Trimmers & Edgers
String trimmer voltage: what 40V, 56V and 80V actually mean
The longest-running trimmer we hold specs for is the 40V machine. Voltage is not the number you are looking for.
Affiliate disclosure: we earn a commission if you buy through our links, at no extra cost to you. It never changes which product we rank first — here is how we're funded.
We have not tested these units. Every spec on this page comes from the manufacturer's own documentation and is linked to it. Every computed figure is arithmetic you can redo. Prices are checked daily — last verified January 1, 1970. Here is exactly how we pick.
Voltage is the biggest number on a trimmer box and one of the least informative. Here is the test: in our registry, the trimmer with the longest published runtime, the widest swath and the best energy efficiency is the 40V one. The 80V machine is second on two of those and last on the third.
The short answer
Watt-hours explain runtime; voltage does not
The energy ratio and the runtime ratio agree to within one percent. The voltage ratio is inverted. That is as clean a demonstration as the published specifications allow, and it is the reason we work in watt-hours throughout this site — see watt-hours explained.
What voltage does actually govern
- Which packs fit. This is the real consequence, and it is permanent. A 40V tool takes 40V packs and nothing else.
- Current for the same power. Higher voltage delivers a given wattage at lower current, which means thinner conductors and less heat. That is an engineering benefit, not a specification you can read off a box.
- Pack size for the same energy. An 80V 2.0Ah pack and a 40V 4.0Ah pack hold the same 160Wh. The 80V one is not smaller or lighter for it in any published figure we hold.
- Nothing about swath, line gauge or head type. Those are design choices made independently of the battery.
Three platforms, three trimmers
| Spec | RYOBI 40V RY402110 | Greenworks 80V ST80L210 | EGO 56V ST1521S |
|---|---|---|---|
| Nominal voltage | 40V | 80V | 56V |
| Pack in the kit | 6.0Ah | 2.0Ah | 2.5Ah |
| Watt-hours | 240Wh | 160Wh | 140Wh |
| Claimed runtime | Up to 67 min | Up to 45 min | Up to 30 min |
| Energy per minute | 3.58Wh/min | 3.56Wh/min | 4.67Wh/min |
| Swath | 15-17 in | 16 in | 15 in |
| Motor speed | Not published | 6200 RPM | Not published |
| Line | 0.095 in | 0.080 in | 0.095 in |
| Recharge | Not published | 30 min | 50 min |
| Warranty | Not published on this page | 3-yr tool / 4-yr battery | 5-yr tool / 3-yr battery |
Transcribed from the RY402110, ST80L210 and ST1521S product pages. Watt-hours and energy per minute are our arithmetic.
The three, and who each is for
The RYOBI is the large-yard answer on published figures: most energy in the kit, longest claimed runtime, widest adjustable swath.
#ad Check the Ryobi 40V HP Whisper 17" Carbon Fiber RY402110 price on Amazon — how we're funded.
The Greenworks is the lightest at 7.1 lb bare and recharges in a published 30 minutes, which is shorter than its own 45 minute runtime — two packs make it continuous.
#ad Check the Greenworks 80V 16" String Trimmer ST80L210 price on Amazon — how we're funded.
The EGO is the best-equipped tool: POWERLOAD winding, a carbon fiber shaft with a lifetime warranty and a five-year tool warranty. Buy it with a bigger pack than the kit supplies.
#ad Check the EGO Power+ 15" POWERLOAD Carbon Fiber ST1521S price on Amazon — how we're funded.
How to actually choose
- Start from the platform you already own. If you have four 40V packs, a 40V trimmer is right regardless of what an 80V spec sheet says.
- Multiply volts by amp-hours on the pack in the kit. That is the number to compare, and it is the number nobody prints.
- Check the recharge time against the runtime. A charger faster than the tool's runtime plus a second pack is continuous operation.
- Then look at swath and line gauge. Those matter, and they matter less than the two figures above.
The same argument applied across every tool class is in 40V vs 80V, tool by tool.
What we cannot tell you
We have not metered any of these trimmers. Runtime claims are the makers' own, with no published test conditions — grass type, speed setting and line length all change the answer and none of them are stated. Only Greenworks publishes a motor speed, so cutting-power comparisons between the three are not possible from published data.
The products discussed
Specs are the manufacturer's own and linked to the page they came from. Prices come from a live daily check; where we have no verified price we say so rather than print a stale one.
Ryobi 40V HP Whisper 17" Carbon Fiber RY402110
Ryobi · Ryobi 40V · Our score 8.6/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
67 published minutes and a swath you can dial from 15 to 17 inches -- the only adjustable-swath trimmer here.
Published specs
| Cutting swath | Adjustable 15-17 in |
|---|---|
| Line | 0.095 in bump feed |
| Shaft | Carbon fiber |
| Battery (kit) | 40V 6.0Ah |
| Runtime claim | Up to 67 min |
| Weight | 8.8 lb bare / 12.9 lb with 6.0Ah |
| Length | 72.25 in |
Source: 40V HP Brushless 17" String Trimmer (RY402110), ryobitools.com
40V x 6.0Ah = 240Wh. 67 minutes from 240Wh is about 3.6Wh per minute -- the most efficient published figure of the three trimmers here.
