Electric Lawn Mower Study Results

Spring is right around the corner! And as it brings rainy weather, sunny days, and blossoming landscapes, it will also bring back a temporarily forgotten noise on campus: lawnmowers. While pretty much every student (and most professors) on campus has sat through class and gritted their teeth in frustration as they were unable to hear their peers over the roaring of a diesel mower engine, the loud and disruptive noises are far from the worst problems diesel-powered lawnmowers pose to the Williams community.Image of a green electric lawn mower parked on short grass

Much more pressing are the machines’ extensive environmental and human health impacts. Landscaping makes up about 5% of air pollution in the US annually. A 2015 study by the EPA found that in 2011, gasoline-powered lawn and garden equipment emitted approximately 26.7 million tons of air pollutants and accounted for 24%−45% of all nonroad gasoline emissions in the US. Another study estimated that cutting grass for one hour is equivalent to driving a car 100 miles. Among the pollutants are volatile organic compounds, carbon monoxide, nitrogen oxides, and particulate matter. These toxins have been linked to numerous health issues, including cardiovascular disease, cerebrovascular disease, kidney disease, diabetes, and numerous pulmonary diseases. Furthermore, the college’s diesel-powered mowers generate noise levels between 80-90 dB, which can cause hearing loss after two hours of exposure. These loud noises and toxic particulates pose the greatest health risks to Buildings & Grounds’ landscaping team, who come in much more frequent and close contact with the mowers.

So, what can be done about diesel-powered lawnmowers and their numerous environmental and human impacts? This fall, I conducted a cost-benefit analysis of electric lawnmowers on Williams College campus, analyzing three mowers that the groundskeeping team owns: the diesel-powered Toro Groundsmaster 3280, the Toro Groundsmaster 4100, and the electric Mean Green Rival. In addition to analyzing the environmental and human costs and benefits of switching to electric mowers, I also analyzed the economic impacts, as many people hesitate to make the switch because of the preconceived notion that electric vehicles always cost more than gas and diesel-powered vehicles. My research, calculations, and analyses yielded both expected and surprising conclusions.

Economics:  Counter to the commonly-held belief that electric vehicles are more expensive than gas-powered ones, electric lawnmowers would generate substantial savings for Williams. The electric Rival (purchase price $33,669) is slightly cheaper than the Groundsmaster 3280 of a similar size ($45,000), and less than half as expensive as the Groundsmaster 4100 ($86,000). The Rival becomes even more cost-effective when looking at the Operations & Maintenance costs, as electricity is much cheaper than diesel and electric machines have reduced maintenance costs. On a 10-year lifetime scale, we estimate that the Rival is 3.5 to 5 times cheaper than the Toros.

Annual and Lifetime Costs based on a Per Time and Per Acre Calculation

Machine On a per unit time basis On a per acre basis 
Annual Cost Lifetime Cost Annual Cost Lifetime Cost
Mean Green Rival $1,390.77 $47,576.71 $806 $41,729
Toro Groundsmaster 3280 $12,438.72 $169,387.20 $9,732 $142,420
Toro Groundsmaster 4100 $14,335.26 $229,351.60 $8,754 $173,540

Environment: As expected, electric lawnmowers are significantly better for the environment than their gasoline-powered counterparts, at least in terms of CO2 emissions. Even though electric mowers do not produce carbon dioxide emissions during use, the electricity that powers them may be generated from non-renewable sources. The New England power grid is relatively clean and minimizes the Rival’s CO2 emission. I found that over the course of 10 years, the Rival releases approximately 474,500-693,300 fewer lbs of CO2 than the Toro mowers.

It is important to note that carbon dioxide emissions are not the only environmental concerns surrounding lawnmowers and that electric mowers are not a flawless environmental solution. The Rival, like many other electric machines, uses a lithium-ion battery. Mining lithium is an environmentally damaging process that requires incredibly large amounts of freshwater (approximately 2.2 million liters to produce one ton of lithium) and releases numerous toxins into the air and water. The extraction and degradation of water resources can have disastrous socioeconomic implications on nearby communities. The Rival remains environmentally preferable due to its significantly lower  CO2  emissions, but it is not a perfect solution, and we should aim to also reduce mower use as much as possible.

Human Impact: Electric mowers, due to their lack of tailpipe emissions and reduced noise levels, have positive health impacts on members of the Williams community, especially their operators. The lawnmower’s other impact on people at Williams  relates to groundskeepers’ ability to do their jobs. The groundskeeping team I interviewed had mostly positive reviews of the Rival mower but also emphasized its current limitations. It does not release fumes, it is quieter (78 dB while mowing and nearly inaudible while in transit), it makes a better cut on flat lawn, it is easier to control its cutting height, it requires much less maintenance, and it is easier to charge. However, due to the new technology, the Rival falls short in some critical areas: it is slower (due to both its size and engine power), it does not handle steep or wet terrain very well, and it does not have any multi-use purposes, such as leaf blowing, seeding, or snow plowing. They expressed a strong desire to not replace their entire fleet of mowers with electric machines right now. Because groundskeepers are the people who will be most impacted by electrifying Williams’ fleet of lawnmowers, they should be actively engaged in the decision-making process, and their opinions on the matter should be taken into the highest regard.

Man sits smiling on a green riding mower
Groundskeeper Jaye Boucher shows off the new electric lawn mower.

In conclusion, I found that electrifying its lawnmowers would save the school money, mitigate the college’s climate and environmental impacts, and benefit the grounds team and campus community at large. Based on these findings, we recommend that Williams develop a plan to replace most of its diesel-powered lawnmowers with electric lawnmowers over the course of the next ~10 years, and should include Tim Roberts and the grounds team while developing a transition plan. Williams should also consider buying the larger Mean Green mower, the Evo (which has a 72” cut in comparison to the Rival’s 60” cut, and is faster and more powerful).

However, it is currently infeasible to replace all the school’s diesel mowers with electric mowers, as doing so would make grounds team members’ work much more difficult and nearly impossible in several locations on campus, namely hills and large expanses of tall grass, especially under rainy conditions. However, if Williams reevaluates its landscaping practices more holistically (which could be an exciting project for the Zilkha Center to undertake in the future!) and allows these difficult-to-mow areas on Williams campus to grow into pollinator gardens or fields that do not require regular mowing, a complete switch may be possible in the future.

Annika Harrington ’23 is an intern with the Zilkha Center for Environmental Initiatives at Williams College.