As a test to see what I’ve learned at college, I was handed a recent lawn equipment catalog and asked to point out the falsities of a particular ad–a typical breakfast in the Pitel household.  The ad in question was for a fully electric lawn mower.  The mower was featured in a nice two page spread, but my eyes immediately shot to the specs.

Right off the bat, you can tell the numbers for “Run Time” is off.  A 24 V, 10 Amp hour battery will not run a 24 V, 21 Amp motor for 60 minutes.  Ideally, it will provide (24 V * 10 Ah)/(24 V * 21 A) = 0.48 hrs = 28.5 minutes.  By draining the batteries faster than the rating (10 Ah battery at 21 A), you limit the run time even more.  Best case scenario, you’ll probably get 25 minutes on a charge, which is barely enough time to cut a small lawn.  But hey, maybe you’re not running the mower at full load (i.e. just driving it around for fun) and since they worded it very carefully to say “up to 60 minutes,” we can give them the benefit of the doubt.

The second falacy is a quote splattered in big print across the center of the ad: “It cuts my lawn as well as any gas mower…”  The following is taken from their website:

Taking a look through the rest of the catalog, I came across their lowest powered gas lawn mower.  The gas lawn mower was rated at 5.5 HP–that is, 5.5 horsepower.  Okay.  The maximum power rating for the electric lawn mower was (24 V * 21 A) = 504 Watts.  The tricky part for me during this little test was remembering the conversion from Watts to horsepower (I said 740 when it’s actually about 746 watts per horsepower).  So (504 Watts / 746) =  0.67 HP!  Now how can a company advertise that this electric mower gives a comparable mow to a gasoline mower, when it provides less than 15% the power. To account for the lower power, they have reduced the cutting width to 14″ when a typical small lawn mower is 20″ or more.  This decreased width means it’ll take a lot longer to cut your lawn.  In addition, many users have reported that it cannot cut tall grass (again, due to the limitations of the motor). 

In summary, if you want a light and small lawn mower and are concerned about fumes, then you should consider an electric mower.  Otherwise, a gas mower would be more economical.

I passed the test with an A-, losing points for being 6 off on the horsepower conversion (tough grader).