The Bosch GRT18V-40N18X String Trimmer Reviewed: Finish a Large Yard in One Pass

7 min readIn my many years as a contractor, I’ve learned the secret to efficiency: Pick the right tool for the job. I’ve evaluated and recommend string trimmers that stand out due to their light weight, portability, or budget pricing. But what if you have a large property with hard-to-reach areas that can slow down the trimming process? I have found nothing beats a trimmer with a long runtime.The Bosch GRT18V-40N18X has far and away the longest battery life of any electric string trimmer I’ve tested. It’s also physically longer than most other string trimmers, allowing for greater reach beneath bushes and around obstacles.That’s not to say there isn’t a drawback to this trimmer—which there is—its hefty weight. However, if you invest in an affordable shoulder strap and pace yourself if/when the weight starts to bother you, then this string trimmer is the one you’ll want for tackling almost any job.ProsAnti-Tangle Technology prevents long weeds from clogging the trimmerLong battery lifeLong reachKey SpecsWeight12.45 lbVoltage18VBattery8 AhCutting Width15.7 in.The Bosch GRT18V string trimmer is well built, durable, and capable of tackling a wide range of tasks including light trimming and edging, plus you’ll be able to wade through hard-to-reach undergrowth.The battery delivers an ample reserve of energy, and the fast charger minimizes downtime. This is essential for lawns that are a half-acre or more in size, or for any lawn with abundant shrubs, trees, flower beds, and walkways that need to be trimmed or edged.Longer Runtime Means More EfficiencyThe longer your trimmer’s runtime, the less you’ll have to stop and swap or recharge batteries. When buying a string trimmer, take a look at the battery’s amp-hour rating (Ah) for a relative idea of runtime. The higher the Ah, the longer it will run on a single charge.While testing the Bosch, I could easily complete the maintenance of even a large yard (up to 45 minutes of actual runtime) on a single battery. In fact, if you're only using it to tidy up a small yard after mowing, it's easy to imagine that you might go a month or more on a single charge.By contrast, most other string trimmers have about 15 to 25 minutes of runtime, largely because they come with 4-Ah batteries. You may notice manufacturers typically don’t provide a runtime on their string trimmers. The reason is that runtime is heavily affected by factors such as whether you use variable speed as well as the thickness and density of the weeds you trim. The more challenging the weeds, and the higher the speed of the trimmer, the shorter the runtime.Impacting things further, many people won’t run the string trimmer continuously while trimming, but are far more likely to trim in short spurts. In other words, your runtime will depend on what you’re trimming and how you trim it. So not only for safety reasons but also for battery life, it’s best to keep your finger off the trigger anytime you’re not actively trimming.Dan StoutThis Bosch trimmer, 75 inches in total length, has 8 to 30 inches of additional reach compared to other trimmers I have tested. That means better access beneath bushes and around obstacles.A Sensitive Trigger Gives You More ControlThe GRT18V excels with a number of features that make it stand out for day-to-day use.I found the variable-speed trigger smooth and intuitive—the more you press the trigger, the faster the head turns. I’ve used trimmers where the trigger is jerky or unresponsive, making the variable-speed barely usable. By contrast, the Bosch’s sensitive trigger allowed me to find exactly the right balance of speed and control. I was easily able to slow down to control debris spray or speed up when I tackled thicker weeds.The GRT18V also boasts anti-tangling technology. This stops the head’s rotation if it senses a potential jam that is caused by tall or thick weeds. I noticed it in action when I purposefully ran the tool into metal lawn furniture; the trimmer didn't snag and pull tight, the way many powerful string trimmers can. This safety feature can prevent the tool from getting snapped forward and possibly doing more damage than it would on its own.Replacement string is fed through the head and wound around the spool by cranking the head. The line feed is clearly labeled, and there’s no need to open the head to reload string, as with some older or budget trimmers. The result is that you can quickly reload your string with minimal hassle. It uses 0.08- to 0.095-inch string, which is thick enough to slice through even heavy yard growth. As the string wears down, you’ll need to let more out with what’s known as a “bump feed”—tapping the trimmer head against the ground as it runs.The trimmer functioned well as an edger. I was able to easily maintain clean, straight lines, and it had no problem cutting through overgrowth along sidewalks and driveways. I typically flip trimmers on their side to edge, and you can certainly use the GRT18V in that fashion. If you prefer to hold the trimmer vertically while edging, the GRT18V has a secondary trigger lock on the grip, which makes vertical edging easier.With an overall length of 75 inches, the Bosch GRT18V had anywhere from 8 to 30 inches of additional reach compared to other trimmers I tested. That additional size allowed me to reach between trees and under bushes to trim without having to brush against branches and brambles.Battery Knowledge Is (Battery) PowerIf you want proof that the usefulness of a modern power tool is