"Today we ran the plant fully on coal," power minister Patali Ranawaka told reporters Friday.
On Friday night the plant had also been successfully connected to the grid at full load for the first time, officials said.
The plant can generate up to 315 MegaWatts of power but can export between 285MW to 300MW the grid after using part of the energy for its own operations such as running a coal crushing plant and its cooling systems.
Ranawaka said coal prices were also rising and at current prices the cost of generating a unit of power from coal was 6.40 rupees.
But diesel prices are also rising and the cost of liquid thermal generation was also rising.Minister Ranawaka said coal spot prices were spiking faster than normal as many countries had built new coal plants in recent years.
Coal is mostly sold on long term contracts and utilities in many countries usually manage cost rises better than liquid fuels.