PUREi9, $1699
Relying on visual sensors and memory to get around, this appliance can be inefficient, at least initially as it builds up a map, or if objects are moved around the home – not ideal with only 40 minutes per charge. The upside of its cautious algorithm is the PUREi9 approaches objects gently. The roller's combination of rubber and bristles handles different dirt and surfaces well, and the wide side brush gets into corners particularly effectively.

ROOMBA 980, $1499
Generally working in straight lines, and with sensors on the home base to help it dock, this makes efficient use of its two-hour charge. It tends to bump into things, so two small, included accessories that can be placed anywhere to create virtual walls are useful for protecting fragile objects (or block off rooms). It's slightly noisier, the filter needs replacing every two months (compared to the PUREi9's six) and the dirt container is smaller.

VERDICT: If you aren't around to watch your robot vacuum in action, the end result suggests there's little to separate these two appliances. The PUREi9 seems to obsess over where it is and what's in its way, especially during initial mapping, whereas the Roomba is fast and efficient from the get-go.

CHECK THIS OUT: Recent additions to the high-tech cleaning brigade include robot mops, such as the iRobot Braava, and window cleaners. If you dislike climbing ladders encumbered with window-cleaning gear, the Winbot, Hobot or RobotZoo's Gecko or Glider may be your salvation. They scoot around automatically or by remote control, in most cases sticking to windows by motorised suction and cleaning with microfibre pads.