The Capital and Coast District Health Board says the recent failure of Wellington hospital's electricity supply never put any patients at risk.
Board papers show the Uninterruptable Power Supply that powers the hospital's data centre was disrupted on 1 June.
The DHB says this was a one-off event which only lasted a couple of hours and did not affect the hospital or surrounding buildings.
It says the data centre's outage was a result of nearby construction work.
The outage follows an incident in April in which the hospital's back-up generators failed to come on immediately when the power went off.