Hawaiian Electric Co. is looking to increase the amount of electricity it gets from coal.

In a filing submitted Jan. 22, HECO asked the Public Utilities Commission to approve an increase in its contract with AES Hawaii Inc., the only coal-fired plant on Oahu, to 189 megawatts from 180 megawatts.

HECO said the additional capacity supports the company’s vision for its future power plan by improving its generating system reliability in a cost-effective manner.

“This amendment will help lower customer bills while providing additional firm dispatchable capacity to Hawaiian Electric’s grid,” HECO said in the filing.

Coal releases more carbon dioxide than oil when burned to produce a given amount of electricity, but coal is generally considered cheaper than oil.

In the filing, HECO said the cost for power from AES was approximately 9.6 cents a kilowatt-hour. According to the PUC 2015 annual report, AES was the lowest-cost power producer in the state.

HECO said the additional 9 megawatts from AES will reduce the amount of the anticipated shortfall as the utility retires its oil-fired plants. HECO said its reserve capacity may not be sufficient as it continues with its plans to deactivate Waiau units 3 and 4 at the end of 2017. Waiau units 3 and 4 have a combined 92.6-megawatt capacity.