YARMOUTH — Demand for energy recently awoke a sleeping giant.

Wyman Station, the oil-fired power plant on Cousins Island, was called into service July 18 and 19 to generate electricity for the New England energy market during a period of peak demand, spokesman Steve Stengel said.

The high-energy demand was the result of soaring temperatures that gripped the region for several days in mid-July. In anticipation of the hottest weather, ISO New England, which administers the region’s wholesale electricity markets, launched a voluntary conservation effort.

In a July 16 news release, the nonprofit corporation asked customers to turn up air-conditioner thermostats, turn off unnecessary lights and defer doing laundry until early morning or late evening, along with other suggestions.

At the same time, ISO New England required all power stations to suspend nonessential maintenance to ensure “they were available to us during this time of high demand,” spokeswoman Marcia Blomberg said.

The request came amid a period of extreme heat, including record-breaking temperatures in Maine. On Friday, July 19, coastal Cumberland County was under a heat advisory from the National Weather Service. Heat advisories are declared whenever the heat index — a calculation of heat and humidity — is between 100 and 105 degrees. In Portland, the heat index reached 103 degrees at its peak on Friday. The city also set a record high temperature of 95 degrees for that day.

It was the type of weather that prompts owners NextEra Energy Resources to stoke the aging, inefficient Wyman Station into action.

Stengel wouldn’t say how many days the plant has produced energy in recent years, but it is widely known that the plant sits idle for most of the year, earning revenue simply for its capacity to generate power.

“The station is always hot, spinning and ready to go,” said Nat Tupper, Yarmouth’s town manager for 30 years. “It still has production capability that is significant and it is mostly there for difficult days like we’ve had.”

In April, NextEra disclosed its intent to sell Wyman Station along with Cape Gas, a smaller, oil-fired generator in South Portland, according to a report from the Bangor Daily News. On Tuesday, Stengel told The Forecaster there are no updates on whether potential buyers had expressed interest in the 35-year-old Yarmouth plant.

ISO spokeswoman Blomberg also declined to say how often Wyman Station operates but said oil-fired plants contributed less than 1 percent of power to the New England grid in 2012.

The declining use of the station has led to a decline in Yarmouth’s tax base, Tupper said.

Two decades ago, the station represented more than 40 percent of the town’s value. Now it’s estimated at about 7 percent, he said, and a true value won’t be known until mid-August.

As a result, the town’s tax burden has shifted each year from the plant to residents, but this year’s shift will not be as significant as it was at the onset of the decline 15 years ago, Tupper said.