State power utility Zesco has applied to the Energy Regulation Board (ERB) to increase tariffs by more than 300% in some cases to help clear its debts and offset the higher cost of generation from new plants.Residential tariffs for consumption up to 100kWh would rise to 0.47 kwacha (about $0.04) from 0.15, while consumption of 101-300kWh would remain at 0.85 kwacha and consumption over 301kWh would rise to 1.94 kwacha from 0.89.