The firm Thursday evening said the hitch was solved, adding that a backlog of purchases prevented users from accessing their electricity tokens.
M-Pesa payments for the service were going through, but the token issuing system remained unresponsive.
“We experienced a technical challenge yesterday night (Wednesday), around 10.30pm, leading to unprecedented shutdown of our prepaid system,” Kenya Power said in a statement.
“Our IT team has been working round the clock to ensure speedy restoration of the system. Normalcy (is) expected later this evening (Thursday). We are clearing the backlog.”
Kenya Power processes up to 200,000 electronic top-up transactions per day, 85 per cent of it through the M-Pesa paybill number 888880.
The remaining transactions are handled by third-party vendors such as Dynamo (paybill number 800904) and VendIT (501200).
Customers who used Kenya Power’s M-Pesa paybill number 888880 to buy tokens, however, questioned why the company took so long to address the issue.