The approval process for large renewable energy projects is expected to take longer because of fears about the burden of solar and offshore wind on the region’s electricity transmission system.

In meetings this summer, National Grid and ISO New England, the operator of the regional electric grid, told renewable energy developers in Massachusetts and Rhode Island that the application review for connecting to the grid would be extended while studies of regional power transmission systems are conducted.

The delay impacts projects that were once considered too small to require interconnection reviews, as projects between 1 megawatt and 5 megawatts will now be paused under the enhanced scrutiny. If the study finds that the projects cause cumulative impacts on the power grid, the developers will need to conduct a transmission study. In Massachusetts, some 200 applications will be delayed pending the study. Rhode Island has 87 pending applications.

Smaller commercial and residential projects will not be delayed by the review.

Developers are already experiencing lengthy waits in National Grid’s so-called “interconnection queue,” because of the influx of large solar systems, mostly being built in rural parts of Massachusetts and Rhode Island where outdated infrastructure is ill-equipped to manage the inflows of electricity.

The distribution problem is further complicated by the anticipated flood of power from offshore wind facilities, which will be delivered via high-voltage power lines through Narragansett Bay and come ashore in North Kingstown and at the former Brayton Point coal-fired power plant in Somerset, Mass.

“That power has a ripple effect on the grid,” said Chris Kearns, chief of program development for Rhode Island’s Office of Energy Resources.

ISO New England expects the growth of utility-scale solar and offshore wind to continue in the energy mix.

“Both will need to be studied in a coordinated fashion to ensure that they will be able to come on-line and operate without having an adverse effect on the regional system, while at the same time ensuring continuing reliable service to the existing electricity customers in the area,” said Marcia Blomberg, spokeswoman for ISO New England.

The “cluster studies” will look at substations and other infrastructure in less-developed regions such as Washington and Kent counties in Rhode Island and central and western Massachusetts. These areas are shifting from a low-energy electric distribution system supported by remote, conventional power plants to a distributed generation system with multiple renewable-power sources of all sizes.

“We are transitioning to a renewable energy system from a system built back in the ’70s and ’80s,” Kearns said.

Massachusetts is expected to have part 1 of its cluster studies done in November. Part 2 is scheduled to competed in early 2020. The Rhode island studies are scheduled to completed by the end of next year’s first quarter.

The Rhode Island Public Utilities Commission is expected to open a docket later this year that will explore ways for National Grid to speed up the review process. A bill (S0959) mandating an interconnection analysis of about 90 days nearly passed the General Assembly in June. It was approved by the Senate but the 2019 legislative session ended before the House could hold a hearing.

The Massachusetts Department of Public Utilities (DPU) initiated a review of the interconnection issues in May. The docket will review National Grid’s affected system operators (ASOs) and the role of energy storage in reducing the need for interconnection upgrades and alleviating delays.

In a letter to the DPU, the Massachusetts Department of Energy Resources (DOER) noted that renewable projects with signed interconnection agreements are in jeopardy because of delays caused by the ASO studies.

DOER has urged National Grid not to send interconnection requests to ISO New England for the smaller, non-utility renewable projects that typically don’t burden the power grid.

“National Grid should resolve the causes of interconnection delays for those projects that are mechanically complete as quickly as possible, and without further delay,” DOER’s deputy general counsel Ben Hobbs wrote in the Aug. 2 letter.

DOER said it may direct National Grid to write timelines and corrective plans for projects that aren’t addressed in the studies.

The Massachusetts attorney general’s office also has urged utilities to inform developers of interconnection delays and to offer a website offering changes and updates.

Developers, who have long complained about the lengthy grid connection process, say securing the interconnection agreement adds nine to 12 months to a project. Pausing for the new studies will likely jeopardize solar and wind development, they said.

In comments to the DPU, developers said National Grid is imposing unnecessary administrative delays. The utility slows interconnection studies by labeling applications as complex, not signing documents, arbitrarily revisiting applications, and adding new costs to the interconnection work, according to energy developers.

Developers want utilities to allow more use of battery storage and other technologies that can ease the burden on the regional transmission network. They also want timely information regarding their interconnection applications, preferably posted online.

National Grid has, so far, created websites of the studies for Massachusetts and Rhode Island.

National Grid is scheduled to host an Aug. 13 meeting for its cluster study in Massachusetts.