EGO Power+ ST1521S Review: 56V PowerLoad String Trimmer

Why the EGO ST1521S stands apart

Most string trimmers are remembered for two things: how well they cut, and how much they frustrate you when the line runs out. The EGO ST1521S addresses both. Its 56V ARC Lithium brushless motor delivers cutting performance that suburban owners previously had to buy a gas trimmer to get, and the POWERLOAD head reduces line reloading from a five-minute wrestling match to a ten-second button press.

That combination is why the ST1521S has become the benchmark against which every residential battery trimmer is measured.

Platform and voltage: why 56V matters here

EGO built its outdoor power equipment line around a 56V nominal voltage — higher than Ryobi's 40V platform and Craftsman's 20V system. More volts is not always the right answer, but for a string trimmer it matters: higher voltage allows the brushless motor to maintain line tip speed longer before a brief sag under load. On normal lawn edges, all modern battery trimmers perform adequately. On overgrown grass, knee-high weeds, and the occasional ornamental grass clump, the 56V platform sustains speed more consistently.

The included 2.5Ah battery is honest about what it delivers — 30 to 40 minutes of mixed yard work. That covers most quarter-acre lots before needing a recharge. Owners with larger properties or who trim in sessions should budget for a second 2.5Ah pack or step up to the 5.0Ah battery, which is worth the added weight if your yard regularly consumes more than one battery.

The POWERLOAD head in practice

The most discussed feature of the ST1521S is POWERLOAD, and the praise is earned. Traditional spool replacement requires you to pull off the bump-feed head, find the correct line diameter, cut the right length, thread both ends through guides, wind in the correct direction without tangling, and reassemble without the spring bouncing across the garage floor. That sequence takes most homeowners 5 to 10 minutes and is where trimmer frustration peaks.

With POWERLOAD, you insert a pre-cut length of 0.095-inch line into the cartridge slot and press the button on the guard. The head winds the line onto the spool in about ten seconds. Pre-loaded replacement cartridges from EGO take even less time — drop in, lock, and go.

The caveat is cost: EGO replacement cartridges are roughly twice the price of generic bump-feed spools, and rural hardware stores sometimes stock only generic line. For most suburban homeowners shopping at Home Depot or Lowe's, this is not a problem in practice.

Weight and ergonomics

At 11.97 lbs with the 2.5Ah battery, the ST1521S is heavier than Ryobi's RY40250 (8.92 lbs) and noticeably heavier than the Craftsman CMCST930P1 (6.8 lbs). For a typical 20-minute session, this difference is barely felt. Over a long Saturday trimming a half-acre with significant edge work, the weight compounds. Owners with lower-back or shoulder concerns should either plan short sessions, use a shoulder strap (sold separately), or consider whether the lighter Ryobi kit covers their needs.

The carbon fiber straight shaft earns genuine praise. At 42 inches it reaches under shrubs, deck stairs, and raised garden beds cleanly, and the split-shaft design lets you remove the head-end for compact storage. EGO's lifetime warranty on the shaft — contingent on registering within 90 days of purchase — adds durable confidence that alloy-shaft rivals do not match.

Cutting performance across vegetation types

On standard lawn grass and moderate weeds up to ankle height, the ST1521S is decisive: the 15-inch cutting swath and 0.095-inch line clear cleanly in a single pass, and variable speed control lets you conserve battery on fine edging before throttling up for taller growth.

On overgrown summer grass and ornamental clumps, the 56V platform shows its advantage over 40V competitors. Line speed drops less on the first impact through dense growth, meaning fewer stalls and more consistent cuts per pass. Against a well-tuned gas trimmer on the same vegetation, the performance gap is small enough that most homeowners would not notice it.

For heavy brush — saplings thicker than a pencil, blackberry canes — the ST1521S handles occasional incursions but is not built as a brush-cutter. The carbon fiber shaft is not designed for brushcutter blade attachments; that category belongs to full attachment-head platforms.

Value in the battery trimmer segment

At $229 for the kit with the 2.5Ah battery and charger, the ST1521S costs roughly $50 more than the Ryobi RY40250 kit with a larger 4.0Ah battery. That premium buys the 56V voltage advantage, the POWERLOAD head, the carbon fiber shaft warranty, and the 5-year tool warranty — versus Ryobi's 5-year tool warranty but no shaft warranty or auto-load head.

Against the Craftsman CMCST930P1 — a 20V brushless kit that prices around $130 — the EGO is a tier above in both performance and price. The Craftsman covers small yards with competence; the EGO covers larger, harder yards with authority.

Against the DeWalt DCST972X1 at $349, the EGO is the better value for pure trimming use. The DeWalt's 60V FLEXVOLT platform, 17-inch swath, and attachment capability justify the premium for users who want to swap in a brushcutter head. For trimmer-only duty, the EGO delivers equivalent results for $120 less.

Final assessment

The ST1521S has earned its position as the category benchmark because it removes the two most consistent complaints about cordless string trimmers: inadequate power and tedious line changes. Its 56V platform is the closest battery equivalent to gas for residential use, and POWERLOAD makes the tool genuinely pleasant to maintain. Weight is the real trade-off to understand before buying. For the buyer who wants the best all-around battery string trimmer without attaching other yard tool heads, the ST1521S is the right choice.