The state electricity provider is also reported to be unable to pay its debts to suppliers and transport companies.
Coal-fired stations in the capital, Harare, and in the second city, Bulawayo, have already been shut down.
Zimbabwe's main external power provider South Africa says it has temporarily halted supplies for maintenance work.
"I would like to bring to the attention of all consumers that the current load shedding due to supply shortfall is set to worsen," head of the power regulatory commission, Mavis Chidzonga, was quoted in Zimbabwe's Sunday Mail as saying.
She warned that electricity production at the Hwange facility servicing north-west Zimbabwe may also have to be reduced due to the shortages.
She said the recent coal shortages had been made worse by the state electricity provider's inability to pay its debts to suppliers and transporters....