Energy use on Long Island is projected to continue to decline over the next five years as ratepayers continue to produce their own power and further embrace methods and appliances that cut power use.

A forecast by PSEG Long Island and blessed by the New York Independent System Operator, which oversees state energy markets and publishes the figures, projects total power sales on Long Island to drop to 21,943 gigawatt hours in 2017, and continue downward until 2022.

Meanwhile, the peak summer capacity on Long Island will also continue to stabilize or drop over the period, from 5,438 megawatts in 2016 to 5,414 megawatts in 2022.

Paul Napoli, vice president of power markets for PSEG Long Island, whose staff drew up the forecast, said a range of economic, social and technological factors are built into the forecast, but an overriding factor is the embrace of techniques that cut energy use.

“Energy efficiency has been embraced very, very well,” he said. “It’s a big part of the play.” He noted increases in Energy Star appliances, changes in building codes that “drive more energy-efficient homes,” and modifications to existing homes and commercial buildings as factors.

He also noted Long Island’s embrace of solar energy, particularly on residential rooftops. Customers with solar panels can draw most or all of their power from the systems, reducing overall grid consumption. Long Island this year hit a solar power record of more than 35,000 rooftops, more than any other region in the state. Growth has slowed, however, after the state ended the popular Solar Pioneer rebate program, and increased interest rates for on-bill financing for most customers.

PSEG has been working for nearly two years on a broad assessment of Long Island’s power sources and needs, to determine what will be needed in the future. That plan, called an integrated resource plan, is expected to be completed by year’s end, said Napoli. The plan has repeatedly been delayed, most recently after the Long Island Power Authority and the state requested that PSEG consider scenarios for more wind energy, electric cars and Gov. Andrew M. Cuomo’s Clean Energy Standard, which seeks to have 50 percent of state energy from green power sources by 2030.

“The clean energy standard is a big game changer in how we look at the electric grid,” Napoli said. “What type of renewables and where they will be has a great deal to do with it.”

At least two wind farms are planned for the LIPA service territory, one 11.5 miles from Jones Beach, another off Rhode Island to feed peak-energy demands of the South Fork. If approved, both are slated to be in service by around 2023.

Part of the clean-energy standard is under intense fire from legislators, consumer groups and environmental activists, because half of the 50 percent will come from existing upstate nuclear plants that will receive an estimated $7.7 billion in subsidies over the next 12 years from all state ratepayers. LIPA will pay $45 million a year for these so-called zero-emission credits.

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Napoli declined to discuss any conclusions reached in the integrated resource plan, which lays out a series of scenarios for meeting future needs. But he stuck by a previous PSEG assessment that no new power plants will be needed on Long Island until at least 2028, given the forecasts.

PSEG will present a completed integrated resource plan by year’s end to the state and LIPA, which will make determinations on how to proceed to meet future power projections.

Napoli wouldn’t say which factors precisely were behind the longer-term projection for increased power sales in the region by 2024, but industry watchers say one of them is likely to be a further embrace of electric cars.