The ISO-NE cluster request window is not the October 20 agreement negotiation. A Massachusetts developer with a transmission-level project has two ISO-NE dates on the same fall calendar, and they are not the same job. October 20, 2026 ends the negotiation period on draft interconnection agreements from the transitional cluster. November 19, 2026 closes the window for a project entering the first regular cluster. One date is about an agreement already tendered. The other is a drawing freeze on a request that still has to arrive complete.
The window opened on October 5, 2026. It runs 45 calendar days and closes at the end of the day on November 19. An interconnection request that is still incomplete when that day ends is withdrawn. There is no further chance to cure after the close.
Two clocks on one Massachusetts desk
The transitional track is already past the study. The Transitional Cluster Study final report was August 6, 2026. Draft interconnection agreements were tendered August 21, 2026. The negotiation period ends October 20, 2026. On that date the customer has to request to execute the agreement, request that it be filed unexecuted, or enter dispute resolution. If none of those three happens, the request is deemed withdrawn. That file belongs with the earlier piece on transitional cluster interconnection agreements. This post stays on the new window.
A project that is just now entering the cluster is not marking up an agreement. It is trying to get a complete request accepted before November 19. ISO is accepting those requests in GridUnity GridInterConnect for Transmission, called GIC-T. Split the folders. The October 20 file is an agreement. The November 19 file is the point of interconnection, the one-line, the site plan, the inverter and transformer data, and the AC size that will be studied. Pulling megawatts off an old transitional model puts the wrong size into GIC-T.
What the ISO-NE cluster request window actually freezes
While the window is open, ISO acknowledges receipt within 5 business days and can notify the customer of deficiencies. The customer then has 10 business days after that notice to cure, and the cure also has to land not later than the close of the window. Both limits apply. A deficiency notice that shows up in the second week of November does not create ten business days past November 19. The calendar wins.
If the customer does not cure, the request is withdrawn and $5,000 of the interconnection request deposit is forfeited. That forfeiture is the dollar figure tied to a missed cure. Keep that separate from the other rule: a request that is still incomplete at the close is withdrawn, with no further chance to cure.
Anything ISO can mark deficient has to be checkable in the first upload, because the cure can be shorter than ten business days when November 19 is close. A site plan that never names the point of interconnection, a one-line whose AC size does not match the form, or inverter data that still says "or equal" is a gap. Athol Energy prepares the interconnection drawings, permit design, and PE stamping for that freeze, for installers and developers in Massachusetts, Rhode Island, Connecticut, New York, and Pennsylvania. The work product is the set a developer can file and then stop editing.
Five drawing items that have to match
A normal interconnection request needs the electrical and site information the study will use. Freeze the items below before the GIC-T upload, and keep them identical on the form and on the sheets.
- Point of interconnection. Use the same words on the site plan and in the request. "Along the rear line" and a named structure are two projects.
- One-line. Show the path from the inverters through the transformer to the point of interconnection, and label the AC size that will be studied. If export will be limited, show that size and the equipment rating as separate numbers.
- Site plan. Show the array, the equipment pad, the point of interconnection, and enough of the parcel to identify the site.
- Inverter and transformer data. Model, quantity, and the ratings the request asks for. A placeholder model waits on a datasheet that may miss the cure window.
- AC size that will be studied. This is the number ISO will carry. Changing it after the window describes a different request.
Before upload, write a job-folder note that is not an ISO form. Copy the point of interconnection from the site plan and from the GIC-T field. Write the studied AC size, the inverter manufacturer, model, and quantity, the transformer rating if one is in the request, and the drawing revision and date. If any line is blank on November 18, the request is not ready. A cure depends on ISO sending a deficiency notice, and the answer still has to arrive before the window closes. PE stamping belongs on the revision you are filing. Stamp the matching set, then stop editing the AC size.
Different megawatts on the permit set and the request
ISO will study the size on the request. A permit set drawn for a larger array, then left alone after procurement cut inverters, is a second project. The building department is a different portal. The authority having jurisdiction will review the size on the permit set. If those megawatts differ, you have two descriptions. A later as-built will not erase that if the study, the agreement, and the permit were never about the same AC size. Put the studied size on the one-line, the site plan equipment schedule, the GIC-T request, and the permit set before November 19. If the permit is already in review at the old size, say so in the job note. Permit design and the cluster request have to move as a pair.
Commercial and utility plan sets break this way when a civil sheet, an electrical sheet, and the application are edited by different people. Freeze a revision block and put the studied AC size in it. If inverters change after the freeze, revise every sheet that states kilowatts or megawatts, and check the GIC-T fields again before the window closes. A new inverter count with the old transformer rating still on the one-line is the same error as two AC sizes.
What starts when the window closes
The Customer Engagement Window begins when the Cluster Request Window closes on November 19, 2026. It is not a second chance to finish a deficient request. Incomplete at the close means withdrawn, with no further cure. If the module count is still moving on November 18, the AC size in the request is whatever you upload. A later change is a new conversation with ISO, not a quiet sheet swap.
ISO's participation forum lists October 17, 2027 as the date ISO posts the Cluster Study Report. That date is a planning marker only. Drawings due now support the request. They should not quote an upgrade cost or a study result, because that report has not been posted. A distribution application at National Grid, Eversource, or Unitil is a different filing from a GIC-T cluster request. Use this package for the transmission-level project that is actually entering the window. Massachusetts solar design and interconnection drawings keep the permit set and the GIC-T package on one AC size.
Write down which track the job is on. A blank point of interconnection or a blank studied AC size on November 18 will not become a fact on November 20.