Ego Power+ ST1521S 15-inch string trimmer review: light and easy trimming

Hi-tech string trimmer includes carbon fiber and long battery life

Ego Power+ ST1521S string trimmer review
(Image credit: Ego)
T3 Verdict

The Ego Power+ ST1521S is a hi-tech strimmer that is light, easy to use and has decent battery life.

Reasons to buy
  • +

    Effective cutting

  • +

    Well balanced in use

  • +

    No line tangles

Reasons to avoid
  • -

    Can’t be taken apart for storage

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The Ego Power+ ST1521S is a hi-tech string trimmer, boasting a big battery, lightweight carbon fiber shaft, and a Powerload automatic string loading system. Most of this fancy stuff is worth it; it is easy to use and cuts well, but the Powerload system is not as easy to use as they claim.

Ego Power+ ST1521S 15-inch string trimmer review: design and build quality

I was impressed with the overall build quality of the Ego Power+ ST1520S, which requires just eight screws to assemble. It ships folded into two halves, but the halves fit together with a single screw for use. This can’t be taken apart or folded for storage without a screwdriver, which is a pity, as this would make the six-foot-tall string trimmer a lot easier to carry and store. Ego Power+ does offer another version with a telescoping aluminum shaft (the ST1511T).

The ST1521S is powered by a large 56V, 2.5 Amp-hour battery that is physically the biggest of those that we tested but has the smallest capacity. This battery weighs 2.9lbs on its own (1.3kg) and clips onto the top of the trimmer. Ego says that you can use this battery across all its products. The same battery will work on their leaf blowers, mowers and snow blowers, and there is even a portable power station that can run your 110V home appliances in a power outage. That makes the battery pretty flexible as long as you have (or buy) other Ego Power+ devices. Unfortunately, that range doesn’t include one of the major users of rechargeable batteries: power tools.

The included 2.5 Ah Lithium-Ion battery takes just under an hour to charge and runs the trimmer for about 40 minutes in our tests. Although it may be smaller than most, it lasted pretty much the same amount of time in use. Ego offers some much larger batteries in its range, up to the 10Ah honker that is designed to drive power-hungry devices like their electric snowblower.

The Ego Power+ ST1521S is rather heavy at just over 10lbs (4.5kg) including the battery, but it is well balanced between the motor at one end and the battery at the other, so it doesn’t feel too heavy in use. The elbow naturally falls on top of the battery holder, providing a good way to brace the weight. The handle is also adjustable, which helps you to find the right balance point for comfortable use. Still, it is a big, bulky trimmer that I found I had to keep swapping between my left and right side to remain comfortable when using it for a longer period.

The speed control of the Ego Power+ ST1521S falls naturally under the index finger, with a safety switch under the thumb. The trimmer won’t start unless this safety switch is pressed down, so it will automatically stop if your hand slips. I did find this slightly irritating on occasion. It’s easy for the thumb to slip (especially if you are wearing gloves) which makes the trimmer stop without notice.

Ego Power+ ST1521S string trimmer review

(Image credit: Ego)

Ego Power+ ST1521S string trimmer review: performance and accessories

The Ego Power+ ST1521S trimmer’s 2.5Ah battery has the smallest capacity of the rechargeable string trimmers that I tested. The DeWalt, for instance, comes with a 9 Ah one that contains more than three times as much juice. Battery size isn’t the only thing that affects battery life, but it is a factor. I found that the Ego Power+ ST1521S lasted just under 40 minutes in my tests cutting through light vegetation: that’s pretty much the same as the DeWalt. You can also buy the string trimmer with a larger 5Ah battery, for $100 more.

The Powerload technology is nifty, but not quite as simple as the ads make out. It does make the process of loading the cutting line easier than most, but it isn’t hassle-free. It works like this: you get a pre-cut length of line (about 13 feet long) and feed it through the spool until you have equal lengths poking out of each side. Then you press the green power load button on top of the trimmer head, and the motor winds the line back, loading it onto the spool with a clackity-clank noise until there is just a short length sticking out of each side of the spool head. Then you are ready to start trimming.

It is definitely easier than trying to stuff a spool full of line into place, then quickly screwing the cover back on quickly before the spool pops out, but it still requires some effort. Plus, you still have to be careful: if you don’t get the line even when you start the process, you’ll waste part of the line as it will get cut off as soon as the trimmer starts up.

The line didn’t get tangled up or stuck in our test over several hours of trimming. During all of my tests of cutting vegetation light and tough, I had no problems with the Ego’s line getting tangled up inside the head or not spooling out when I bumped the head to release more line.

Ego Power+ ST1521S string trimmer review

(Image credit: Ego)

Ego Power+ ST1521S string trimmer review: Verdict

The Ego Power+ ST1521S string trimmer has it where it counts. It offers plenty of cutting power in a lightweight, easy to maneuver package. It is also decently priced. At around $220, it costs significantly less than the Husqvarna and DeWalt electric models.

Ego Power+ ST1521S string trimmer review

(Image credit: Ego)
Richard Baguley

Richard Baguley has been writing about technology since the 1990s, when he left a promising career in high finance to work on Amiga Format magazine for Future. It has been downhill for him ever since, writing for publications such as PC World, Wired and He has tested gadgets as diverse as 3D printers to washing machines. For T3, he covers laptops, smartphones, and many other topics. He lives near Boston in the USA with his wife, one dog, and an indeterminate number of cats.