Utilities · Massachusetts

National Grid Massachusetts: solar on the 40 cent grid

SLWritten by the Solar Learning Lab research desk·Updated August 18, 2026·9 min read

Add National Grid's published delivery total to the fixed supply price that took effect August 1, 2026 and you get 40.12 cents per kilowatt-hour. That is the highest all-in residential price of any utility we cover, higher than PG&E's baseline tier, higher than Eversource next door. It is a miserable number to pay and a remarkable one to offset, because in Massachusetts the net metering credit tracks those same charges. The economics of a National Grid roof are the strongest in our entire directory, and the fine print below is where quotes go wrong.

Net metering under the 2026 tariff

National Grid's net metering provision was refiled this year, effective March 1, 2026. The homeowner-relevant core: a solar facility of 25 kW AC or less is Nameplate Cap Exempt and earns the standard credit computed from the basic service, distribution, transmission, and transition charges. Credits carry forward from billing period to billing period, and in a month where the system generates more than the house uses, no kWh bill issues at all. The energy efficiency charge, renewable energy charge, SMART factor, EV program factor, and the net metering recovery surcharge are all excluded from the credit.

Run the current numbers through that formula and one exported kilowatt-hour is worth 17.185 plus 11.028 plus 5.464 minus 0.029, roughly 33.65 cents. That is our arithmetic, not a published National Grid credit rate, and the same caveat we put on the Eversource page applies here. But even with margin for interpretation, an export credit in the low 30s against a 40 cent retail price makes oversized self-consumption gymnastics unnecessary. In this territory, unlike California's net billing regime, a plain grid-tied system without a battery still pencils, and the battery is an income add rather than a rescue.

Sources: M.D.P.U. No. 1625 net metering provision and the Mass.gov net metering guide. Credit value is our sum of the cited components.

SMART 3.0 stacks on top. The DPU approved the redesign May 19, 2026: 600 MW of program-year capacity, applications open through December 31, a flat 3 cents per kWh for residential systems of 25 kW or less, 6 cents low income, plus adders like 4 cents for storage. National Grid's SMART tariff on file dates to January 1, 2026, and whether a superseding 3.0 tariff has been filed is one of the items we could not verify below.

Sources: Mass.gov SMART 3.0 program details and Solar Power World.

Interconnection and the threshold caveat

The Simplified application for a listed small inverter system costs $28, with a free witness test. Larger or non-qualifying projects pay $4.50 per kW between a $300 minimum and a $7,500 cap, and tariff timeframes count in business days. Cap allocation, where it applies, comes after engineering review and requires an executed interconnection service agreement; paying an invoice does not hold your place.

Here is the caveat worth reading twice. National Grid's posted interconnection tariff still lists Simplified eligibility at 15 kW for single-phase systems. The state model tariff approved February 10, 2026 raised that threshold to 25 kW, National Grid filed its company-specific version on February 25, and the DPU stamp-approved the utilities' tariffs April 27, 2026. The governing standard is 25 kW; the stale PDF is not. A 10 kW rooftop was always fine either way, but an installer sizing an 18 kW system off the old document could route you into the wrong process. If a proposal cites the 15 kW limit, that is a currency check on the rest of it.

Sources: the M.D.P.U. 1620 fee schedule (see the threshold caveat above before relying on its eligibility limits), D.P.U. 26-32 notice, Mass.gov utility interconnection, and the MassACA FAQ. The proposed $225 Simplified fee in D.P.U. 26-57 would apply to National Grid as well and was not approved as of our review date.

For who should build the system, our installer profiles grade every major Massachusetts company on documentation, complaint history, and verified volume, and the Massachusetts guide carries the statewide economics these rates feed into.

What we could not verify

As of August 18, 2026: a National Grid published residential net metering credit value in cents per kWh, so our 33.65 cent figure is component arithmetic; whether a superseding SMART 3.0 tariff has been filed and approved; whether the proposed $225 interconnection fee in D.P.U. 26-57 was approved; the approved value of the October 2026 performance-based rate adjustment; a typical residential interconnection timeline end to end; and a residential hourly time-of-use tariff, which does not appear to exist yet. Where we could not read a source, we did not print a number. Our editorial policy explains how corrections work if you hold a document that settles any of these.