36V vs 40V cordless brush cutter: does the voltage matter?

Two cordless brush cutters sitting side by side, one labelled 36V and the other 40V, look like a straightforward “more power wins” decision. It isn’t. Voltage is one input into motor output, and by itself it tells you almost nothing about how a machine will handle brambles, saplings or long grass.

Why the number is misleading

Battery voltage is measured two ways: nominal (the average voltage over a full discharge cycle) and maximum (the peak voltage straight off the charger). A pack built from ten 3.6V lithium-ion cells in series is nominally 36V but reads roughly 40V fully charged. Some brands market that exact pack as “36V”, others market the identical chemistry as “40V max”. Same cells, same energy, different sticker. This is why you’ll see “36V” and “40V” ranges from different manufacturers that are, in practice, interchangeable in performance.

What actually drives cutting power is the combination of voltage, battery amperage (current draw), the motor’s design, and how the controller manages that power under load. A brushless motor paired with a well-cooled controller on a 36V platform can comfortably out-torque a budget 40V machine with a weaker motor winding. Voltage alone is not a proxy for torque, RPM, or stall resistance.

What to check instead

• Watt-hours (Wh), not volts — this is the real energy figure. Multiply voltage by amp-hours to compare packs fairly across brands.
• No-load RPM and stated torque — where the spec sheet gives them, these tell you more about actual cutting ability than the battery voltage.
• Head type and cutting width — a 30–43 cm cutting swath with a metal blade needs more sustained torque than a thin nylon line head, regardless of voltage.
• Ecosystem — if you already own batteries for a mower, hedge trimmer or drill on one platform, matching voltage and brand saves real money over time.

At a glance

	36V platform	40V platform
Typical use case	Light-to-medium grass, tidy gardens	Light-to-medium grass, tidy gardens
Real-world cutting power	Depends on motor/controller — varies widely	Depends on motor/controller — varies widely
Runtime	Set by Ah, not voltage — check pack capacity	Set by Ah, not voltage — check pack capacity
Battery weight	Generally lighter packs in this class	Often slightly heavier packs, marginal difference
Ecosystem breadth	Wide across budget and mid-range brands	Wide across budget and mid-range brands
Cross-brand compatibility	None — proprietary per brand	None — proprietary per brand
Price positioning	Entry to mid-range	Entry to mid-range
Marketing clarity	Often nominal voltage (more honest)	Often max voltage (inflated by ~10%)

Neither column wins outright — that’s the point. The genuine differentiator is which battery ecosystem you’re already invested in, not the number on the box.

Choose 36V if…

• You already own 36V batteries and chargers for another tool from the same range and want to reuse them.
• You’ve compared actual amp-hour figures and found a 36V pack with better Wh-per-cost than the 40V alternative you’re considering.
• The listing gives you a nominal (honest) voltage rating alongside real torque or RPM figures you can trust.

Choose 40V if…

• Your existing garden tools (mower, hedge trimmer, chainsaw) are already on a 40V platform from the same brand — buy into the ecosystem you have.
• The 40V model in question publishes higher amp-hours or watt-hours for a similar price, giving you genuinely more energy per charge.
• You’re starting from scratch and the 40V range from your preferred brand has the widest selection of heads and attachments.

Which should you buy?

Ignore the badge and compare like for like: watt-hours, motor type (brushless is worth paying extra for), head compatibility, and — above all — whether you already own batteries on one of these platforms. If you’re brand-agnostic and starting fresh, a 40V-labelled pack is very slightly more likely to be marketed with max rather than nominal voltage, so treat any voltage claim as a rough guide and read the amp-hour and weight figures on the actual battery before comparing two machines. For a broader look at how cordless machines stack up against petrol, see our electric vs petrol brush cutter comparison; for battery platform lock-in generally, check the brand pages for the ranges you’re weighing up on /brands/.

The honest verdict: 36V vs 40V is not a meaningful fight. Buy on ecosystem fit and real power figures, not the number stamped on the casing.