EGO Power+ Powerload ST1521S Review

My First Month with the EGO Power+ Powerload ST1521S: A Real-World Test from a Lawn Pro

After nine years running a lawn crew, I’ve handled more string trimmers than I can count-from cheap gas models that vibrated my hands numb to high-end commercial units that cost more than my first truck. When I started testing trimmers on my own property for YardToolLab, I knew the EGO Power+ Powerload ST1521S had big expectations to meet. It’s our “Best Overall” pick, but I wanted to see if it held up to the daily abuse of real grass, weeds, and the occasional fence-line jungle. So I bought one (battery and charger separate, which I’ll get to) and put it through the wringer on my half-acre lot for a solid month. Here’s the honest, sweaty truth.

How I Tested It

I didn’t baby this thing. My property has a mix of manicured Bermuda grass in the front, a patchy back lawn that loves clover and crabgrass, and a fence line along the alley where weeds grow chest-high by July. I also have a ditch that collects morning glory vines and thistles, plus a rock garden edge where I need precision. Over four weeks, I used the ST1521S for weekly trimming, edging along sidewalks and driveways, and heavy-duty clearing of that fence-line monster. I deliberately let the grass grow an extra week in one spot to test the cutting power under load. I also ran the battery down to zero multiple times to gauge runtime, and I tried to jam the Powerload auto feed by running it through thick, wet weeds. Every session I noted arm fatigue, balance, and how often I had to stop to fix line feed issues.

Cutting Power and Line Feed

Let’s start with the heart of the matter: the 56V battery and the dual-feed spiral twist 0.095-inch line. I was skeptical at first. I’ve used plenty of cordless trimmers that bog down in thick grass, leaving you with a half-chewed mess. The ST1521S? It chewed through that fence-line grass like it was butter. I’m talking stalks as thick as a pencil, mixed with bindweed and wild blackberry canes. The trimmer didn’t stall once. The 15-inch cutting swath is wide enough to cover ground fast, but not so wide that it feels clumsy in tight spots. I cleared a 50-foot stretch of overgrown alley in about 10 minutes-a job that usually takes 20 with my old gas trimmer.

The Powerload auto line feed is the feature I was most curious about, because I’ve had nightmares with bump-feed heads that jam or over-spool. EGO’s system uses a button on the head that you press to advance line automatically. No banging the head on the ground, no guessing. The first time I used it, I pressed the button while the trimmer was running, and about an inch of fresh line popped out. It worked perfectly every time for the first two weeks. Then, during a heavy weed session, I hit a thick patch of wet morning glory vines. The line snapped off short, and when I pressed the button, nothing happened. I thought it was jammed. I stopped, pulled the head apart, and found the line had wrapped around the spool wrong-user error, probably because I tried to force-feed it while the head was spinning too fast. After I re-spooled it carefully (the manual recommends feeding the line through the eyelets while the head is stationary), it worked flawlessly again. No jams after that, even in tall, wet grass. The dual-feed design gives you two cutting edges, which really helps with edging-I can run the trimmer along a sidewalk and get a clean, straight cut without tilting the head awkwardly.

One thing I noticed: the 0.095-inch line is thicker than what most homeowner trimmers use (usually 0.080). It lasts longer and cuts better, but it does make the trimmer slightly louder when it hits concrete or rocks. That’s a trade-off I’m happy with. I’d rather replace line less often than have a whisper-quiet trimmer that snaps every five minutes.

Battery and Runtime

Here’s the elephant in the room: the battery and charger are sold separately. I already owned a few EGO batteries from other tools, so I had a 2.5Ah and a 5.0Ah pack. On a full charge with the 5.0Ah battery, I got about 45 minutes of continuous heavy trimming-mixing cutting thick weeds and regular lawn edging. That’s enough to do my entire property (about 0.3 acres of trim-able area) with some battery left over. The 2.5Ah pack gave me about 20 minutes, which is fine for quick touch-ups but not for a full yard. If you’re buying this as your first EGO tool, factor in the cost of at least one 5.0Ah battery and a charger. It stings upfront, but the power is worth it.

I did run into one issue: the battery indicator lights on the pack are hard to see in direct sunlight. I had to shade the battery with my hand to check the charge level. Also, the trimmer doesn’t have a low-battery warning beep or vibration, so I’ve been caught off guard when it just stops mid-swing. That’s a minor annoyance, but I’ve learned to keep a spare battery in my pocket. On the plus side, the battery charges in about 50 minutes on the fast charger, so I can swap and keep going without a long break.

Handling, Balance, and Comfort

This is where the ST1521S really shines for me. I’ve used gas trimmers that weigh 12-14 pounds, and after an hour, my shoulders and forearms are screaming. The EGO with a 5.0Ah battery weighs around 10 pounds, but the balance is so good it feels lighter. The handle is adjustable, and I set it to a comfortable angle for my height (6 feet). The grip is soft rubber, not that hard plastic that gives you blisters. I trimmed for two straight hours one Saturday-edging the driveway, cleaning up the fence line, and trimming around flower beds-and my arms were tired, but not sore. No numbness in my fingers, no backache from leaning over.

The trigger is a variable-speed switch, so you can feather the throttle for delicate work like trimming around a birdbath or go full power for heavy weeds. I liked that control. The guard is small but effective-it kept debris off my legs without blocking my view of the cutting head. One nitpick: the shaft is a fixed length. I’m tall, so it’s fine, but a shorter person might find it a bit long. Also, the head doesn’t tilt for edging; you have to rotate the whole trimmer. That’s standard for most cordless models, but some gas trimmers have a rotating head. I got used to it after a few passes.

Who Should Buy It

After a month of hard use, I can say the ST1521S is perfect for homeowners who want gas-level power without the hassle of mixing fuel, pulling cords, or dealing with carburetor issues. If you have a quarter-acre or more, or if you deal with thick weeds and tall grass regularly, this is a solid investment. It’s also great for people who already own EGO tools and have batteries-you’re just buying the trimmer head. But if you’re on a tight budget and only have a tiny postage-stamp lawn with thin grass, you might be fine with a cheaper corded or smaller cordless model. The upfront cost (trimmer plus battery and charger) is higher than a basic gas trimmer, but over a few years, you’ll save on gas, oil, and maintenance.

I wouldn’t recommend it for commercial crews who trim eight hours a day. The battery runtime just isn’t there for that kind of workload, and you’d need three or four spare packs. But for a dedicated homeowner who takes pride in their yard? Absolutely.

My Verdict

I went into this test expecting a good trimmer, but the ST1521S surprised me. The cutting power is genuinely impressive-it never bogged down in grass that would choke a 30cc gas trimmer. The Powerload auto feed, after my initial spooling mistake, worked flawlessly and saved me the hassle of bumping the head every few minutes. The balance and comfort made it a joy to use for longer sessions. Yes, the battery and charger being sold separately is a pain, and the price tag stings at first. But after using it for a month, I’d pay it again. My gas trimmer is now gathering dust in the shed. This EGO is staying in my truck.

If you’re on the fence, here’s my honest advice: buy the ST1521S as part of a kit with a 5.0Ah battery and charger. You’ll get the best experience, and you’ll wonder why you ever put up with gas fumes and pull cords. For my yard, it’s the best string trimmer I’ve ever owned.