Greenworks 20-Inch 40V Twin Force G-MAX Review USA – Cordless Lawn Mower

The Greenworks 20-Inch 40V Twin Force Cordless Battery lawn mower is one of the best selling cordless lawn mowers in the US, but is it all what it’s cracked up to be?

The Greenworks 25302 is indeed packed with features you would expect to see in higher end cordless mowers and certainly has the ability to cut a lawn in excess of 1000 meter square (roughly the size of 4 tennis courts) , but it needs to be compared to it’s nearest rival, the BLACK+DECKER CM2040 40V Lithium, to judge how good this mower really is.

To compare Greenworks 25302 to other cordless mowers in higher or lower price range would distort the results, these two mowers are probably the most affordable and best performing 40v cordless mowers on the market today.

Below I’ll be detailing all the features and functions of the Greenworks 20-Inch 40V Twin, both good and not so good and then comparing to the BLACK & DECKER CM2040 40V so you understand exactly what you’re getting for your money.

Main Features:

    • Rating: 9/10
    • Covers areas exceeding 10,800 square feet (½ acre or less) (1000m²) in size
    • 2 batteries –  1 x 40V, 2Ah and 1 x 4.0Ah Li-on battery (UK version supplied with 2 x 40V, 2Ah)
    • Blade length: 20 inch (50 cm)
    • Number of Cutting Height: 5 – 1.15 inches to 3.5 inches (35mm-85mm)
    • Grass box capacity: 13 Gallon (60 L)
    • Charge time: 60 + 120 minutes
    • Free run time: 70 minutes

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Power System

Like many cordless lawn mowers, the Greenworks 20-Inch 40V Twin is powered by two Lithium-ion battery (40V) and electrical motor which it will charge in around 3 hours. The battery is removed from the mower for charging and storage.Greenworks Dual Battery

There is a downside however.

Each battery needs to be charged individually as the charger can only charge one battery at a time, it could take up to 3 hours to fully recharge, however, this will produce a very respectable mowing time of around 70 minutes.

In comparison the BLACK+DECKER CM2040 40V that takes 60 minutes for each battery to charge (total 120 min) but gives a shorter mowing time of around 40 minutes for both batteries. This naturally depends on the condition and length of the lawn.

Unlike the Greenworks only one battery can be made active on the mower, with the Black & Decker providing a storage compartment for the second battery, with the Greenworks once one battery is drained the machine automatically switches over to the second battery.

With both mowers, only one battery can be charged at any time. I also found that the charger with the Black & Decker will not allow the battery to be recharged immediately after being used and needs a considerable period of time (40min) to allow the battery to cool down, so bare this in mind when comparing charging times.

So in summary, the Greenworks 20-Inch 40V will give much longer mowing time than the Black & Decker CM2040 with very little difference in relation to charge time (comparison table below).

Greenworks Corldess Mower

But in saying that the mowing/charging time doesn’t directly affect you if it’s enough to cut the entire lawn with no rush to charge the batteries for the next cut.

Also, the power system is completely electric so it produces zero emissions and works extremely quietly. Which is quieter? well there’s not much between them but would say the Greenworks 20-Inch 40V is slightly quieter than the CM2040, but really there is nothing in it that you would notice .

The great thing about these mowers is that you can set out to work at any time you want without it annoying you, your family or your neighbours, and with zero emissions look after the environment as well.


Model Comparison
MowersGreenworks 20-Inch 40VBLACK+DECKER CM2040
Lawn Coverage10,800 square feet (1000m²)10,800 square feet (1000m²)
Noise Level96 dB101 dB
Mowing Time70 minutes40 minutes
Charging Time60 + 120 minutes = 18060 + 60 minutes = 120
Cutting Width20 inch (50 cm)  DualBlade20 inch (50 cm) EDGEMAX
Weight42.5 lbs (19.2kgs)55lbs (25kgs)
Grass Box Capacity13 Gallon (49 L)15 gallons (56 L)
Cutting Heights5 steps –  1.15 inches to 3.5 inches (35mm-85mm)6 steps –  1.5 inches to 4 inches (38mm-100mm)


The The Twin Force G-MAX Lithium-Ion Mower has a 20 inch cutting width with two blades that do not overlap but come very close to each other. The dual metal mower blades gives it very effective benefits…GreenWorks 25302 dual blades

  1. Having two blades provides for a very fine mulch cut. Blades of grass are cut smaller and finer making it more easily absorbed into the lawn.
  2. The two blades allow for a wide 20 inch cutting width right to the edge of the mower.
  3. Metal blade generally wear less quickly than plastic blades which results in you needing to replace the lawnmower blades more often than a lawnmower that uses a metal blade.
  4. Metal blades are generally sharper and provide a cleaner cut to the grass blade, resulting in a neater, tidier and superior finish to your lawn and garden. The metal blades on the Twin Force G-MAX can be sharpened when needed unlike plastic blades.

This again does put it ahead of competitors and it’s good that Greenworks have taken advantage of what is clearly the most effective cutting system in the market.

