We are testing electric lawn mowers by running each one through a battery of tests (no pun intended, because we do actual battery tests) and yes, we also mow things. There are certain product categories where we collect, at that time, a significant amount of data, but despite our best efforts, data alone cannot give us the full picture of which product performs best. Taking it out into the yard is the best way to help filter and decode the data we have.
Battery tests
Let’s start with those battery tests. This isn’t too complicated, but actually setting it up can be a bit difficult. To measure the voltage and amps that the mower draws while running, we have to insert our meters between the battery and the mower. The physical process varies a little from mower to mower, but once set up, we get a measurement of the DC voltage and amps moving between the battery and the mower, giving us an idea of the mower’s motor power (in watts).
We take these measurements at zero load, which means we are not cutting the grass at that time or providing any resistance against the blades, which would change the numbers, making them higher to account for the higher limits of engine power. Our next round of testing updates will include upper power limits as well.
RPM tests
Yes, we definitely measure blade RPM on electric mowers. CNET’s eagle-eyed lab crew has developed the ability to calculate dozens of revolutions per second in an ultra-precise manner. Just kidding, though, we have a measuring device for that. We actually take a little bit of reflective tape and put it on the mower blade, then point the measuring tool so that the laser light overlaps that tape and we get an accurate reading of the blade’s rpm.
You can see our test scale in blue in the center below the safety glass.
Now, if we combine these numbers with other numbers like blade lengths and weights and add some kinetic force calculations, we can estimate things like the amount of force, in newtons, that the blade exerts on the grass. These numbers are not very useful. Most people would have no idea what 5 Newtons of force compares to. We prefer to go the route of comparing power outputs to something people are more familiar with; In this case, horsepower.
Gas-powered push mowers vary in horsepower, but most land in the 3 to 5 horsepower range. Upper limit numbers will be added in our next update, but you can see that the lower end in horsepower for the electric mowers we tested ranged from about 0.1 to 0.6 horsepower. This is not much. In general, you should expect to see electric mowers triple that number toward their upper limits, so we’re looking at a ballpark of 1.75 horsepower. You’ll be hard-pressed to find gas-powered retail mowers that make less than 2 horsepower.
Noise level
We talk a lot about volume, especially with external instruments. Historically, these gas-powered outdoor tools were very expensive. (Try to sleep in when all your neighbors are mowing the lawn early on the weekends.) With the advent of electric power tool platforms, all of this has changed. Your neighbor could be obsessed with taking care of the garden while you nap all day.
We tested the decibel level of mowers from the perspective of the person operating them. We install the decibel meter fixedly and take the measurement. The results weren’t too surprising, as our quietest mower was the smallest, the 13-inch Litheli, with a frequency of 68.6 dB, and the loudest was also the most powerful mower, the Ego, with a frequency of 86.7 dB.
Speed tests
You might normally think of mowers moving at a certain rate, specifically, at whatever rate you push them. An increasing number of mowers now come with self-propelled options. Many of these electric-powered mowers allow you to use this function even when the blades are not running.
We measure how fast mowers move in miles per hour. You won’t visit any rapids with these, but if you plan to use this mode, it may help you decide which ones to catch or pass. The Ryobi had the widest range of speeds to choose from but fell slightly short of being the fastest mower. The Ryobi topped out at 3.03 mph and the Greenworks Pro at 3.33 mph.
Some mowers, like this Kobalt model, can break down due to grass clippings.
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