We test electric mowers by going through a battery of tests (no pun intended, because we do real battery tests) and yes, we mow stuff too. There are certain product categories where we collect, at the time, tons of data, but despite our best efforts, data alone cannot give us the full picture of which product is performing best. Taking these to the backyard is the best way to help filter and decipher the data we have.
Battery tests
Let's start with those battery tests. This one isn't too complicated, but it can be a bit tricky to physically set up. To measure the voltage and amps drawn by the mower during operation, we have to insert our measuring devices between the battery and the mower. The physical process varies slightly from mower to mower, but once it's set up, we get a measure of the DC voltage and amps running between the battery and the mower, which gives us an idea of the mower's motor power (in watts).
We take these measurements at zero load, meaning we are not cutting grass at the time or otherwise providing resistance against the blades, which would change the numbers, making them higher to account for the higher engine power limits. Our next round of testing updates will also include those upper power limits.
RPM tests
Yes, we absolutely measure blade rpm on electric mowers. The eagle-eyed lab staff at CNET have developed the ability to count tens of revolutions per second in a super-precise way. Just kidding, we have a meter for that though. In reality, we take some reflective tape and place it on the mower blade, then point the measuring tool so that the laser light overlaps that tape and get an accurate reading of the RPM of the blade.
You can see our test meter in blue in the center under the safety glass.
Now, if we combine those numbers with others, such as the lengths and weights of the blades, and put in some of our engine power calculations, we can estimate things like the amount of force, in Newtons, the blade exerts on the grass. Those numbers aren't too helpful. Most people won't have much of an idea what 5 Newtons of force is comparable to. We prefer to go the route of comparing power output to something people are more familiar with; in this case, horsepower.
Gas powered push mowers vary in horsepower, but most of them land in the 3 to 5 hp range. We'll add the upper limit numbers for our next update, but you can see that the lower horsepower limit for the electric mowers we tested ranged from about 0.1 to 0.6 hp. That is, not much. In general, you should expect to see electric mowers triple that number toward their upper limits, so we're looking in the 1.75 hp space. You'd be hard-pressed to find retail gas-powered lawn mowers that run under 2 hp.
Noise level
We often talk about sound level, especially with outdoor type tools. Historically, these outdoor gas tools have been quite loud. (Try sleeping when all your neighbors are mowing early on the weekends.) With the advent of power tool platforms, all that changes. Your neighbor may be obsessing over lawn care while you're putting the day away.
We tested the decibel level of the mowers from the point of view of a person operating it. We install a stationary decibel meter and make the measurement. The results weren't too surprising, as our quietest mower was the smallest, the 13-inch Litheli at 68.6dB, and the loudest was the most powerful mower, the Ego, at 86.7dB.
Speed tests
You might think that lawnmowers move at a certain speed, or rather, whatever speed you push it. A growing number of mowers now come with self-propelled options. Many of these electric mowers allow you to use that feature even when the blades are not working.
We measure how fast mowers go in miles per hour. You won't be visiting any ramps with these, but if you plan on using this mod, this can help you decide which one to take or pass. The Ryobi had the widest range of speeds to choose from, but fell just short of being the fastest mower. The Ryobi topped it at 3.03 mph and the Greenworks Pro at 3.33 mph.
Some mowers, like this Cobalt model, can get stuck with grass clippings.