So in summary, this mower cuts extremely well whether or not you are collecting the clippings or mulching.

It can’t all be good?

Well, no. There are a couple of small disadvantages of having the two blades and to some extent puts this mower a slight disadvantage to the Black and Decker CM2040.

  1. The two blades turn in different directions so you do not have the option for side discharge as you do with the CM2040. You only have 2 options, mulching and rear bagging because of the dual blade design, it does not offer side discharge feature.
  2. As the blades do not overlap (but come very close) you sometimes can see it miss the odd blade of grass. This is very picky and will not even be noticed by the majority, but worth a mention.

Height Adjustment

In order to combat the changing season and to continually improve the look of your lawn, you can adjust the height at which the Greenworks 20-Inch 40V Twin Force Cordless Lawn Mower (25302) cuts at. This is done very easily using the large single lever located on top/side of the mower.

Set of 2 GreenWorks 29712 10 inch Mower Blades G-Max Twin Force 25302

It lets you choose to cut from anywhere between 1.15 inches to 3.5 inches (35mm-85mm) with 5 separate cutting lengths. Just make sure you don’t set it at the shortest setting from the when the lawn has significant growth, instead start at a much higher setting and gradually work your way down. This gives the areas of small grass to catch up with the long, resulting in a more even garden.

As well as being able to sharpen the blades, it is also possible to purchase a replacement blade. Replacing the blade is relatively easy for anyone with basic DIY skills and tools.

Cutting Diameter and Height

The cutting diameter of the mower is a very respectable 20 inch (50 cm) and is perfect for those with lager lawns and no narrow strips to navigate, reducing mowing time and giving you more time to put you feet up to admire you beautiful lawn.  Now, compared to it’s counterparts with smaller widths, this might be a potential disadvantage; however, it could also be beneficial if it’s to be used in a smaller areas and lawns with narrow strips.

You may well be thinking that for a mower with such a large cutting width you would have to compromise on having a heavy and difficult to manoeuvre mower, well that’s not the case with the Greenworks Twin Force G-MAX. At just 42.5 lbs (19.2kgs) it is one of the lightest mowers in this class and size range and weighs up to 30-40 lbs lighter than a gas/petrol mower – WOW!.

When you need a mower that’s light in weight and going to get your lawn mowed in the shortest time possible, this may well be the best option, the Greenworks Twin Force G-MAX could be the cordless mower of choice.

Grass box capacity

As with all larger cordless lawn mowers the grass box is going to hold much more than it’s smaller counterparts, however 13 Gallon (49 L) is a little smaller than the Black and Decker CM2040 at 15 gallons (56 L). 13 Gallons will still allow for longer periods of use without needing to empty grass clipping as often.

The grass box on the Greenworks Twin Force G-MAX is very easy to remove and the grass clipping empty from the box with no obstructions.

An airflow tab located on the bag tells you when the bag is full, eliminating any guesswork about when it needs emptying.


The light weight, oversized 10-inch wheels and the large cutting width make this mower excellent for larger lawns or lawns with slopes or are uneven.

This really will make lawn care much easier and really makes the entire experience much less dependent on you struggling with a heavy over sized gas mower.

As with all cordless lawn mowers, not being tethered by the cord not only makes it easier to mow the lawn, but safer, quieter and more environmentally friendly.

Does this make it more practical the it’s closest competition? well, yes I think it does for people with large lawns that have a need for longer running/mowing time. There is also a fold away handle that makes carrying and storing the mower in the garage or shed very easy.

Safety Features

What I really like about the Greenworks Twin Force G-MAX is the addition of a removable safety key that disables the lawnmower to help prevent accidental starting. This is a nice feature not found on similar cordless mowers that give peace of mind around children.



As with almost all Greenworks electric corded and cordless versions are capable of mulching. The Greenworks Twin Force G-MAX seems to do this very well due to it dual blades that produce a fine and very small mulch.

What’s Included in the box?

  • The mower itself
  • (1) 4AH Battery, (1) 2AH Battery, and Charger (40V)
  • 13 Gallon (49 L) Grass Box
  • Mulch Plug
  • 4-years warranty (2 years for the batteries)


  1. This mower is not self propelled – but it is really light enough that it doesn’t matter so much.
  2. You can only charge one battery at a time, so a second charger may be required if this is an issue for you.
  3. This mower can struggles in a really dense grass areas. Be prepared to make more passes in such a condition, however, this is a problem most cordless mowers experience.

Now the above may sound trivial and are common to most cordless mowers but should be taken into consideration anyway. They are part of the package and it’s better being aware of them before a purchase than after.

GreenWorks_G-Max Twin_Force 25302Conclusion

Overall this is a very good mower, I actually rate it higher than the Black and Decker CM2040 Lawnmower due to it’s light weight, portability and good build quality. It also feels more powerful, this is probably due to the built in auto throttle, which automatically adjust power to the cutting blades so the mower is not working harder than it has to.

