Newham University Hospital NHS Trust has cut costs by deploying software from energy management specialist 1E.
The trust said it expects to save around £18,500 a year with the new tools.
Shaun Jeffery, ICT operations manager at Newham University Hospital NHS Trust, said: "One month in and we were already saving approximately £1,250 per month across just the PCs which have had the agreed power policy applied. In just one year, we stand to reduce our carbon emissions by approximately 143 metric tonnes a year."
The NightWatchman tool was deployed across the trust's 1,500 computers and follows implementation of a software distribution platform, Microsoft System Centre Configuration Manager.