

The self-propelled version is recommended because a thermal mower is relatively heavy. We can thus largely reduce physical fatigue during a mowing session.

The casing and the covering

This is a very important point since the safety as well as the longevity of the mower partly depend on it. The housing must be able protect the user against sharp blades et hide the technical block. It must therefore be very wide.

We recommend choosing at least one dressing composite (ABS) rather than plastic if you want to have a light material. But aluminum is preferable because it minimizes vibrations, while sheet steel is more resistant but requires very regular maintenance.

The width and height of cut

The cutting width must be chosen according to the area of ​​the land. The larger it is, the fewer passages there will be to perform. For a lawn of 1000 m², we recommend a cutting width of at least 60 cm, for 1500 m² it is better to opt for a width of 90 to 110 cm while 40 to 50 cm is more than enough if the area of ​​the grassed part is less than 1000 m².

Regarding the cutting height, it is adjustable on most mowers. It is important to check this detail before buying your machine, because it allows you to make your own adjustments according to your needs and thus be able to obtain a very successful visual result.

Now that you are ready to buy your thermal mower, you finally have to do a little calculation to estimate the cost of its maintenance. This of course depends on the frequency of use since the more you mow, the more fuel and oil must be put in the mower and the more the elements of its engine wear out. Just as you do for a vehicle, you have to take care of the spark plugs, the belt, the filters and remember to replace them when necessary. For a low-power thermal mower, this cost varies between 100 and 200 €/year and is estimated at at least 300 €/year for a powerful thermal mower. As for his purchase priceit varies according to the models and the power of the engine, between 180 and more than 2,000 €.

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