A third man was arrested in connection with a rebate scam that defrauded National Grid, costing the company more than $1 million, Suffolk County police said.

Police arrested the owner of Star General Contracting, Michael Castronovo, of Franklin Square, nearly two months after two men were charged with identity theft and grand larceny for stealing the identity of local businesses to apply for rebate checks as part of National Grids Energy Efficiency Program.

Castronovo’s company name was used on the rebate applications as having completed the efficiency upgrades, police said. The efficiency upgrades were never performed, however, and the applications were submitted without the knowledge of the business owners who never asked that any work be done, police said.

National Grid offered the programs for commercial properties to perform upgrades that would conserve energy.

Last month, police arrested Ralph Bianco, of Farmingdale, and John Glaser, of Lindenhurst, for allegedly using identification of eight businesses in Suffolk County on National Grid rebate applications for rebates.

Information from businesses in Nassau and Suffolk counties netted the three men more than $1 million from National Grid, police said. Castronovo allegedly stole $78,680 from his activities in Suffolk.

Police became aware of the fraud four months ago when an Amityville business owner became suspicious after learning that someone applied for a rebate using his company’s information. A rebate was never issued, however, because the tax identification number for the business was not included on the application, police said.

Castronovo was charged with nine counts of identity theft and one count of grand larceny, police said. He was scheduled to be arraigned Friday at First District Court in Central Islip.

The investigation is continuing, police said, and more arrests are expected.