What the numbers favor
- 67 minutes published, more than double the EGO kit's 30
- Swath adjusts 15-17 in, so tight borders and open verge get the same tool
- Best published watt-hours per minute of the trimmers on this page
- Whisper Series noise engineering, same line as the 57 dB blower
What they don't
- 12.9 lb with the 6.0Ah pack fitted -- the heaviest trimmer here, and it is held at arm's length
- Ryobi publishes no noise figure for this specific model
- Bump feed, not an automatic reload head
you have wrist or shoulder trouble. 12.9 lb on the end of a 72 in shaft is a lot of leverage, whatever the runtime says.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Greenworks 80V 16" String Trimmer ST80L210
Greenworks · Greenworks 80V · Our score 8.4/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
7.1 lb bare with a 30-minute recharge and a 4-year battery warranty -- the lightest way onto the 80V platform.
Published specs
| Cutting swath | 16 in |
|---|---|
| Motor | Brushless, 6200 RPM |
| Line | 0.080 in spiral twist dual-line bump feed |
| Battery (kit) | 80V 2.0Ah |
| Runtime claim | Up to 45 min |
| Recharge | 30 min |
| Weight | 7.1 lb without battery |
| Warranty | 3-yr tool / 4-yr battery |
Source: 80V Cordless 16" Brushless String Trimmer (ST80L210), greenworkstools.com
80V x 2.0Ah = 160Wh. 45 minutes from 160Wh is about 3.6Wh per minute, matching the Ryobi almost exactly despite half the pack size.
What the numbers favor
- 7.1 lb bare, the lightest published trimmer weight here
- 30-minute recharge, the fastest on this page
- 4-year battery warranty
- Publishes motor RPM, which neither EGO nor Ryobi does for their trimmers
What they don't
- 0.080 in line is the lightest gauge here -- it will break more often in heavy weeds
- 160Wh included is a small pack for an 80V platform
- Bump feed, not automatic reload
you cut heavy brush or thick weed stems. 0.080 in line is a lawn-edge gauge, not a bramble gauge.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
EGO Power+ 15" POWERLOAD Carbon Fiber ST1521S
EGO · EGO 56V ARC Lithium · Our score 8.9/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
A lifetime shaft warranty and a head that reloads line at the push of a button -- the two things that actually go wrong with a string trimmer.
Published specs
| Cutting swath | 15 in |
|---|---|
| Line | 0.095 in dual-feed spiral twist |
| Head | POWERLOAD automatic winding |
| Shaft | Carbon fiber, split shaft |
| Battery (kit) | 56V 2.5Ah |
| Runtime claim | Up to 30 min on 2.5Ah |
| Charge time | 50 min |
| Warranty | 5-yr tool / 3-yr battery, lifetime shaft |
Source: POWER+ 15" POWERLOAD String Trimmer with Carbon Fiber Shaft, egopowerplus.com
56V x 2.5Ah = 140Wh. 30 minutes of published runtime from 140Wh is about 4.7Wh per minute -- roughly a quarter of what a blower on turbo burns.
What the numbers favor
- Lifetime warranty on the carbon fiber shaft, published
- POWERLOAD winds the line for you -- the job everyone hates
- 0.095 in line, the heavier of the two common home gauges
- Split shaft, so it takes EGO's multi-head attachments
What they don't
- Ships with the small 2.5Ah pack; 30 minutes is a modest published runtime
- EGO does not publish a weight for this configuration
you only edge a short driveway. An 8 in edger attachment on a power head you already own does that job better and costs a fraction.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Where to buy the tools on this page
Every link below is an Amazon affiliate link. We show no price we have not verified today, so where there is no live figure the link says "check price" and takes you to the listing to read it there.
Best runtime
Ryobi 40V HP Whisper 17" Carbon Fiber RY402110
Ryobi · Ryobi 40V
Best light 80V option
Greenworks 80V 16" String Trimmer ST80L210
Greenworks · Greenworks 80V
Best overall
EGO Power+ 15" POWERLOAD Carbon Fiber ST1521S
EGO · EGO 56V ARC Lithium
#ad As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. How we're funded.
Common questions
Is a higher voltage string trimmer better?
What voltage string trimmer do I need?
What do watt-hours mean on a trimmer battery?
Does voltage affect cutting power?
Is 40V enough for a string trimmer?
Sources
Read next
- Trimmers & Edgers
The line gauge and the head design decide whether you enjoy this job or dread it.
- 40V vs 80V: what the voltage on the sticker actually buys you
Volts x amp-hours = watt-hours. The one calculation that makes every battery spec comparable.
- Watt-hours explained: the one number that compares any two battery tools
Volts x amp-hours = watt-hours. Every pack in the registry converted, and why max volts overstates it.
- String trimmer buying guide: the four specs that matter
Line gauge, head type, shaft and loaded weight -- the four specs that decide how a trimmer feels.
- Best string trimmer for a large yard
Published runtime, watt-hours and energy per minute for four cordless trimmers on a big property.
- 40V vs 80V, tool by tool
Matched 40V and 80V pairs across mowers, blowers and trimmers, on published watt-hours and output.