The Manx Health Department has been criticised for failing to install a back-up power supply during the building of Noble's Hospital.
The hospital, which opened in 2003, was built with a single supply and has a generator in case power fails.
Health Minister David Anderson has now asked Tynwald for £700,000 towards the £1.4 million cost of a second supply.
East Douglas MHK member Brenda Cannell has described its original exclusion as "scandalous".
Tynwald has approved its funding, but Ms Cannell said: "There were quite a number of us who weren't happy with how it was taken forward at the time.
"The decision was taken that the [health department] couldn't afford it because of the extortionate cost of the hospital and they were advised that they could get away with one source of supply plus a generator for back-up."
She said that a number of MHKs agreed with her that the department should have realised the importance of a second supply at the time of the hospital's construction.