Mowers
Mower blades: mulching, high-lift, and when to change them
The cheapest upgrade on any mower is the part that touches the grass. Almost nobody thinks about it until the lawn goes brown at the tips.
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We have not tested these units. Every spec on this page comes from the manufacturer's own documentation and is linked to it. Every computed figure is arithmetic you can redo. Prices are checked daily — last verified January 1, 1970. Here is exactly how we pick.
A battery mower removes most of the maintenance a gas mower demanded: no oil, no filter, no spark plug, no carburetor. What it does not remove is the blade, and the blade is the only part of the machine that touches your lawn.
The short answer
What a dull blade actually costs you
The visible symptom arrives a day or two after mowing, not during it. A cleanly cut blade of grass seals over; a torn one dries out at the ragged edge and the whole lawn takes on a gray or brown cast at the tips. That is the jagged-edge effect described in the extension guidance, and it is also an open door for disease.
There is a second cost the extension material makes explicit and most people miss: a sharp cut helps the plant conserve water, which reduces how much irrigation the lawn needs. A blade is a watering decision as well as a cutting one.
The blade types, and what each is for
| Blade type | What it does | Best when | Trade-off |
|---|---|---|---|
| Standard / 2-in-1 | Cuts once and discharges, with a mild lift | General mowing where you are not fussy either way | Neither the finest mulch nor the fullest bag |
| Mulching | More cutting surface and a curve that keeps clippings under the deck to be recut | Returning clippings to the lawn; leaf mulching in autumn | Lower airflow, so it fills a bag less well |
| High-lift | Aggressive upward airflow to carry clippings into a bag | Bagging, and wet or heavy material you want out of the deck | More motor draw for the same swath |
| Low-lift / extended runtime | Less airflow, less resistance | Dry, light grass where you want maximum minutes per charge | Poor bagging and coarser mulch |
The last row is the one people miss. Airflow is not free: every bit of lift the blade generates is energy the motor spends. On a battery mower that shows up directly as minutes, which is why EGO includes an extended-runtime blade in its set at all.
Two ways manufacturers solve this
Swap the blade: EGO Select Cut
The LM2135SP ships with three interchangeable lower blades covering mulching, high-lift bagging and extended runtime. You physically fit the one that matches the job. It is more faff and more storage, and it is the only approach that genuinely changes the aerodynamics under the deck rather than redirecting them.
#ad Check the EGO Power+ 21" Select Cut LM2135SP price on Amazon — how we're funded.
Redirect the airflow: 4-in-1 decks
Greenworks takes the other route on both its mowers: one blade, four deck modes — mulch, bag, side discharge and, on the 80V, turbo leaf pickup. Nothing gets unbolted. The 80V publishes a 3200 RPM blade speed, which is the figure that actually determines how finely material gets processed, and neither EGO nor Toro publishes an equivalent.
#ad Check the Greenworks 80V 21" 4-in-1 LM2108S price on Amazon — how we're funded.
Blade condition and cut height are one decision
A sharp blade at the wrong height still damages the lawn. The extension guidance is specific on all three parts of it.
| Guidance | The figure | Why it matters to the blade |
|---|---|---|
| Maintain the lawn at | 3 inches or higher | Taller grass shades soil and roots deeper; it also asks more of the blade per pass |
| Mow before the grass reaches | 4.5 inches | Past that, a single cut takes more than a third and the deck loads up |
| Remove no more than | 1/3 of the leaf tissue | Exceeding this is the fastest way to make a sharp blade look dull |
| Decomposed clippings add | the equivalent of one fertilizer application per year | The payoff for keeping a mulching blade sharp |
All four from University of Minnesota Extension, mowing practices for healthy lawns, fetched 6 September 2026.
Note how the cut-height guidance interacts with what a mower publishes. The Greenworks LM2054 tops out at 3.6 inches and the EGO LM2135SP at 4 inches; a deck whose ceiling is below three inches cannot follow the extension recommendation at all. We work through that in the mowing height guide.
A blade routine that is actually short
- Take the battery out first. Every time, before the deck goes anywhere near vertical. There is no ignition to disable on a cordless mower, so removing the pack is the whole safety interlock.
- Look at the leading edge, not the whole blade. Nicks and rounding on the cutting edge are what matter; scratches on the flat are cosmetic.
- Check the lawn two days after a cut. Gray or frayed tips mean the edge has gone, whatever the blade looks like.
- Keep the profile. On a mulching blade the curve is the function. If it is bent or the profile is gone, replace rather than reshape.
- Balance after sharpening. An unbalanced blade vibrates, and vibration goes straight into the motor bearings on a machine with no engine mass to absorb it.
What we cannot tell you
We have not measured cut quality, sharpening life or the runtime difference between blade types on any of these machines. No manufacturer publishes a watt-hour figure by blade profile, so any number we gave you for what a high-lift blade costs in minutes would be invented.
