The power breakdown occurred around 10 PM yesterday and the situation worsened as Karachi Electric the main power supplier to said the main transmission and distribution lines had developed a fault resulting in closure of grid stations.
The city of around 20 million last month also faced unusual power breakdowns with a heatwave claiming over 1,300 lives.
Many parts of Karachi remained without power throughout the night and even until this afternoon power had been not been restored to half the city.
Last week also a similar power breakdown had lasted for around 16 hours in Karachi.