How many volts for an electric lawn mower?

"How many volts?" is the most common question asked about cordless mowers and the least useful. Voltage is printed largest on the box because it sounds like power. What you actually want to know is how long the mower runs, and that is a different number entirely.

The short answer

The one calculation that matters

That is the entire point of this page. The 80V machine is not weaker — higher voltage genuinely helps a motor deliver power without drawing more current — but it ships with a smaller tank. Given the choice, buy the watt-hours.

What voltage does do

Voltage is not meaningless; it is just answering a different question.

• Voltage sets how hard the motor can pull at once. Power is volts times amps, so a higher-voltage system can deliver the same power at lower current, which means less heat in the wiring and more torque headroom in thick grass.
• Amp-hours set how long it can keep pulling. This is the fuel tank.
• Watt-hours are the two multiplied, and they are the only figure that compares packs across brands and voltages.

Four mowers, four voltages, one useful column

Read the last two columns together and the pattern holds: the 420Wh machine claims the longest runtime and the 160Wh machine the shortest, regardless of which has the biggest number on the box.

How many watt-hours your lawn needs

Published acreage ratings give a usable rule. Greenworks rates a 320Wh mower to half an acre and Kobalt rates a 640Wh machine to a full acre — both imply about 640 watt-hours per acre for a 21 inch walk-behind.

Those are floors, not targets. Every runtime claim on every product page is measured in conditions no manufacturer states, so buying the pack that exactly matches your arithmetic is how you end up recharging mid-mow.

Three mowers that illustrate it

The EGO LM2135SP carries the most energy here at 420Wh, with a published 60 minutes and the finest cut-height adjustment in our registry.

#ad Check the EGO Power+ 21" Select Cut LM2135SP price on Amazon — how we're funded.

The Greenworks LM2108S is the 80V machine: 320Wh, rated by its maker to half an acre, with a 4-in-1 deck and a four-year warranty on tool and battery.

#ad Check the Greenworks 80V 21" 4-in-1 LM2108S price on Amazon — how we're funded.

The Greenworks LM2054 is the 40V one: 160Wh, 57.5 lb, rated to a third of an acre, and the lightest mower we hold a published weight for.

#ad Check the Greenworks 40V 20" Push LM2054 price on Amazon — how we're funded.

Four rules for shopping on voltage

1. Convert every pack to watt-hours before comparing. Volts times amp-hours, every time.
2. Note whether a voltage is nominal or max. A 20% difference in the advertised figure can be a labeling convention, not a capability.
3. Check what the runtime claim assumes. Usually nothing stated — which is why the watt-hour figure is more trustworthy than the minutes.
4. Pick the platform before the voltage. Packs are not interchangeable across brands at any voltage — see battery compatibility.

What we cannot tell you

We have not measured runtime on any of these mowers. Every watt-hour figure above except Toro's is nameplate arithmetic on advertised voltage, and brands do not all advertise voltage the same way. No manufacturer publishes the grass height, density or moisture behind its runtime claim, and none publishes how capacity fades over the life of a pack — which is the figure that decides what your mower does in year five.