40V vs 20V vs 80V String Trimmer: Which Voltage Is Right for You?

20V suits small yards and light trimming, 40V is the balanced pick for most homeowners, and 80V is the go-to when grass gets thick.

For the full breakdown, see our best 40V Trimmer guide.

The big number on the box tells you less than you think. Three trimmers can all print “40V” and still cut like different machines, because voltage is one factor sitting beside cutting swath, line thickness, amp-hours, and runtime. Voltage sets the ceiling on how hard a motor can work; the rest decides what that power feels like in your hands.

Here’s the short version for most US lawns. A 20V trimmer handles edges and thin grass. A 40V trimmer covers the middle ground — enough muscle for thicker grass and larger yards without the weight and cost of a bigger system. An 80V trimmer is the heavy-duty category, built for bigger properties and stubborn growth. Pick the category first, then check the specs that actually matter.

What Each Voltage Actually Does On Your Lawn

Only one category fits each kind of yard, and matching it matters more than chasing the highest number. A bigger battery on a trimmer you rarely use is money and wrist strain you don’t need to spend.

20V fits light-duty trimming and small yards. Edging a walkway, cleaning up around a mailbox, and refreshing a postage-stamp lawn sit right in this range. The tools are usually the lightest of the three, and the batteries often share a platform with drills, blowers, and other tools you already own.

40V is the common homeowner sweet spot. It adds real power for thicker grass and larger yards while staying lighter, cheaper, and simpler than an 80V system. WORX, for instance, builds its WG184 trimmer around two 20V Max Power Share batteries running together for “40V of total power and performance,” and the same battery family powers 75+ tools across its 20V, 40V, and 80V line.

80V is the strongest category. If your property is large, the grass runs thick and wet, or you’re clearing overgrowth along a fence line, this is the class built for it. The trade is weight, price, and a bigger battery to charge.

The Specs That Decide More Than Voltage

Voltage alone won’t tell you how a trimmer performs. Four other numbers do the heavy lifting, and two trimmers at the same voltage can differ widely on all four.

One trap worth naming: a “40V” label isn’t always a single 40V battery. WORX’s WG184 hits 40V by pairing two 20V packs, while other brands may use one 40V pack. The performance can be similar, but the batteries and chargers are different animals. Battery ecosystems are also brand-specific — WORX markets compatibility only inside its own Power Share family, so a battery from one brand won’t fit another.

Once you know which class fits your yard, the next step is comparing real models on swath, amp-hours, and runtime rather than the voltage badge. Our rundown of the best tested 40V trimmer options is a good place to start.

Running And Maintaining A Cordless Trimmer

Battery-powered trimmers reward a couple of simple habits. Most of what goes wrong traces back to how the battery is handled, not the trimmer itself.

On the 40V Greenworks STF312, the sequence runs like this. Align the ribs and grooves on the battery, then push until it locks with a click. To remove it, press and hold the battery release button. To start trimming, push the lock-out button and pull the trigger. Switch between low and high speed with the speed switch. When the line runs short, tap the trimmer head against the ground while it’s running and the auto-feed advances fresh line.

Two safety points come straight from the manufacturer’s manual. Never install or remove the battery while the motor is running — stop the machine and wait for the motor to fully stop first. And if the battery pack or charger is damaged, replace it rather than keep using it. Keep an 80V or 40V battery indoors through winter and it’ll hold up better across seasons.