Two Maine energy companies are teaming up to promote each other’s services in a partnership that may seem counter-intuitive at first — one is an oil, propane and biofuel provider, while the other is a solar energy company.

Brunswick-based Downeast Energy and ReVision Energy, which has offices in Portland and Liberty, said their new agreement would allow each company to offer more energy alternatives to their customers.

Mike McCormack, vice president of sales and marketing for Downeast, said the company’s customers have been asking about solar energy water heater systems with more frequency, both in surveys and in their contact with employees.

Downeast chose to seek an expert partner rather than build the solar capacity in-house, and McCormack approached ReVision, he said.

The partnership between a more traditional energy and an alternative energy firm may be seen as counterintuitive, said Phil Coupe, ReVision co-founder. After all, many seek solar or other energy resources to get away from fossil fuels.

“The reality is, everyone in Maine needs traditional fuels to make it through a Maine winter,” said Coupe.

In this agreement, Downeast can give more of their customers what they want — a broader array of energy solutions, including solar. And ReVision gains access to a much larger market. While ReVision has installed between 2,500 and 3,000 solar energy systems, mostly in Midcoast Maine and greater Portland, Downeast has 50,000-plus customers in the same geography.

ReVision has been training Downeast’s 300 employees for the past three weeks about the solar energy systems — what makes a home a viable candidate for solar hot water, what the physical space needs are, etc. The companies will market their energy offerings together.

If a customer calls Downeast and asks about solar, the company will be able to offer it through ReVision. Likewise, said Coupe, if ReVision technicians are in a home, they can suggest the homeowner consider Downeast’s biofuel product to save on oil.

There’s no money, no ownership stakes in each other’s firms, no extra finder’s fees for business generated — this is just a marketing-expertise agreement.

Coupe and McCormack said they believe this sort of partnership between solar and a more traditional energy company is unique in northern New England. McCormack said this latest move is part of the continuing evolution for Downeast, which was founded as Brunswick Coal in 1908 and sold coal and firewood.

“We don’t deliver coal or firewood anymore,” said McCormack.

Over the past decade and a half, the company has worked with customers to actively reduce the amount of fuel they consume, said McCormack, in many cases through improving the technology in their homes. The company recently trained employees in energy auditing, so they could improve the efficiency in all parts of a customer’s home, he said.

“We truly view ourselves as an energy company,” said McCormack.

That’s a business stance that many traditional home-heating oil companies have taken in recent years. Time and again, “oil” has been dropped from company names, and “energy” has been added, with firms offering biofuels, propane and, now, solar.

“You want to be there when the customer asks, and you want to be able to offer them whatever they want. I think that’s where Downeast has gone,” said Jamie Py, president of the Maine Energy Marketers Association.

That trade group used to be called the Maine Oil Dealers Association, until it changed its name two years ago.

According to Coupe, a solar hot water system can provide all the hot water for a typical home in the summer months. That declines in the spring and fall, and over the winter. The system costs between $10,000 and $11,000 gross; with rebates and tax credits, about $6,500. The typical system pays for itself in about six years, he said.