The state has awarded a $17.4 million contract to a mainland company to undertake energy efficiency improvements and install solar panels at 33 government buildings on five islands.

The project is expected to cut energy costs by more than $1 million in the first year and $28 million over two decades, according to Ameresco Inc., the Massachusetts-based company that was awarded the contract by the Department of Accounting and General Services.

The contract includes the installation of solar photovoltaic panels at 13 facilities that will produce an estimated 1.3 million kilowatt-hours of electricity a year. That is roughly the energy use of 180 households using 600 kilowatt-hours of electricity a month.

Ameresco will install 3,370 PV panels on buildings on Oahu, Kauai, Maui, Molo­kai and Hawaii island.

The two-year project will include replacing or retrofitting 13,000 light fixtures, installing seven new chillers with state-of-the art compressors and replacing 53 electrical transformers with more efficient models.

The project will result in estimated annual emission reductions of 5.6 million pounds of carbon dioxide, 14,200 pounds of sulfur dioxide and 12,700 pounds of nitrous oxide, according to a news release issued Monday by Ameresco. That’s the equivalent of taking 466 cars off the road annually, according to the news release.

"I commend DAGS and Ameresco for working together in developing a comprehensive efficiency and renewable energy project that is on target with our commitment to energy independence and sustainability," Gov. Neil Abercrombie said in a prepared statement. "Ameresco’s innovative approach will assist DAGS in reaching its energy savings and emission reduction goals."