Kenya Power said on Monday a technical fault at one of its substations in the north of the capital has caused an electricity outage that was affecting Nairobi, Mount Kenya and Coast regions.
Kenya Power said its technicians were working to restore the supply as soon as possible.
"A technical fault occurred at a Kenya Power substation in Ndenderu (Nairobi North Substation) this morning cutting off supplies from Olkaria geothermal fields to the City and causing a power outage ..." it said in a statement.
Industrial consumers in Nairobi and the neighbouring town of Thika, both affected by the outage, generate 60 percent of Kenya Power's revenues.
Many firms in Kenya run stand-by generators to address frequent power interruptions, adding to their costs. Businesses say unreliable power supplies are a major obstacle to investment.