Lightning caused around 600 households to be left without power on Monday morning.
Scottish and Southern Electricity Networks (SSEN) apologised for the disruption, which was caused when lightning hit a transformer at 8.08am.
People in Scalloway complained about a loss of power early on Monday morning, and SSEN said that the outage had affected around 600 households.
Engineers worked to restore the fault through the morning, and restored power in stages.
Power was restored to all customers by 12.45pm, SSEN said on Monday afternoon.
“We would like to apologise to our customers for any inconvenience caused by this morning’s power cut and thank them for their patience, while our engineers worked as safely and as quickly as possible to repair the damage caused to the network by the lighting strike,” a spokesperson for the company said.