Choosing a cordless string trimmer in 2020 feels like picking through a maze of voltage numbers, battery platforms, and marketing hype. I’ve tested over 60 outdoor tools in the past five years, and let me tell you – not all 40V trimmers are created equal, and a 20V that costs twice as much isn’t automatically better. This guide will help you cut through the noise and find the right tool for your yard, your budget, and your sanity.
Why Your Choice Matters
A bad trimmer can make a simple 15-minute edge job feel like an hour of frustration. I’ve fought with underpowered motors that stall in thick grass, bump heads that jam constantly, and batteries that die after three fence lines. A good trimmer, on the other hand, starts every time, runs long enough to finish the job, and doesn’t leave your arms vibrating for hours. The key is understanding what actually matters in a cordless string trimmer – not just the price tag or the flashy RPM number on the box.
Key Features Explained
Voltage & Power: What You Actually Need
The voltage battle is the first thing you’ll run into. 20V (or 18V) trimmers are lightweight, great for small yards under a quarter acre. They’re easy on the wrists and often cheaper. But they lack torque – if you have thick crabgrass or overgrown edges, you’ll be fighting the head. A 20V string trimmer works fine for light maintenance, but don’t expect it to power through heavy brush.
Stepping up to 40V is where most homeowners should land. These trimmers deliver a sweet spot of power and weight. They can handle moderate weeds, edging along driveways, and even some light brush. I’ve used a 40V unit that easily took down six-foot tall goldenrod without bogging down. For anyone with a medium yard (quarter to half acre), this is the voltage to target. Read our 40V string trimmer buying guide for more details.
Then there’s 60V and above. These are heavy, expensive, and built for large properties or commercial use. They offer real torque and can run a brush cutter attachment. But unless you have an acre or more, you’re paying for weight you don’t need. The motor design matters more than raw voltage – a well-engineered 40V brushless motor can outperform a cheap 60V brushed one. Pay attention to brushless vs. brushed motors; brushless is more efficient and lasts longer.
Cutting Width & Line Feed
Cutting width (typically 12 to 18 inches) determines how fast you can work. Wider is faster but requires more power and can be heavier. For most residential edges, 14-16 inches is ideal. Too wide and you’ll struggle in tight spots; too narrow and you’ll be making extra passes.
Line feed systems are surprisingly critical. Bump feed heads are reliable – you tap the head on the ground to advance line. They work when you need them, but they can be finicky if the line welds together in the spool. Auto feed (or automatic feed) heads advance line without tapping – nice for staying in the groove, but they can overfeed and waste line. Some models offer a “Tap & Go” hybrid. For beginners or elderly users, I recommend a bump feed with a large opening that’s easy to reload. Check out brushless string trimmers for models with reliable feed systems.
Line diameter also matters. 0.065-inch line is fine for light grass. For thicker weeds, step up to 0.080 or 0.095. Make sure the trimmer you buy can accept the thicker line – many budget models are limited to thin line, which will break constantly.
Weight & Ergonomics
Weight is more than the number on the spec sheet – it’s about balance. A 9-pound trimmer that’s balanced well feels lighter than a 7-pound head-heavy one. Look for a trimmer with the battery mounted under the handle (like many 40V models) rather than at the very top. That lowers the center of gravity and reduces arm fatigue.
Shaft design: straight shaft gives you more reach under bushes and is better for edging (you rotate the head 90 degrees). Curved shaft is lighter and easier to maneuver for shorter users, but harder to edge with. Straight shaft is the standard for most serious users. Handle design also varies – a D-handle (loop) offers great control, while a bike-handle (like a bicycle grip) can be more comfortable for long sessions. If you have arthritis or are elderly, consider a lightweight model – see our best trimmers for elderly guide.
Battery System & Runtime
Battery voltage is only half the story; amp-hours (Ah) determine runtime. A 40V 2.5Ah battery stores 100 watt-hours. A 40V 5Ah stores 200 watt-hours. More Ah = longer runtime, but also more weight and cost. For most jobs, a 4Ah battery is sufficient for a medium yard.
Charger speed matters too. A 30-minute charger is a luxury, but a 2-hour charger is common. If you have a large yard, buy a second battery and a fast charger. Also consider ecosystem lock-in: once you buy into a brand’s battery platform, you’re likely to stick with it for other tools (leaf blowers, chainsaws). Brands like DeWalt and Milwaukee have extensive 20V and 60V lines; Ego has a strong 56V platform; Ryobi’s 18V/40V system is budget-friendly. Evaluate the full system before committing. For budget-conscious buyers, check trimmers under $100.
