20V vs 40V Cordless Trimmer: Which Voltage Fits Your Yard?
For a small yard with light trimming and edging, a 20V trimmer is usually enough, and it tends to be lighter. For larger lots, thick weeds or long sessions, a 40V or higher system gives you more stored energy and often a wider cut. Voltage is only part of the story, so compare battery energy in Wh, weight and cutting swath too.
EGO Power+ ST1502SABest overall
HortiHub HG0556-AORTwo batteries, light build
ALSO GO Weed trimmerLightest listed weightThe short version: match voltage to the job
A 20V trimmer suits quick tidy-ups along a fence, a driveway or a flower bed. A 40V trimmer suits bigger properties, tougher growth and longer stretches of work. Neither is better in every case.
The right pick depends on how much ground you cover and how long you want to work before stopping. It also depends on how much weight you are happy to hold. We cover each of those below, and our best cordless string trimmer page puts the listed specs side by side.
What voltage actually tells you
Voltage describes the electrical pressure of the battery system. On its own it does not tell you how long a trimmer will run. The number that matters more for runtime is battery energy, measured in watt-hours (Wh).
You can estimate Wh by multiplying volts by amp-hours (Ah). A 20V pack rated at 2.0Ah holds about 40 Wh. A 24V pack at 4.0Ah holds about 96 Wh. A 56V pack at 2.5Ah holds about 140 Wh.
That is why a higher voltage often, but not always, means more stored energy. A 20V pack with a big Ah rating can hold more than a small pack at a higher voltage. Always check the Wh figure when the maker lists it.
What the listed specs show
Among the trimmers on our comparison page, the 20V models with listed energy, such as the goodjob, the BLACK+DECKER and the WORX, each show 40 Wh. The 24V ALSO GO lists 96 Wh, and the 56V EGO POWER+ ST1502SA lists 140 Wh. The EGO has the highest voltage and battery energy of all 15 products.
The 40V class sits between those. Our page includes a 40V unit with a PowerCommand dial for choosing power or runtime. It is also the heaviest listed model, at 7.8 lb. Many 20V models are far lighter. The goodjob weighs 3.5 lb, and the HortiHub 21V weighs 5.27 lb.
The table below compares a few listed models. A dash means the maker did not list that spec on our page.
| Model | Voltage | Battery energy | Swath | Weight |
|---|---|---|---|---|
| goodjob 3-in-1 | 20V | 40 Wh | 12 in | 3.5 lb |
| BLACK+DECKER LST300 | 20V | 40 Wh | 12 in | 5.7 lb |
| HortiHub HG0556-AOR | 21V | - | 12 in | 5.27 lb |
| ALSO GO 24V | 24V | 96 Wh | - | 3.28 lb |
| EGO POWER+ ST1502SA | 56V | 140 Wh | 15 in | 7.4 lb |
When 20V is the better choice
Pick a 20V trimmer when your yard is small or medium and you mostly cut grass and light weeds. The lighter weight is a real benefit on long edging jobs, since your arms tire less.
Lower-voltage models also tend to use thinner line. The goodjob lists 0.065 in line, which works for regular grass and common weeds. If you already own batteries from a 20V tool line, a bare-tool option can also save you from buying another battery system. The DeWalt-compatible model on our page is one example, though it ships without a battery or charger.
- Small to medium lawns and garden beds
- Quick edging along walks and fences
- Users who want the lightest tool
- Homes that already own matching 20V batteries
When 40V or higher makes sense
Choose a higher-voltage system when you have a large lot, thick weeds or long sessions of work. More stored energy generally means more time between charges. A wider cut also helps, since fewer passes cover the same area. The EGO lists a 15 in swath, the widest on our page, and 0.095 in line for heavier growth.
The trade-off is weight. The 7.4 lb EGO and the 7.8 lb 40V model are heavier than most 20V options. If you are not sure you can hold that for a long job, a lighter tool plus a spare battery may suit you better.
How to decide in four steps
Use this quick process before you buy.
- Estimate your work time. If a normal session runs long, look for higher Wh or a second battery.
- Check the weed type. Thick or woody growth calls for a wider swath and thicker line.
- Set a weight limit. Lift the tool in your mind for the full job and be honest about fatigue.
- Confirm what is in the box. Some models leave out the battery or charger.
Safety notes
Wear safety glasses or goggles every time you trim. Stones and debris can fly out at high speed. Wear long pants and closed-toe shoes as well.
Cordless trimmers are quieter than gas models, but hearing protection is still wise during long sessions. Remove the battery before you change line, clear a jam or swap the head. Keep the guard on, and do not use a damaged battery or charger. Charge batteries indoors, away from flammable items.
Frequently asked questions
Can I put a 20V battery on a 40V trimmer?
Usually not. Battery packs are made for a specific brand and system. Check the maker's compatibility list before you try to mix them.
Does a higher voltage always mean a longer runtime?
No. Runtime depends on stored energy in Wh, the motor load and the thickness of the weeds. A 20V pack with a large Ah rating can hold more energy than a small higher-voltage pack.
Is a second battery better than moving up in voltage?
For many people, yes. A spare pack doubles your working time without adding weight to the tool. A higher-voltage tool mainly helps with tougher cutting and a wider swath.
Do runtime claims match real use?
Treat them as a guide. Only three of the 15 products on our page list runtime, and makers often give ranges that vary with load. Compare Wh for the rest.