AUGUSTA — The State House and a few other major state buildings are now heated by natural gas.

The state Bureau of General Services this week announced the State House, Cross State Office Building, Cultural Building and the Department of Health and Human Services headquarters at 221 State St., have fully made the conversation to natural gas.

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Other state buildings to be converted include the powerhouse at the state’s east side campus on the former grounds of Augusta Mental Health Institute, and the adjacent Riverview Psychiatric Center. Both are scheduled to be converted to gas in early March, completing phase one of a planned series of conversions at Augusta-area state buildings.

Last fall the state, following a bid process, awarded natural gas distribution deals for 30 state-owned properties in the Augusta area. Maine Natural Gas won the right to serve 19 sites, providing the bulk of the gas, while competitor Summit Natural Gas of Maine will provide gas to 11, mostly smaller, sites.

Sawin Millett Jr., commissioner of the Department of Administrative and Financial Services, said the switch to a new fuel will save taxpayers at least $708,000 this year alone.

Officials of Maine Natural Gas, a subsidiary of Iberdrola USA, which also owns Central Maine Power, said the Brunswick-based company will deliver about 90 percent of the natural gas used by the state in Augusta, including gas to the four buildings already connected.

The successful bid awards were the state’s second attempt. In 2011, after the state had selected Maine Natural Gas to supply gas to state facilities, the state’s selection process was deemed to be flawed, and all bids were rejected.