All laptop users are required to run on battery power throughout the day until 20% and then they plug in.
How is that green? As already pointed out, wear and tear will go up, consuming energy to manufacture and transport more batteries. Plus recharging the batteries will take *more* power to recharge them was discharged from them (due to efficiency lost in both the charging circuitry and the chemical processes involved. A quick google suggests at least a 10-15% hit).
Plus, most machines' default power profiles reduce performance when running on battery, so I wouldn't be surprised if things take longer to accomplish. i.e. Less work out of people, for the same overhead costs and environmental power usage (heat, lights, etc). [side note to pedants: any power savings from cpu throttling/spindown could be gained independent of battery usage by managing power settings, so it could still be accomplished where actually desired]
Unless running on battery is able to shift the consumption from daytime to seriously off-peak (past 7pm?), it's probably consuming more power....especially if everyone runs low and plugs in at the same time, or plugs in just before heading home and adds to the residential peak typical at quitting time.
Sounds like another bright PHB idea, like reducing heating in winter will save the company money......until they start to wonder why everyone types slower in gloves and makes more typos...