Top Brands Compared
Here’s a quick snapshot of major contenders as of 2020. This isn’t exhaustive, but it covers the ones I see most often in real yard use.
Ego Power+ – Their 56V platform is the gold standard for residential use. Excellent power, build quality, and battery life. The trimmer is heavy but well-balanced. Pricey, but worth it if you have the budget.
DeWalt – Their 20V MAX trimmers are solid for light work, but the 60V FlexVolt trimmers are beasts. The battery system is versatile (20V/60V). Build quality is good, but you pay for the name.
Milwaukee – Similar to DeWalt: M18 trimmers are adequate for small yards; M18 Fuel (brushless) is better. Heavy but powerful. Best for those already in the Milwaukee ecosystem.
Ryobi – The 40V brushless trimmer is a fantastic value. Reliable, decent power, and batteries are affordable. Ideal for homeowners on a budget who want to expand into other tools. Not as refined as Ego, but hard to beat for the price.
Black+Decker – Their 20V MAX trimmers are entry-level, fine for tiny yards. Build quality is so-so, and line feed can be frustrating. Cheap, but you get what you pay for. See our best string trimmers page for more detailed comparisons.
Worx – Known for innovative features like the “Worx AutoWheel” and “Worx 40V PowerShare” system. Their trimmers are lightweight and affordable, but power is average. Good for small to medium yards.
Our Recommendations
Best Overall: Ego Power+ ST1500SF. 56V, 15-inch cut, brushless, carbon fiber shaft, variable speed. Powerful, quiet, and comfortable. If you can swing the price, this is the one to beat.
Best Value: Ryobi 40V Brushless (RY40270). Around $150 bare tool, takes the excellent 40V battery. Reliable feed, good power for medium yards, and Ryobi’s battery ecosystem is huge. A no-brainer for most homeowners.
Best for Small Yards: DeWalt 20V MAX (DCST922). Light, easy to handle, and the 20V battery is common. Not for heavy weeds, but perfect for quick edges.
Best Lightweight Option: Worx WG163 (18V). Curved shaft, under 7 pounds, surprisingly good for the price. Great for elderly users or those with small lots.
Best for Budget: Black+Decker LSTE525 (20V). Under $70 with battery. It’s basic and the line feed is mediocre, but it works for trimming grass in a city lot. Manage expectations.
FAQ
Q: Is a 40V trimmer powerful enough for heavy weeds? Yes, most 40V brushless models can handle thick weeds like poison ivy or small brambles. For serious brush, go 60V.
Q: Can I use a weed eater as an edger? Yes, if the head rotates 90 degrees. Many straight-shaft trimmers have a rotating head. Curved shaft trimmers usually don’t.
Q: How long does a 40V 4Ah battery last? In real use, about 30-45 minutes of continuous trimming. That’s enough for a typical half-acre yard if you’re efficient.
Q: What line should I use? For most trimming, 0.080-inch is a good all-around diameter. For heavy weeds, step up to 0.095. Use twisted line for more cutting power.
Q: Are battery trimmers quieter than gas? Significantly. A good cordless trimmer is about 85 dB – similar to a vacuum cleaner. Gas trimmers are 95-100 dB and require ear protection.
Q: Do I need a brushless motor? Yes, if you can afford it. Brushless motors are more efficient, run cooler, and last longer. They also provide more torque without extra weight. The price premium is worth it.
Q: Should I buy a trimmer with battery included or tool-only? If you already own batteries from the same brand, buy tool-only. Otherwise, get a kit – batteries and chargers are expensive separately. For details, see long-runtime trimmers.
Buying a cordless string trimmer is a long-term investment in your yard care routine. Focus on voltage that matches your property size, a brushless motor, and a battery system you can build on. Don’t get seduced by the highest RPM number – a 1500 RPM 40V brushless trimmer will outcut a 2000 RPM 20V brushed one any day. Measure your yard honestly, set a realistic budget, and choose a trimmer that’s built to last. I’ve seen too many people regret a cheap purchase within a month. Spend a little more upfront, and you’ll be happy for years.