The extra features like the removable safety key is a nice touch but one that you most probably never use, besides you want features that will help achieve a lovely looking lawn with least amount of work and effort.

The  Greenworks Twin Force G-MAX is very proficient at cutting varying lengths and thickness for such a lightweight cordless mower. It’s worth mentioning that by cutting more regularly and avoiding very long or wet grass this should avoid not putting too much strain on the battery. Remember to always keep the battery charged and in a dry place over winter.

With this mower you’re getting features normally found in high priced gas/petrol mowers, so this is a very reasonable price at under $300 (£325 in the UK).

But do I think it’s better than its closest competitors?

Yes I do!

At this price range this really gives great value for money and you would be very hard pressed to find a cordless mower that performs this well, and has such a good build quality for this price. To get the best out of this mower you will need to cut your lawn more regularly and not let the grass grow too high or dense as it may struggle to cut very dense grass, this is however common with all cordless mowers at this price point and specification.

Overall I think this is a fantastic mower and I encourage everyone with a larger garden to purchase one. In fact I think it’s the best mower at this level you can get right now!

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Should You Buy This Model?Greenworks G MAX 40V

Well there are a few factors to consider first, whether or not you purchase this model really depends on your garden and situation.

To give you some guidance on which type of customer would suit this model best, below I’ve got a list of the categories they would fall under:

  • Their garden is less than 10,800 square feet (½ acre or less) (1000m²) in size
  • Like the convenience of having no power cord or have limited or no access to a power source in the garden but still get up to 70 minutes uninterrupted mowing time
  • Those who want to mulch and cut grass with the same mower
  • Need a wide cutting deck (20 inch (50 cm) ) to get the lawn cut with fewer passes
  • They don’t have narrow strips of grass less than 20 inch (50 cm)
  • Storage is not limited as this is a larger mower

Of course this is open to interpretation so if you don’t fall under every single one then don’t worry I’m sure you’ll still love this product. It has loads of great features that I’m sure you make use of even if you’re not its perfect customer.

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Frequently asked questions (FAQ)

Below are some questions I get asked about this mower and cordless mowers in general. Please feel free to contact me at if you have any further questions or need some advice.

Is this mower self propelled?

No – Its lightweight so not necessary.

What is the warranty period for the G-Max?

The mower has a four year warranty and the batteries are covered for two years.

What batteries come with this mower?

It comes with one 2AH and one 4AH USA Version  (2x 2AH with the UK Version)

Does the Twin Force give a nice even cut or do you have to mow the same area over again?

It gives a very good cut and is great at mulching.

What’s the run time on a fully charged battery?

Depends on how tall and thick your grass is. An average mow will give you a maximum of 70 minutes battery life.

How long does the battery take to charge?

The 2AH battery takes an hour and the 4AH two hours.

Does the mower come fully assembled?

Amazon send it almost assembled. You’ve just got to assemble the handle and charge the battery.

What size bladed does the mower take?

Two 10 inch blades.

Is the G-Max handle adjustable?

No, not adjustable but it does fold for storage.

Do you have to remove the batteries to charge them?

Yes you do.

Does the Twin Force come with a charger?

Yes the charger is supplied.

Where should I purchase this model?

Amazon have the best prices that are difficult to match and probably the most reliable delivery system on the web. Considering how valuable this piece of equipment is you want the most for your money and the best service possible making Amazon the best place to go.

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Additional Specifications
Working Area10,800 square feet (1000m²)
Cutting width20 inch (50 cm)
Cutting height steps5
Cutting height max3.5 inches (85mm)
Cutting height min1.15 inches (35mm)
Cutting height adjustmentCentral
Collector volume13 Gallon (49 L)
Battery Type2 batteries –  1 x 40V, 2Ah and 1 x 4.0Ah Li-on battery
Typical Charging Time60 + 120 minutes
Typical Mowing Time70 minutes
Vision WindowNo
Right or left start switchLeft and Right
Foldable handlesYes
Battery power indicatorYes
Grass bag filling indicatorYes
Front Wheels7 inches (17.78cm)
Rear Wheels10 inches (25.4cm)
Product Size HxWxD21 x 22 x 32 inches
Weight42.5 lbs (19.2kgs)
Lawnmower Product Expert, Reviewer and Author at | 01284 615144 | | Website | + posts

As a seasoned expert in the field of garden power tools, I have dedicated over a decade to working with and reviewing a wide variety of lawn mowers. My extensive experience has allowed me to gain a deep understanding of the benefits and limitations of different types of mowers and garden tools.

Over the years, I have honed my skills in writing informative articles and creating helpful videos for various blogs and publications. This has given me the ability to not only recognise what makes a good lawn mower, but also to help you choose the perfect garden tool for your specific needs and requirements.

With my wealth of knowledge and expertise, I am confident that I can provide you with valuable insights and recommendations when it comes to selecting the right lawn mower for your lawn. So, whether you're looking for a battery cordless, electric, petrol, or robotic mower, you can trust in my expertise to guide you towards the best option for your garden. Protection Status

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