PROVIDENCE — Greenhouse gas emissions from Rhode Island’s five natural gas-fired power plants are on the rise.

According to new data released by the Environmental Protection Agency, emissions from the state’s major power plants increased by more than a million short tons last year, largely due to heightened activity in the regional electric grid. Four out of five facilities that reported data saw emission increases between 52% and 72%.

In raw terms, in 2022 the five power plants produced just about 3 million short tons of GHG emissions, and about 4 million short tons in 2023.

The five facilities, which include the Manchester Street Power Station in Providence and the Rhode Island State Energy Center in Johnston, are some of the biggest GHG emitters in the state, and are required by federal law to report their emissions annually to the EPA.

The reason for the big increase in emissions? State officials say retirements of other power plants in New England often result in ISO New England, the entity that manages the electric grid in the Northeast, to ask more of Rhode Island’s natural gas plants.

“It’s positive to see coal and oil power plants shutting down in our region, which is a testament to the changing market,” DEM spokesperson Evan LaCross said. “But it requires ISO New England to rely more heavily upon its existing fleet, although renewables are increasingly being used as well.”

LaCross also said Rhode Island’s five natural gas plants are typically asked to produce more electricity, due to their ability to provide cost-effective power. Around 35% of all electrical demand in New England is met by natural gas, according to ISO New England data.

Since 2018, three major power plants have been retired from the New England electric grid, including two coal-fired plants (Connecticut’s Bridgeport Harbor Station and Massachusetts’ Mount Tom Station) and the Pilgrim Nuclear Power Station in Plymouth, Mass. Together all three plants produced 1,200 megawatts (MW) of power. A total of 7,000 MW of coal, natural gas, and nuclear plants have left the regional grid since 2013.

Much of the replacement power coming online in the regional electric grid will be renewable energy. The vast majority of new projects in ISO New England’s interconnection queue are wind, solar, and battery storage projects, and Rhode Island, along with its neighboring states, have renewable energy standards that will increase capacity.

(Rhode Island’s renewable energy standard, updated in 2022, requires 100% compliance by 2033.)

But the increased emissions from the five power plants are unlikely to impact the Ocean State’s climate reduction mandates. DEM has calculated electricity emissions not by how much power is produced in Rhode Island, but by how much Rhode Islanders across the state consume on an annual basis.

The state’s Executive Climate Change Coordinating Council (EC4) endorsed consumption-based accounting in 2016, primarily to keep regional consistency when calculating emissions, as Massachusetts and Connecticut already crunched their emissions numbers that way.

LaCross said Rhode Island primarily relies on the Regional Greenhouse Gas Initiative (RGGI), an 11-state cooperative, to lower its power plant’s emissions. The program operates by setting emission limits to power plants across participating states, and auctioning carbon allowances for facilities that exceed their limits. States are given a share of the proceeds to use on climate mitigation projects.

“Since 2005, the RGGI states have reduced annual power sector emissions 50%, which is almost 50% faster than the nation as a whole, and have raised over $7 billion to invest into local communities,” LaCross said.

The state used proceeds from auctions last year to give an operating budget to the EC4, the state’s designated agency on climate change response.