Massachusetts Electric Utility Solar Programs: Eversource, National Grid, and Unitil

Massachusetts homeowners and businesses pursuing solar energy interact directly with one of three investor-owned electric distribution companies — Eversource Energy, National Grid, and Unitil — depending on service territory. Each utility administers distinct programs governing interconnection, net metering, and the Solar Massachusetts Renewable Target (SMART) incentive, all under oversight by the Massachusetts Department of Public Utilities (DPU). Understanding how each utility's program is structured, where territories begin and end, and how programs differ in practice is essential before any solar installation moves forward.

Definition and scope

Electric utility solar programs in Massachusetts are the administrative and financial frameworks through which distribution companies manage grid-connected solar generation. These programs cover three primary functions: interconnection (the technical and regulatory process for connecting a solar system to the grid), net metering (the billing credit mechanism for excess generation), and SMART program participation (a declining-block incentive paid per kilowatt-hour generated).

Service territory boundaries define program eligibility:

• Eversource Energy serves eastern Massachusetts including Boston, Cape Cod, and the South Shore, as well as portions of western Massachusetts under its NSTAR and WMECo legacy territories.
• National Grid serves central and northeastern Massachusetts, including Worcester, Lowell, and Lawrence.
• Unitil serves limited areas in Fitchburg, Lunenburg, and several adjacent communities in north-central Massachusetts.

A property's program eligibility is entirely determined by which utility distributes power to that address — not by customer preference. The Massachusetts Electric Utility Solar Programs framework covers only investor-owned distribution companies regulated by the DPU under Massachusetts General Laws Chapter 164. Municipal light plants (MLPs), which serve roughly 40 municipalities including Braintree, Shrewsbury, and Taunton, operate under separate statutory authority and are not covered by these three utility programs. MLP customers should consult their local municipal light board for applicable solar policy.

This page does not address federal-level programs, tax credit eligibility (governed by IRS rules), or program rules in neighboring states. For broader context, the regulatory context for Massachusetts solar energy systems covers the full statutory and administrative framework.

How it works

All three utilities follow a process governed by the DPU's interconnection standards and the SMART program rules established under DPU Docket 17-140-C and subsequent orders.

Standard interconnection process (all three utilities):

1. Pre-application screening — Applicant submits basic project data (address, system size in kilowatts-dc, proposed inverter type) to the utility's interconnection portal.
2. Application submission — Formal interconnection application filed with the utility, accompanied by single-line diagrams and equipment specifications meeting IEEE 1547-2018 and UL 1741 standards.
3. Technical review — Utility engineering staff assess impact on local distribution infrastructure. Systems under 25 kW-ac typically qualify for simplified review (Level 1 or Level 2 screens under DPU standards).
4. Interconnection agreement execution — Upon technical approval, the customer and utility execute a formal agreement specifying operational requirements and any required utility upgrades.
5. Installation and inspection — The solar installer completes physical installation; the local electrical inspector issues a Certificate of Inspection before utility permission to operate (PTO) is granted.
6. Meter configuration and PTO — The utility installs or reprograms the revenue-grade meter to track export and import; PTO letter authorizes system energization.

SMART program enrollment runs parallel to interconnection. Approved systems receive a capacity reservation in one of the program's declining blocks, with the incentive rate (expressed in dollars per kilowatt-hour) locked at reservation. Block sizes and current compensation rates are published by the Massachusetts Clean Energy Center (MassCEC) and updated as blocks fill.

Net metering credit rates differ by utility and customer class. Eversource and National Grid calculate net metering credits at the full retail rate for systems under 60 kW-ac on residential tariffs, consistent with net metering rules in Massachusetts under G.L. c. 164, §138.

Common scenarios

Residential rooftop system (≤25 kW-ac): The most common installation type across all three territories. These systems use the Level 1 interconnection screen and are typically processed within 15 business days under DPU timelines. SMART block compensation applies if capacity remains in the residential blocks for the relevant utility territory.

Commercial system (26 kW-ac to 500 kW-ac): Subject to Level 2 or supplemental review. Eversource and National Grid maintain separate block allocations for larger commercial systems under SMART. Processing timelines extend to 45–90 business days depending on required distribution system studies.

Community shared solar (virtual net metering): Projects up to 2 MW-ac in size can enroll multiple off-takers receiving bill credits through the utility's virtual net metering tariff. Unitil's smaller service territory limits the number of viable community solar sites relative to Eversource and National Grid. The community shared solar in Massachusetts framework applies directly to utility-administered allocation.

Battery storage paired with solar: Each utility requires separate interconnection evaluation for AC-coupled or DC-coupled storage. The Massachusetts solar battery storage systems page covers storage-specific technical requirements that interact with utility interconnection rules.

Decision boundaries

Selecting the applicable utility program depends on service territory only — the utility supplying electricity to the meter governs all program access. Key distinctions between programs:

The SMART program uses separate block structures for each utility, meaning a given block may be fully subscribed at Eversource while still open at National Grid. Project economics depend on which block is available at the time of capacity reservation, not at installation completion.

For system sizing considerations specific to Massachusetts climate and roof conditions, the how Massachusetts solar energy systems work overview provides the technical grounding needed before engaging any utility program. Additional incentive programs layered on top of utility programs — including MassCEC rebates and federal tax credits — are described in the Massachusetts solar incentives and rebates resource available through the Massachusetts Solar Authority home.

Safety standards governing equipment connected to utility grids require compliance with IEEE 1547-2018 for distributed energy resources, NEC Article 690 for photovoltaic systems, and UL 1741 SA for grid-interactive inverters. Each utility's interconnection agreement references these standards as minimum technical requirements. Failure to meet them results in denial of permission to operate, regardless of local permit status.

References

• Massachusetts Department of Public Utilities (DPU) — Regulatory authority over Eversource, National Grid, and Unitil; administers interconnection and net metering rules under G.L. c. 164
• Massachusetts Clean Energy Center (MassCEC) — SMART Program — Official SMART block status, compensation rates, and program documentation
• Eversource Energy Interconnection — Eversource distributed generation interconnection portal and application materials
• National Grid Distributed Generation Interconnection — National Grid interconnection process documentation for Massachusetts customers
• Unitil Distributed Generation — Unitil interconnection and net metering information
• IEEE 1547-2018 Standard for Interconnection and Interoperability of Distributed Energy Resources — Technical standard referenced in DPU interconnection requirements
• Massachusetts General Laws Chapter 164, §138 — Statutory basis for net metering in Massachusetts