40V vs 20V Trimmer: How Much Power Do You Need? (October 2026)

On this page (9 sections)

1. 40V vs 20V trimmer: which should you choose?
2. What does voltage tell you about a trimmer?
3. Which trimmer is easier to carry and control?
4. Which voltage suits routine lawn trimming?
5. Which model makes more sense for thicker weeds?
6. How do line feed and edging change the choice?
7. What should you check before buying a 20V or 40V trimmer?
8. Verdict: 40V vs 20V trimmer
9. Sources

Choose a 20V trimmer for light trimming and easier handling; look at 40V models when you want more power options or a wider cutting path. A higher voltage rating can be useful, but the right 40V vs 20V trimmer depends on the grass, weeds and features you need.

The WORX WG163 is the lightest option here at 5.5 lb, and it converts from trimmer to edger. The Greenworks 40V has variable speed control, while the BLACK+DECKER 40V MAX offers a 13 in cutting width and a dial for choosing maximum power or runtime.

Voltage doesn't promise a particular runtime or cut quality by itself. Compare the tool's weight, line system and controls with the work you expect to do.

40V vs 20V trimmer: which should you choose?

Choose 20V for lighter routine work and easy handling; choose a 40V model when its controls or wider path fit your yard better. The voltage label is one part of the decision, not a full measure of performance.

The WORX WG163 weighs 5.5 lb and includes two 20V batteries. Its head tilts 90 degrees, and its rubberized wheels support edging.

The Greenworks 40V weighs 12 lb and uses a 12 in dual-line cutting path. Its variable-speed trigger lets you adjust power for the task.

The BLACK+DECKER 40V MAX weighs 7.8 lb, cuts a 13 in path and has a PowerCommand dial with maximum power and maximum runtime settings. Those differences can matter more than voltage when you compare these specific tools.

For broader factors such as shaft design, power source and weight, see the string trimmer buying guide. If you already know you want a cordless model, the best cordless weed eaters for home lawns page offers more options.

What does voltage tell you about a trimmer?

Voltage identifies the battery system's electrical rating, but it doesn't tell you runtime or cutting ability on its own. Treat it as a useful comparison point, then check the tool features and task.

A trimmer's cutting work also depends on its line, motor and design. Line diameter, cutting width, feed system and speed controls can affect how it handles grass and weeds.

The products here show why a single number isn't enough. The WORX 20V WG163 lists a 12 in cutting diameter and 7600 RPM no-load speed, while the BLACK+DECKER 40V MAX lists up to 8500 RPM and a 13 in cutting width.

Those figures describe different aspects of the tools. They don't tell you which one will cut faster in your yard or how long its battery will last.

Does 40V mean twice the power of 20V?

No, the voltage label alone doesn't mean a trimmer will deliver twice the cutting power. Actual output depends on the tool's electrical and mechanical design, along with the work being done.

Grass height, weed thickness, line condition and the way you move the tool all affect the load. A higher voltage rating can't guarantee a clean cut through heavy growth if the trimmer's other features aren't suited to that job.

Compare the maker's runtime guidance and tool features for your intended use. If you regularly tackle dense growth, also see our guide to weed wackers for heavy brush.

Which trimmer is easier to carry and control?

The WORX WG163 is the lightest of these 3 at 5.5 lb, while the Greenworks is the heaviest at 12 lb. Weight can shape how comfortable a trimmer feels over a long session, especially when reaching around fences or beds.

The BLACK+DECKER is listed at 7.8 lb. Compare that figure with the complete tool's balance and handle position when choosing, since listed weight alone doesn't show how it feels in use.

WORX adds rubberized wheels for edging and a 90-degree tilting head for sloped areas. These features can help guide the tool along a border, but they don't make it a fit for every yard.

If weight is a priority, our guide to string trimmer weight explains what to check and how to think about handling.

How much does trimming posture matter?

A lighter tool may be easier to guide, but shaft length, grip and balance still matter. Try to keep the cutting head near the ground without bending or twisting your back.

The BLACK+DECKER has an adjustable telescoping pole and soft-grip handle. The WORX includes a tilting head and an adjustable spacer guard, which can help with edging and protecting plants.

Use eye protection and follow the safety instructions for your exact tool. Keep people and pets away from the cutting area while the line is moving.

Which voltage suits routine lawn trimming?

For short sessions on grass and light weeds, pick the trimmer with a manageable weight, a useful line system and controls that match your routine. A small lawn doesn't automatically require a lower voltage, and a 40V tool may still suit light work.

