In-depth review
EGO Power+ ST1521S Review
A detailed review of the EGO Power+ ST1521S string trimmer: Powerload head, Line IQ feed, and 15-inch cutting performance.
EGO EGO Power+ ST1521S
15-inch Powerload head with automatic line loading.
Our verdict
The ST1521S earns its premium price on the head alone: the Powerload auto-winding system and Line IQ automatic feed eliminate the two chores every trimmer owner hates. The trade-off is weight and cost; it is the heaviest and most expensive model here, and small-yard owners will not use its 15-inch swath.
What we like
- Powerload head winds trimmer line automatically, eliminating manual spool rewinding
- Line IQ technology senses the load and feeds the correct line length without bumping
- 15-inch cutting swath with 0.095-inch dual line handles thick grass and weeds
- 56V ARC Lithium platform is shared across EGO blowers, mowers, and hedge trimmers
What to watch out for
- Heavier and pricier than 20V-class trimmers
- Best performance requires the larger 4.0Ah battery, which adds weight
- Overkill for small yards under a quarter acre
Who it is for
Homeowners with medium to large yards who trim weekly and want to spend their time cutting, not feeding and rewinding line.
Powerload and Line IQ: the head is the product
EGO's Powerload head is the ST1521S's defining feature. You thread the line through the head and press a button; the head winds it for you, a process that takes seconds versus minutes of manual spool winding. Line IQ then monitors the load and feeds line automatically as it wears, so the trimmer never runs short mid-pass. Published reviews from This Old House and Popular Mechanics both single out the head design as the reason the EGO outclasses bump-feed rivals on ease of use.
Cutting performance
The documented numbers are strong: a 15-inch cutting swath, 0.095-inch dual line, and a 56V ARC Lithium motor. That combination puts it at the top of this guide on both width and line thickness. The 0.095-inch line is rated for weeds and thick grass that would shred the 0.065-inch line on budget trimmers. The 56V platform also powers EGO mowers and blowers, so the battery investment carries across the yard lineup.
Weight and handling
The price of the 56V platform is weight. With the battery installed, the ST1521S is noticeably heavier than 20V-class trimmers, and long sessions will tire smaller users. EGO ships it with a shoulder strap, which helps, but buyers with small yards should weigh whether the extra power is worth carrying.
How it stacks up
Against the DeWalt DCST922B, the EGO wins on swath (15 vs 13 inches), line thickness (0.095 vs 0.080 inch), and feed system (automatic vs bump feed), but loses on platform cost if you already own DeWalt 20V batteries. Against the Black+Decker LST140C, the EGO's 56V motor outclasses the 40V platform on torque, though both offer 13-plus-inch swaths; the Black+Decker is the cheaper path to mid-power trimming.
What owners report
Commonly praised
- Power that owners compare to gas trimmers, without fuel mixing or pull cords
- One battery finishes a typical suburban yard
- Quiet enough to use early in the day
Common complaints
- Old line can get stuck inside the head and needs disassembly to clear
- Reloading line is not as easy as the marketing suggests
- It feels heavy on the shoulders during long sessions
Recurring themes from owner reviews on retailers and forums, summarised by our editors. Updated October 2026.
Key specifications
- Voltage platform
- 56V ARC Lithium
- Cutting swath
- 15 inches
- Line diameter
- 0.095 inch dual line
- Line feed
- Powerload auto-wind + Line IQ
- Head type
- Bump-feed free, automatic
Also consider
DeWalt DeWalt 20V Max DCST922B
13-inch dual-line trimmer on the 20V Max platform.
- Voltage platform: 20V Max
- Cutting swath: 13 inches
Worx Worx WG163
12-inch 2-in-1 trimmer and edger at a budget price.
- Voltage platform: 20V Power Share
- Cutting swath: 12 inches
Research-based assessment. ThePickLedger has not hands-on tested this product; this evaluation synthesizes manufacturer specifications, retailer documentation, and published expert reviews.
Questions, answered
Does the Powerload head really wind line automatically?
Yes. Per EGO's documentation, you feed the line through the head and press the load button; the motor winds it. It replaces manual spool disassembly and rewinding.
What batteries does it use?
EGO 56V ARC Lithium batteries, shared with EGO's mowers, blowers, and hedge trimmers. Runtime depends on battery amp-hours; the larger 4.0Ah and up packs suit bigger yards.
Is it too heavy for a small user?
It is the heaviest model in this guide. EGO includes a shoulder strap, but users under about 5-foot-4 or those with shoulder issues should consider the lighter DeWalt or Worx options.