Greenworks 80V LM2108S review

We have not mowed with this machine. We have read its specification sheet, which is the most complete one in our registry — and that completeness is what makes this an unusually easy mower to assess honestly, including where it loses.

The short answer

Everything Greenworks publishes

The cost of that transparency

That last line is worth pausing on. Greenworks' own acreage rating and its own battery size agree precisely with the 640Wh-per-acre figure we derived independently from Kobalt. Two makers, two different platforms, the same implied energy per acre — which is the strongest evidence we have that the number is real.

What the evidence says in its favor

• Complete documentation. Blade speed, weight, cut height, acreage, recharge and two separate warranty terms.
• A four-year battery warranty, the longest in our registry. Most makers warrant the pack for three years against five on the tool; Greenworks covers both for four.
• An acreage rating you can buy against, rather than a watt-hour sum you have to do yourself.
• 4.0 inch maximum cut height, which reaches the top of Clemson's published St. Augustinegrass range.
• 80V platform breadth — see the Greenworks platform guide.

What is genuinely against it

• Thirty-three minutes. It is the shortest published runtime of the four flagships, and on a half-acre lawn that rating assumes you use nearly all of it.
• Seventy-five pounds is the heaviest published weight in our mower registry — 17.5 lb more than the same brand's 40V push model.
• The highest draw of the four at 9.7Wh per minute, so a bigger pack helps it less than it would help a more efficient deck.
• A 1.38 inch floor means it cannot reach the roughly 1 inch spring height Clemson publishes for centipedegrass, bermudagrass and zoysiagrass.
• Only 320Wh in the box, the smallest single pack among the flagships.

The acreage rating, checked against its own battery

Greenworks is one of only two makers in our registry that publishes an acreage rating for a walk-behind, and it is worth testing that rating against the battery it ships with rather than taking it on trust.

So the rating is internally coherent: the battery, the runtime claim and the acreage claim all agree with each other. What the rating does not include is slope, thick growth, wet grass or a pack that has aged, all of which raise draw. Treat half an acre as the ceiling on a good day rather than a typical Saturday.

The 9.7 watt-hours per minute, examined

This is the least flattering figure on the spec sheet and it deserves a fair reading. It is the highest draw of the four flagships, but the mower is also a 21 inch self-propelled deck spinning at a published 3200 RPM and moving 75 lb, and two of the three machines it is being compared with publish neither blade speed nor weight.

That pattern is worth naming. A runtime claim with no stated conditions is easy to make generous, and the machine here that publishes most about itself also posts the least flattering efficiency number. We do not think that is a coincidence, and we cannot prove it either — which is itself the problem with the category.

What 4-in-1 actually means here

• Mulching, with the chute plugged and clippings recirculated under the deck — see best mowers for mulching.
• Bagging, which needs the airflow the deck shape generates — see best mowers for bagging.
• Side discharge, for growth too long to mulch without clumping.
• A fourth mode Greenworks counts in the name. One blade does all of them, which means one sharpening schedule rather than three.

Against EGO's three-blade approach this is the simpler system to live with and the less optimized one for any single job. Neither maker publishes a figure that would let you choose between them on results.

Who should buy it

Buy it if you want to know what you are buying — this is the mower for a reader who reads spec sheets — and if your lawn is genuinely at or under the published half acre. Buy a second pack with it if you are near that limit. Skip it if you mow a warm-season lawn that needs an inch, or if 75 lb on a slope is the problem you are trying to solve. Our EGO LM2135SP review covers the machine that answers both of those and publishes less about itself.

#ad Check the Greenworks 80V 21" 4-in-1 LM2108S price on Amazon — how we're funded.

The verdict, in one paragraph

Every figure published, an acreage rating that checks out against its own battery, the longest battery warranty in our registry, and the shortest runtime claim of the four flagships. Those are not separate observations: a maker willing to publish a real acreage rating and a real blade speed is also the maker least able to quote a flattering runtime, because the numbers have to agree with each other.

Buy it if your lawn is inside half an acre and you value knowing what you own. Add a second pack if you are near that limit, because 33 minutes is the figure the whole rating rests on.

What we cannot tell you

We have not used this mower. Greenworks publishes no conditions for the 33 minute claim — grass height, mode and self-propel use all change it — and no cold-weather derating figure, which no maker in our registry publishes for any battery. We cannot tell you how the 4-in-1 selector feels, how it folds, or whether 75 lb is noticeable on the hills the acreage rating does not mention.