Electricity officials said high winds and bad weather had cut a high voltage power line, pitching the eastern half of the country into darkness. The capital, Tbilisi, was also without electricity after a unit at a power station collapsed under the strain of having to work at full capacity.
Georgia has been struggling to cope with limited supplies of natural gas after two explosions on Sunday hit a pipeline in Russia carrying supplies to Georgia. Since then, many people have been heating their homes with wood stoves or camping gas.
The energy crisis has brought a new chill to already frosty relations between ex-Soviet Georgia and neighbouring Russia.
President Mikhail Saakashvili has accused Russia of deliberately blowing up the gas pipeline to apply political pressure on Tbilisi's pro-Western leadership. Moscow fiercely denied the claim, accusing Tbilisi of hysteria.
Saakashvili on Thursday cut short his trip to the World Economic Forum in Davos, Switzerland, to return home to help Georgia through the crisis.
The temperature in Tbilisi was minus 5 Celsius (minus 23 Fahrenheit), bitterly cold for a country known for its palm tree-lined Black Sea coast.
"There was an accident on one of the high voltage electricity lines," said Valery Panculaia, a spokesman for Tbilisi's electricity distribution company, Telasi, told Reuters. "We hope we will solve this problem by tomorrow evening."
Georgia's electricity problems began at the weekend when a line used to transmit extra power from Russia's grid was blown up one hour before the gas pipeline explosion. The blast was on the Russian section of the line.
Russia's electricity supplier said it was transmitting extra power to Georgia via other routes to help cover the deficit. Talks have opened with Azerbaijan and Armenia to get additional electricity supplies.
After gas supplies to Georgia were cut, Russia promised to fix the pipeline in days and, as a stop-gap, deliver extra gas to Georgia via another route through neighbouring Azerbaijan.
But Georgia's Prime Minister Zurab Nogaideli said the extra gas had not materialised. Azerbaijan was instead giving Georgia some of the gas it would normally supply to its own consumers.