A thousand homes and businesses in Lerwick lost power on Monday afternoon along with a number of other properties in the West Side.
The blackout happened shortly after 4pm when a problem occurred with an underground power cable.
A spokeswoman for Scottish and Southern Energy said areas like Sandness and Weisdale had their power restored within 10 to 15 minutes, while in the town power went back on in stages. Half of those properties blacked out in Lerwick had their power back within 40 minutes.
She said engineers were busy rerouting the power through alternative feeds in the network before isolating the part at fault for repairs.
She added there had been a “suggestion” the cable had been “unsettled” some weeks ago when other work was going on nearby.
“We apologise to anybody who had their power interrupted yesterday whether it was for 10 minutes or longer,” the spokeswoman said.