Jason Haines has written recently about The future of robot mowers today and I recommend having a read of that post for more insight, and some videos of these types of machines.
There was an article in the August 2018 issue of HortTechnology that surprised me. This article, by Pirchio et al., Autonomous rotary mower versus ordinary reel mower—effects of cutting height and nitrogen rate on Manila Grass [sic] turf quality, describes an experiment that had these results:
“Our prototype autonomous mower working at a 1.2-cm mowing height produced a higher quality turf and increased shoot density compared both with the reel mower and to the machines working at a 3.6-cm mowing height. The energy saving was also optimized by both autonomous mowers.
These encouraging results show that autonomous mowers have the potential to perform optimal turf maintenance not only of home lawns and large ornamental areas, but also of quality sports turfs, such as golf tees and golf roughs, even on tough-to-mow turfgrass species.”
Manilagrass is notoriously difficult to mow, so that result with the autonomous rotary mower surprised me. Also, there was a big difference in energy use and cost. The autonomous mower at 12 mm used 1.9 kWh/week; the reel mower energy consumption was 5.4 kWh/week. And the estimated costs were 11 euros/week for the autonomous mower and 30 euros/week for the reel mower.
The article by Pirchio et al. is really interesting and I suggest reading it to get all the details. For example, the reel mower at 12 mm had a cutting frequency of twice per week; the autonomous mower mowed daily, etc. That’s the part that probably contributes to turf quality and shoot density differences. Even with the daily mowing, though, the autonomous mower had a lower energy consumption and lower operation cost.