Kenya Power reported a blackout occurred at 0745 GMT, after towers supporting a high voltage power line connecting the capital to the Kiambere hydroelectric dam collapsed.
A company spokesperson confirmed the outage was nationwide.
It said in a statement that as of 1435 GMT, power had been restored in all parts of the country except in three administrative regions, know as counties, and whose supply was expected back by 1500 GMT.
"Work has also commenced to reconstruct the collapsed electricity towers," Kenya Power said.
Kenya Power is the country's sole electricity distributor and the bulk of its power comes from Kenya Electricity Generating Company (KenGen).
In May 2020, Kenya experienced a similar nationwide outage after a section of a high voltage power line that transmits power to Nairobi from the Olkaria geothermal power plants, some 75 km (45 miles) from Nairobi, broke.
In late December, a section of another transmission line known as Loyaingalani-Suswa, collapsed, knocking out some power supply and leading to power rationing in parts of the country while it was being repaired.
(Reporting by George Obulutsa; editing by Jason Neely and Tomasz Janowski)
By George Obulutsa