determined by the battery as much as the tool, all you need to do is look at the price of the individual parts. When sold as a tool with no battery, the trimmer sells for $230, while the battery and charger alone sell for $250.The charger included with the GRT18V has a trio of charging options. Standard is its default charging method, while Power Boost rapidly charges to 50 percent capacity, perfect for getting back to work quickly. Long Life mode charges the battery to 80 percent, at a slower rate in order to prolong service life.Even in Standard mode, during my testing, it took an 8 Ah battery from complete discharge to fully charged in less than 45 minutes. Most other trimmers I’ve tested take between two to four hours to charge, depending on the charger and amp-hours. I really only ever needed Standard or Long Life mode, but if you think you might need more than a single charge, Power Boost will save a ton of time and get you back to work fast.The GRT18V string trimmer is compatible with all of Bosch’s 18V batteries, as well as select batteries from other AmpShare partners (such as Fein and Wagner). So although the battery adds significant expense for the complete string trimmer package, you can use it in other tools, adding to its utility.You May Need a Shoulder StrapThe downside to this trimmer is its weight. Even without the battery, the Bosch is a beefy 10.13 pounds. With the 8 Ah battery, the trimmer weighs 12.45 pounds—more than double the weight of some of the other models I tested, such as the Worx WG170.If you're using it for short periods, the weight may not bother you, but the whole point of a long battery life is that you can work for a longer stretch of time. I found the weight noticeable after about 10 to 15 minutes of use, after which I began to feel back strain as I worked.For context, I’m a moderately fit middle-aged man, accustomed to physical labor. I think Bosch would have been well served to include a shoulder strap with this string trimmer. Instead, I recommend that anyone using this string trimmer pick up at least an inexpensive shoulder strap online. For about $10, you can save yourself a lot of back pain.Also worth noting: The Bosch trimmer has a durable build. Part of my evaluation is a drop test, letting the tool fall onto concrete from typical usage height—in this case, from about waist height.If you're using outdoor power tools for any length of time, sooner or later that tool will fall off a wheelbarrow, tip over in the garage, or otherwise strike the ground. While testing, I noticed the Bosch had a warning label on the trimmer stating that it should never be used after being dropped. I suspect that the warning is there due to its weight. More weight means more momentum when the tool strikes the ground, and the Bosch certainly hit the concrete hard. But it didn’t seem to suffer any permanent damage, besides surface scuffs to the battery and case, and I continued to use it in my testing without any issue.Dan StoutReplacement string is fed through the head and wound around the robust spool by just cranking the head. The line feed is labeled so you won’t need to open the head to reload string, as you might have to with older models or budget trimmers.Who Should Buy This String Trimmer?If you have a large yard, hard-to-reach areas, or many smaller sections to trim, then the Bosch GRT18V is the right tool for the job. The generous 8 Ah battery ensures a long runtime, and the long length makes it possible to access hard-to-reach areas between trees or under bushes to ensure a tidy yard. Yes, it’s heavier than I’d like for a string trimmer, but that’s an issue remedied with a shoulder strap.That doesn’t mean this string trimmer is the right choice for every job. If you want a lighter-weight option, try the Worx WG170. Or if you want one with more pure cutting power, consider the DeWalt DCST972X1. But if getting through all your yardwork in one pass is what matters most, the Bosch is the best tool you can have on hand.Shop the Bosch GRT18V-40N18X String TrimmerOther String Trimmers We RecommendHusqvarna 110iL FLXi String Trimmer and EdgerThe Husqvarna 110iL can accept a range of heads, allowing it to serve as an all-in-one tool—perfect for homeowners with limited storage space.Worx Cordless 20V WG170 12-Inch String TrimmerA great value, the Worx is lightweight, compact, and portable. Its button-activated feed makes it easy to keep the string at the proper length during use.EGO Power+ 16-Inch Line IQ String TrimmerNow 17% OffThe EGO has one of the simplest reloading systems on the market. Slip a length of string through the inlet, press a button, and watch it wind onto the spool.A former residential remodeler and maintenance manager, Dan Stout has worked in nearly every part of the construction and DIY industry, from project planning and permitting to plumbing, drywall, carpentry, and more. He loves to write about the weird history of everyday objects, and to help readers make informed decisions about their homes.Jamie, Senior Reviews Editor, joined the Hearst Enthusiast Group in 2021. She has covered technology and consumer lifestyle gadgets since 1995—and shared her expertise in print, digital, and in broadcast originating the role of The Gizmo Girl for ESPN’s Cold Pizza. She has written about, tested, and reviewed everything from turkey fryers to high-definition TVs. Her byline has appeared in TWICE, Sound & Vision, Consumer Reports, and many others. In her free time, Jamie is in a yoga class, searching for the perfect matcha latte, or walking the boards.