What is documented is the effect of a dull blade on the plant, the cut-height window the grass wants, and the fact that two of these mowers give you a real choice of blade behavior. Use all three.
The products discussed
Specs are the manufacturer's own and linked to the page they came from. Prices come from a live daily check; where we have no verified price we say so rather than print a stale one.
EGO Power+ 21" Select Cut LM2135SP
EGO · EGO 56V ARC Lithium · Our score 9.1/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
The most watt-hours in the box of any flagship walk-behind here, on the platform with the widest tool range to grow into.
Published specs
| Deck | 21 in |
|---|---|
| Cutting torque | Up to 7.0 ft-lbs |
| Battery included | 56V 7.5Ah |
| Cut height | 1-4 in, 8 positions |
| Self-propel speed | 0.9-3.1 MPH |
| Runtime claim | Up to 60 min |
| Warranty | 5-yr tool / 3-yr battery |
Source: EGO POWER+ 21" Select Cut System (LM2135SP), egopowerplus.com
56V x 7.5Ah = 420Wh, using EGO's advertised pack voltage.
What the numbers favor
- 420Wh in the box -- the largest included pack of any flagship walk-behind on this page
- Eight cut-height positions from 1 to 4 in, the widest published range here
- Three interchangeable lower blades (mulching, high-lift bagging, extended runtime)
- 5-year tool warranty, the longest published on this page
What they don't
- EGO publishes torque (7.0 ft-lbs), not motor wattage, so it cannot be compared directly against Greenworks' 1500W figure
- The 7.5Ah pack that earns the runtime claim is also the expensive one to replace
your yard is under a quarter acre. You would be paying for 420Wh of headroom you will never discharge, and a 20 in push mower cuts the same grass.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Greenworks 80V 21" 4-in-1 LM2108S
Greenworks · Greenworks 80V · Our score 8.4/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
The only mower here that publishes motor wattage, blade RPM, weight and an acreage rating -- and the only one whose battery warranty matches its tool warranty.
Published specs
| Model / SKU | LM2108S / 2550402 |
|---|---|
| Deck | 21 in |
| Max blade speed | 3200 RPM |
| Battery included | 80V 4.0Ah |
| Cut height | 1.38-4.0 in, 7 positions |
| Runtime claim | Up to 33 min |
| Weight | 75 lb |
| Rated for | Up to 1/2 acre |
| Warranty | 4-yr tool / 4-yr battery |
Source: 80V 21" 4-in-1 Self-Propelled Lawn Mower (LM2108S), greenworkstools.com
80V x 4.0Ah = 320Wh, using Greenworks' advertised pack voltage.
What the numbers favor
- 4-year battery warranty -- a year longer than EGO's 3-year, on the component that fails first
- Publishes blade RPM, weight and acreage rating; the other two brands publish none of the three
- 40-minute recharge on the included charger, the fastest published here
- 4-in-1 deck adds turbo leaf pickup on top of mulch, bag and side discharge
What they don't
- 320Wh included, the least of the three flagships -- and the 33-minute runtime claim reflects that
- 75 lb is the only published weight here, and it is not light
you want one battery to finish a half-acre without a swap. Greenworks rates the mower for 1/2 acre but claims only 33 minutes on the included pack; those two numbers only reconcile if you buy a second battery.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Where to buy the tools on this page
Every link below is an Amazon affiliate link. We show no price we have not verified today, so where there is no live figure the link says "check price" and takes you to the listing to read it there.
Best overall
EGO Power+ 21" Select Cut LM2135SP
EGO · EGO 56V ARC Lithium
Best published spec sheet
Greenworks 80V 21" 4-in-1 LM2108S
Greenworks · Greenworks 80V
#ad As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. How we're funded.
Common questions
How do I know if my mower blade is dull?
What is the difference between a mulching blade and a high-lift blade?
Does a sharp blade save battery?
Which mowers let you change the blade type?
How high should I be cutting?
Can I sharpen a mulching blade the same way?
Sources
Read next
- Mowers
Deck width sets how fast you finish. Watt-hours set whether you finish at all.
- Battery lawn mower maintenance: what is actually left to do
Five maintenance jobs removed, one added. The short list that remains, and the storage habits that matter.
- Mulching vs bagging: which should you actually do?
The extension research on returning clippings, and what each deck mode costs you in runtime.
- Best battery mower for mulching leaves
Half an inch of leaves is the workable layer. Which decks shred it, and the cross pass that finishes the job.
- What height should you mow your lawn?
The one-third rule, the 3-inch recommendation, and every published cut-height range checked against them.
- Best battery mower for thick, tall grass
Published torque and blade speed, plus what a 20-50% heavier cutting load does to runtime.