The Greenworks 40V uses 0.065 in dual line and has an auto feed system. Its trigger gives you variable speed, so you can adjust power for edging or extra power when needed.

The WORX 20V WG163 uses 0.065 in line and a push-button command feed spool. It converts to an edger, with support wheels for guiding the edge.

For either model, think about how often you edge and whether you prefer automatic or button-controlled line feed. The guide to trimmer line size can help you understand how line choices relate to the work.

Which model makes more sense for thicker weeds?

The BLACK+DECKER 40V MAX is the clearest fit here for thicker weeds because it has a maximum-power setting and a 13 in cutting width. That doesn't guarantee it will handle every overgrown patch, so use the tool within its instructions.

The Greenworks 40V also offers variable speed and describes extra power for thicker grass. Its 12 in cutting path and 0.065 in dual line are aimed at grass and light weeds around lawns and landscaping.

The WORX 20V model is designed for trimming and edging, and its stated specs don't describe a heavy-growth use. For thick weeds or brush, consider a tool made for that workload rather than expecting voltage alone to compensate.

How do line feed and edging change the choice?

Choose a feed system you can use comfortably and an edging setup that fits the borders in your yard. These details affect the job each time you trim, regardless of the voltage label.

The Greenworks and BLACK+DECKER use automatic feed systems. WORX uses a push-button command feed spool that advances line when you press the control.

For edging, the WORX converts to an edger, has rubberized wheels and a tilting head. The BLACK+DECKER also converts to an edger, while the Greenworks is described for edging and trimming with variable-speed control.

Check your preferred method before you buy. If your main problem is frequent line breakage, read why trimmer string keeps breaking for common causes and practical fixes.

What should you check before buying a 20V or 40V trimmer?

Check battery compatibility, included batteries, weight, line system and the maker's runtime guidance for the exact model. These details can prevent a mismatch between the tool and your yard.

WORX says its Power Share batteries are compatible with its 20V and 40V tools. That is a brand-specific compatibility statement, not a general rule for other trimmer brands.

The WORX WG163 comes with two batteries, while each 40V model here includes a battery and charger. Confirm the included kit and any compatibility details before ordering, since product families can vary.

Look at charging time and battery capacity if you trim for long stretches. Our guide to weed eater battery charging time explains what can affect a recharge.

Verdict: 40V vs 20V trimmer

Pick the WORX 20V WG163 for lighter handling and edging, the Greenworks 40V for variable speed on routine lawn work, or the BLACK+DECKER 40V MAX for a wider path and a maximum-power setting. Match the choice to your yard's growth, your preferred line feed and the tool weight you can manage.

For mostly light grass and borders, the WORX's 5.5 lb weight and edger features stand out. If you need more control over power, compare the two 40V options by their weight and cutting width.

See the best 20V string trimmers or best 40V string trimmers for more options in each voltage group. For a wider view of battery versus gas tools, read string trimmer gas vs battery.

Sources

• WORX WG163 product information
• BLACK+DECKER LST136 product information
• Greenworks 40V trimmer product information

Frequently asked questions

Is a 40V trimmer more powerful than a 20V trimmer?

A 40V trimmer has a higher voltage rating, but voltage alone doesn't tell you how well it will cut or how long it will run. Line size, motor design, cutting width and the task all matter.

Compare features for the kind of grass and weeds in your yard.

What is the difference between a 20V and 40V trimmer?

The main stated difference is the battery system voltage, but the tools can also vary in weight, line feed, cutting width and controls. For example, the WORX WG163 is a 5.5 lb 20V trimmer and edger, while the 40V models here weigh more or have a wider cutting path.

Is a 20V trimmer enough for a small yard?

A 20V trimmer can be enough for routine edging and light grass in a small yard, especially if easy handling matters. The WORX WG163 weighs 5.5 lb and converts to an edger.

For thick weeds or overgrown areas, compare a higher-voltage model and its cutting features.

Does a 40V trimmer last longer than a 20V trimmer?

Voltage by itself doesn't guarantee runtime. Battery capacity, speed setting, line, vegetation and how often you stop all affect how long a trimmer runs.

Check the battery capacity and runtime information for the exact model, and consider a spare battery if you have a larger area.

Can you use a 40V battery in a 20V trimmer?

Only use a battery that the tool maker identifies as compatible with that exact trimmer. Voltage and battery shape can vary across product families, and a battery that physically fits may still be unsuitable.

Check the tool manual and the maker's compatibility chart before connecting a different battery.