WESTBROOK — The city has contracted with a company to build a solar array that will power all city and school buildings and could save the city $3.5 million over the next 30 years.

C2, an energy company out of New York, is expected to have the solar array at the Sandy Hill landfill off Saco Street built in the next 12 to 14 months, according to Mayor Mike Foley. The company was chosen by both city and school administration.

The contract locks the city into the same power rate for 30 years, presenting long-term savings.

The city also plans to lease land to C2 for a solar field near the Rocky Hill Landfill off Methodist Road that would serve residents. Those plans will shape up further down the road, city officials said.

The size, design and cost of the Sandy Hill solar array are still in the planning phases, but the project should come at no added cost to the city, Foley said.

“We’ve signed a letter of intent to develop the concrete figures and designs of the system, and at the same time to develop ordinances that better support solar,” Foley said about the municipal array.

The 30-year agreement locks in “an electricity rate at just below what we have been paying, which is the lowest rate I’ve seen for us in 15 years and far below standard offer,” said City Engineer Eric Dudley. “I see the lease income as the real savings but it is too early in the process to talk specific numbers.”

Compared to the price of solar elsewhere in the state, the city’s rate will be less expensive, Dudley said.

“Typically, with solar, your per (kilowatt hour) charge is closer to $0.10,” he said. “The agreement that we are entering into with C2 is $0.0622/kWh, which is an almost imperceptible saving over what we currently have but the best solar rate we are aware of in Maine.”

On average, the city and schools use about 7.6 million kWhs per year.

According to Dudley, the best way to gauge savings is by estimating that electricity supply costs increase at 1.5%.

“With a fixed rate for 30 years, we will avoid this annual cost increase, which would result in a savings of $3.5 million over the life of the contract,” he said.

Savings aside, officials said the change is important in leading by example when it comes to sustainability.

School lessons and lab work focusing on solar power are already being developed at the high school, Superintendent Peter Lancia said.

“This is a wonderful opportunity for our school department, especially for our students and teachers. It will realize cost savings in years to come, but it will also provide a functioning learning lab at Westbrook High School,” Lancia said.