A recent experiment conducted by The Perfect Little Company (TPLC) concluded that by using commercial robotic vacuums in offices, over 11 thousand tons of greenhouse gases could be saved each year.
Using a certified power metre reader, TPLC pitted one famous commercial mid-sized tub vacuum up against one Hive (10 robots) and monitored the electricity needed to operate both. The tub vacuum working for two hours had an electricity consumption cost of 1.44kWh. To fully charge one Hive containing 10 robots took 0.54kWh of electric and they were capable of covering the same area - about 7000 sq ft.
In London alone (which has over 200 million square ft of office space) this would equate to reducing the carbon output of vacuuming by a massive 2700 tons per year. Additionally, this would save on the costs of vacuum bags, landfill and electricity.