Greenworks AiMowbot C20, C30Z or C40?

Start with the lawn and the whole route

The separately reviewed C20 / RMG200R00 is listed for 0.5 acre and has an 8-inch cutting width. The C30Z / C30ZA1 is listed for 0.75 acre, also with an 8-inch path. The C40 / RMC04VR00 moves to a 12-inch path and a one-acre rating in its linked manual. These are recurring-maintenance robots, not wide-deck machines; a larger yard means more small passes, not a fast conventional cut. Makers' capacity values are conditional. The manuals describe tests with a full battery, standard speed and fresh-cut lawn at 25°C, and warn that wet or long grass, separated lawns and less-flat areas reduce capacity.

There is one exact-source caution for C40: its page title and prominent area field, plus its linked manual, say one acre, while a lower Product Specifications field says 0.5 acre. The evidence supports treating it as a one-acre maker claim, but leave practical margin instead of planning to the edge of that figure. Compare the C20 review, C30Z review and C40 review for exact model and manual distinctions.

The map, antenna and dock must fit too

Wire-free does not mean boundary-free. These systems use app-drawn virtual zones with an RTK reference antenna and charging station. You map the edges, make no-go areas, schedule the cuts and give the machine usable paths between lawn sections. A separate yard divided by a driveway may need a mapped link; a narrow gate or step can make the route impossible even if the grass area fits the model's claim. Before buying, find a position for the antenna with clear sky, power the dock in an open area and measure the tightest transit path. If trees or roofs prevent the antenna's required view, the installation may be a poor fit regardless of model size.

Cutting path is not the only hardware difference

The C20 and C30Z use an 8-inch cutting path and their respective manuals specify three blades. The C40 manual lists a five-blade cutting disc and 30 cm (11.8 inches) of width, rounded to 12 inches on the U.S. product page. All remain small compared with a walk-behind deck and are intended to make repeated maintenance passes. None of these exact product records confirms a conventional grass bag or side-discharge setup. If collecting clippings is essential, choose a configuration with a verified collection plan rather than assuming a robot can be adapted.

Check limitations before you choose the largest robot

All three require a safe mapped work area, periodic cleaning and blade inspection. The maker's maximum slope rating does not mean a steep, wet bank is safe to mow; confirm the manual's working-area guidance and consider actual traction, edges and transitions. Cameras and obstacle sensing do not replace removing toys, wire, sticks or stones, and users must keep children and pets clear. App and cellular connectivity also create an ownership dependency: check current service terms and local connection conditions rather than assuming remote features will remain included forever.

Choose C20 when its smaller rated area is enough and the narrower path fits your maintenance expectations. Step to C30Z only if its three-quarter-acre claim and exact configuration suit the mapped lawn. C40 is the larger-capacity option on the evidence above, with a wider robotic path, but it still needs suitable antenna sightlines, a dock, route mapping, regular upkeep and spare capacity. If those setup demands or the narrow cutting disc do not suit your property, a conventional push, self-propelled or riding mower is a better operating format.