Atkinson left the new £289 million Peterborough City Hospital in a wheelchair having been admitted the previous evening.
A spokeswoman for the hospital, which was built under a Private Finance Initiative (PFI) scheme, said power went down in some parts of the building at 10.15pm on Thursday following a power failure in the north of the city.
A back-up generator failed to operate properly and an investigation is under way to find out why.
The emergency department was blacked out as was the critical care unit, the neo-natal intensive care unit, maternity, and some operating theatres, though no operations were taking place at that time of night.
Power was restored at 2.30am on Friday. Four operations due to take place on Friday morning were cancelled while safety checks took place.
The spokeswoman said: “A major incident was declared and the action plan was initiated. Ten additional staff members were brought into the hospital to help move patients and manage the situation.
“During this period the emergency department was relocated into the adjacent ward area and emergency calls were diverted to other hospitals. Patient safety remained a priority at all times and patient care was not compromised in any way.”
Rowena Barnes, chief operating officer, said: “I would like to thank our staff, the East of England Ambulance Trust, and our neighbouring hospitals for their help and support during the incident.”
Atkinson,. 56, who starred as Blackadder and Mr Bean, is believed to have suffered a shoulder injury after the accident on the A605 in Haddon, Cambridgeshire. He was driving his McLaren F1 supercar when it spun around several times, ran into a tree and a lamppost and caught fire, according to reports.