Massachusetts MLP solar interconnection is where IOU muscle memory wastes a week. If the bill says Wellesley Municipal Light Plant, Concord Municipal Light Plant, Belmont, Braintree, Holyoke, Reading, Taunton, or another light plant, PowerClerk will not help you. DPU’s interconnection page is about Eversource, National Grid, and Unitil tariffs. The light plant has its own application, its own meter rules, and its own written authorization. Draw to that document.
Athol Energy still produces the AHJ set the building department wants: site plan, roof plan, attachment layout with dimensions, electrical single-line with conductor and conduit notes, cut sheets, placards. Then we add the MLP’s extras instead of pretending Exhibit A is universal. 20,000+ residential projects and 200 MW+ designed with 30+ installer partners includes crews who run IOU towns and MLP towns in the same week. That is exactly how the wrong portal gets a file.
Massachusetts MLP solar interconnection is a different utility
Read the bill first. Community aggregation on an IOU meter is still an IOU meter. An MLP is a different company. Mass.gov interconnection materials will not list WMLP’s email. Wellesley’s published interconnection page tells installers to submit the application and agreement to named WMLP staff, with site and rooftop plans showing module locations, inverters, AC disconnect, utility and solar production meters, electrical service panels, and kW-DC and kW-AC capacities, plus a one-line and cut sheets. If there is a battery, WMLP wants the backup supplemental form. Combined solar-plus-storage kW-AC governs Simplified vs Standard and net-metering eligibility on that policy. [CONFIRM AS OF 2026-09-19]
Wellesley’s January 2022 interconnection policy (public PDF) describes Simplified as listed inverter-based 10 kW AC or less single-phase or 25 kW AC or less three-phase, with no application fee on Simplified, and Standard as everything else with fees case by case. That is not M.D.P.U. 1632’s 25 kW single-phase Simplified language. Do not quote Grid thresholds on a Wellesley proposal. After approval, WMLP issues Approval to Install. Energizing still waits for WMLP’s authorization language. A building permit is not that letter.
Concord is not Wellesley
Concord’s public solar page tells installers to email the interconnection application with related documents to CMLP. They want a production meter socket on every solar project, either a production meter (for Class I REC sale) or a weatherproof cover and jumpers. They prefer three-line drawings in all cases and require them for batteries. Specification sheets for modules, inverters, and ESS. Rebate paperwork is separate from interconnection. Net metering policy acknowledgements are separate again. Concord’s residential net metering policy (effective 4/9/2025) caps generating capacity at 167 kW AC and adds export limiter and/or battery rules as site capacity steps past 25 kW and 50 kW. If you are over those lines, the SLD has to show the limiter or the controllable battery. A pretty IOU Simplified sketch will not. [CONFIRM AS OF 2026-09-19]
CMLP’s published rebate ($625 per kW DC, capped at $3,125 per service address on the page we opened) is not SMART. Do not mix CLEAResult SOQ language onto a Concord cover. Do not invent other MLP rebate amounts. If you are in Holyoke or Taunton, open that light plant’s document. Athol will mark [NEED SOURCE] rather than guess a dollar.
What the AHJ set still has to do
The building department in an MLP town is still an AHJ under 780 CMR and 527 CMR. Fire paths, snow load, and attachment dimensions do not disappear because the utility is municipal. File the town set and the MLP application from one SKU list. If Concord requires a three-line for a battery, the town electrical inspector should see the same battery. Athol’s permit design and interconnection desks stay on that list. Statewide IOU context is on Massachusetts solar design services. It does not override WMLP or CMLP.
PE stamps remain local. Some MLP applications will accept unstamped residential diagrams. Concord’s three-line preference is not automatically a PE seal. If the building department asks for a Massachusetts PE, we coordinate that on the AHJ set, wet or digital as they accept. Do not seal an IOU typical and write “MLP” in the title block.
How MLP jobs fail
They fail when the PM files Eversource because the last ten jobs were Eversource. They fail when production meter sockets are omitted on Concord. They fail when Wellesley Simplified is quoted at 25 kW single-phase. They fail when SMART is promised on an MLP bill. They fail when the town fire path cuts modules and the light plant application still shows the old kW. Fix the application the same day.
Authorization to interconnect is still written. Do not energize on a town sticker. If the array moved, as-built for both the building department and the MLP. Phone +1 (209) 266-2669 when the bill says a light plant and your folder still says PowerClerk.
Intake questions that prevent an IOU filing
Ask for a bill PDF, not a town name. Concord the municipality and Concord Municipal Light Plant are related in geography and still two desks. Wellesley building and WMLP are two desks. If the customer is on community aggregation in an IOU town, they are not on an MLP. If they forwarded a municipal light bill, PowerClerk is the wrong folder. Put the MLP name in the title block in the same size as you would put Eversource. Small type is how a drafter misses it at 6 p.m.
Ask what the light plant wants for meters before you copy a Simplified IOU sketch. Concord’s production socket is a construction item, not a closeout surprise. Wellesley’s plan callouts for kW-DC and kW-AC on the site plan are a first-upload item. If a battery is in contract, pull that MLP’s storage supplement the same day you pull the PV application. Combined kW may kick you from Simplified to Standard on Wellesley even if the PV inverter alone would have qualified. Write combined kW on the cover so sales sees it.
Other MLPs (Belmont, Braintree, Holyoke, Reading, Taunton, and the rest of the Massachusetts public-power map) get their own PDFs. We will not invent their forms. Send us the application they emailed you, or the URL they published. If they have no public PDF, we will mark [NEED SOURCE] and ask the PM to obtain the document rather than guess a fee. Guessing is how you collect the wrong check.
Building-department fire paths still apply. 527 CMR 1.00 does not pause for public power. If a 36 in. path cuts modules, the MLP application kW changes. If the light plant requires export limiting above a kW step, the SLD shows the limiter. A massachusetts mlp solar interconnection packet that hides the limiter in an email will fail the witness or the meter tech, whichever arrives first. As-builts still matter. Authorization is still written. Town stickers still do not energize.
SMART language stays off MLP covers unless that plant is somehow an EDC in SMART, which residential crews should not assume. Local rebates have their own shade calculations and terms. Concord publishes rebate math. Do not paste it onto Wellesley. Do not paste SMART 3.0 reservation language onto either. If the light plant emails a unique one-line sample, draw to that sample and keep a copy in the job folder so the next PM does not file Exhibit A by habit.
Installer questions on MLP weeks
Is MMWEC or ENE the interconnecting utility?
Those organizations may touch rebates or supply. Interconnection is still the local light plant unless that plant’s document says otherwise. [CONFIRM AS OF 2026-09-19]
Can we use a DPU Simplified form as a template?
Only as a reminder of topics (meters, disconnects, listings). The MLP’s own application is the legal form. Copying Exhibit A into a Wellesley email is a bounce.
Do MLPs use PTO language?
They use their own authorization words. Treat that letter like PTO. Do not energize without it.
How do we start?
Send the bill, the MLP name, equipment list, and AHJ. Use contact. The next massachusetts mlp solar interconnection packet should name that light plant on every sheet, including the meter sockets they actually require.