Kenya's coast gateway substation moves to 400kV, and coastal diesel running falls to 35MW.

For a large power user on Kenya's coast, the electricity behind the meter now arrives mostly down a high voltage corridor from upcountry rather than from expensive plant burning fuel nearby. The transmission company's Mariakani substation in Kilifi County, built originally as a 220kV facility, was commissioned fully energised at 400/220kV in May 2026.

The substation and its associated lines were in commercial operation before the ceremony, energised in December 2025, and thermal generation on the coast has since fallen from 100MW to 35MW, a cut of 65 per cent. Mariakani sits on the transmission route between Nairobi and Mombasa, built to move more than 1,000MW between the two, and the upgrade lets the coast draw more heavily on the Olkaria and Suswa switching points inland. The transmission company reports that the 400kV double circuit line running from Mariakani to Isinya has steadied voltage and improved power quality across the region.

The build cost KES 4 billion, funded by the Kenyan government together with the African Development Bank. The same company frames the reinforcement as the condition for getting full use out of the 500kV high voltage direct current link to Ethiopia and the 400kV link to Tanzania, both of which feed a national grid that has to be strong enough to move what they deliver.

On this reading, the security question for a coastal industrial site has changed shape rather than gone away: less exposure to the cost of fuel burned down the road, more dependence on one long corridor and on the substation at the end of it holding up through evening and dry season peaks.

For large power users, a cheaper import route is worth little if the path carrying it is unavailable when demand is highest, so it is worth asking your supplier what firm supply looks like at the evening peak with the high voltage corridor out. Check whether your supply agreement still prices standby diesel you now expect to run far less, and which curtailment terms bite when voltage support on the coastal network is tight.