String trimmer or edger: do you actually need both?

The shop will sell you both. The honest answer is that most people need one and a half, and which half depends entirely on whether you want a tidy line or a defined trench. Here is what each tool publishes, and where the overlap actually is.

The short answer

Two different machines pretending to be one

The row that settles the argument is depth control. A trimmer has none. You can hold it steady for ten feet; over forty feet along a driveway the line wanders, and the result reads as a fuzzy boundary rather than an edge.

The case for the edger

The edger cuts to a set depth and a trimmer cannot: EGO publishes an adjustable 3 inch depth on a guide wheel, set with a knob rather than a tool, and an IPX4 weather rating that is rare in this category and reasonable for a tool run along wet path edges. The current EA0820 adds a carbon fiber shaft with a lifetime warranty when registered within 90 days.

What it no longer gives you is a runtime you can plan against. The EA0800 this attachment replaced published a figure for every pack size in the range, which was enough data to show the draw is flat and that minutes scale with the pack you fit.

#ad Check the EGO Power+ 8" Carbon Fiber Edger Attachment EA0820 price on Amazon — how we're funded.

The case for using the trimmer you own

The EA0820 has one enormous asterisk: it is an attachment. No motor, no battery mount, no use whatsoever without an EGO PH1400 or PH1420 power head. If you are not already on the EGO multi-head system, buying a power head plus an attachment to edge one path is a strange way to spend money.

Against that, a decent trimmer edges perfectly acceptably. The EGO ST1521S has a split shaft and dual-feed 0.095 in line; the Ryobi RY402110 adjusts its swath from 15 to 17 inches and publishes 67 minutes. Both will cut a clean line along a path if you take your time and use the technique in how to edge a lawn.

#ad Check the EGO Power+ 15" POWERLOAD Carbon Fiber ST1521S price on Amazon — how we're funded.

Which one, by situation

• Short path, twice a year: trimmer. Buying a second tool for twenty minutes of annual work is not a good trade.
• Long driveway plus bed borders: edger. Consistency over distance is exactly what the guide wheel exists for.
• You already own an EGO power head: edger attachment, easily. It is the cheapest way to add a genuinely different capability to a platform.
• You own no cordless yard tools yet: trimmer first. It does more jobs, and edging is the one it does second-best rather than not at all.
• Overgrown boundary that has never been edged: trimmer to knock the growth back, then the edger to cut the line. This is genuinely a two-tool job.

#ad Check the Ryobi 40V HP Whisper 17" Carbon Fiber RY402110 price on Amazon — how we're funded.

The middle path most people should take

Buy the trimmer first and use it for both jobs for a season. If the edge annoys you — if you keep looking at a wandering line along the drive — add the edger, and by then you will already own the pack and the power head that makes it cheap. That sequencing is the whole argument for the multi-head system, and it is the same logic as our first yard tool kit buying order.

What we cannot tell you

We have not used either tool. How clean an edge an 8 inch blade cuts in root-bound soil, how much the guide wheel wanders on a broken path, and how a trimmer's line holds up cutting against concrete are all things a spec sheet does not address.

What the specs do settle is the structural difference: 3 inches of adjustable, guided depth on one side and a wrist on the other. Decide whether you need the depth, and the rest follows.