* Supplies already stretched after 2011 disaster
* Power unit stopped functioning overnight (Adds details)
NICOSIA, April 4 Power started to return to Cyprus on Wednesday after a major outage left 80 percent of the island without electricity, highlighting an energy shortage caused by a blast that crippled its main generating facility in 2011.
Authorities said a unit at Dhekelia power station stopped functioning overnight, triggering breakdowns throughout the system. By mid-morning, power was gradually starting to return to most areas.
"We have restored supply," a spokesman for the state-controlled Cyprus Electricity Authority said.
"The generating capacity was there, but there was a problem of getting it onto the grid," he said.
Cyprus's electricity resources are already stretched after its main power generating facility at Vassilikos was almost totally destroyed in an accidental explosion in 2011.
The disaster forced authorities to put ageing stations back online and to get supplies from a breakaway Turkish Cypriot state, which lies north of a ceasefire line dividing the war-divided island.
The island's transmissions systems operator reported power generation fell by more than half overnight to 123 megawatts (MW) of electricity, but supplies on the grid started building up by mid-morning as more sources came online.
It was unclear what caused the fault at Dhekelia, which operates on six 60-MW steam units and two 50-MW internal combustion units. It also has capacity from the Moni power station with six 30-MW steam units and four 38-MW steam units.
Cyprus lost more than 700 MW of its production capacity when Vassilikos, which supplied more than 50 percent of the island's needs, was destroyed.
Some 165 MW in mobile generator production capacity will be supplemented by another 120 MW to cope with increased demand over Cyprus's hot summer months. (Reporting By Michele Kambas; Editing by Erica Billingham and Alison Birrane)