Massachusetts Plug-In Solar Laws
By Daniel Okafor · Last reviewed In short: Massachusetts has not enacted a statewide plug-in solar exemption. The House passed H.5175 and the Senate passed a different S.3166 text, but both bills entered conference on July 16, 2026. Neither proposal is current permission. Follow the existing utility, electrical, property and local process while the conference committee works.
Current status
Different bills in conference
Both chambers passed legislation, but they did not agree on one text. A conference committee must resolve the differences before any final bill can advance. Follow the rules in force today.
Key facts
- Status: House and Senate versions are in conference, not enacted
- House vote: H.5175 passed 128-27 on February 26, 2026
- Senate vote: amended text passed 32-8 on July 1, 2026
- House proposal: no more than 1,200 W through a standard 120 V outlet
- Senate proposal: 391 W threshold for the specific listing exemption and notice within 30 days
- Current route: written utility interconnection approval before connection
Check your location
Framework status and exact product eligibility are separate checks.
What this means today
The two branches have not yet agreed on a Massachusetts plug-in solar bill. The House passed H.5175 in February. The Senate replaced it with a different proposal in July. On July 16, the House declined to concur, the Senate insisted on its amendment and both branches appointed a conference committee. At review, the official record showed no conference report or enacted act.
The House text covers a device up to 1,200 W. The Senate uses a different definition, a 391 W threshold for one product-listing exemption, notice within 30 days and tenant-related provisions. Until a final text passes and becomes law, follow the Massachusetts Department of Public Utilities process already in force.
Current rules versus the two passed proposals
| Question | What applies today | House H.5175 | Senate S.3166 |
|---|---|---|---|
| Legal status | No enacted statewide plug-in-specific exemption appears in the reviewed official record. | Passed the House, then replaced by a Senate amendment. | Passed the Senate; the House did not concur. Both versions are in conference. |
| Output wording | No plug-in-specific watt exemption is in force. | No more than 1,200 W maximum power output. | 391 W maximum output to a standard outlet for the specific subsection (c) listing exemption. |
| Connection | Ask the utility for an Interconnection Service Agreement and Authorization to Connect. | A qualifying device would use a standard 120 V AC outlet. | A defined plug-in PV system would connect through a standard electrical outlet. |
| Utility step | Written utility approval applies under current DPU guidance. | No prior approval, related fee or extra utility control for a qualifying device. | No prior approval, application, agreement, study, fee or extra control; notice within 30 days for the subsection (c) route. |
| Product evidence | Current code, tariff and exact equipment requirements control. | UL or equivalent NRTL certification, outage protection and the most recent NEC. | UL or equivalent NRTL certification; inverter shutoff after 0.2 seconds after a power disruption. |
| Export | Meter and tariff treatment require a utility-specific answer. | The device would be exempt from net-metering requirements. | An eligible system could not be used in net metering. |
| Property | Lease, condominium, mounting, building and local approvals remain separate. | No tenant installation right appears in the cited plug-in provisions. | Tenant and unreasonable-restriction clauses use terms whose final scope is unresolved. |
What H.5175 / S.3166 says
H.5175 defines a device up to 1,200 W using a standard 120 V AC outlet for onsite consumption, with outage, NEC and UL or equivalent NRTL conditions. S.3166 uses a different definition, a 0.2-second inverter shutoff, a 391 W threshold for one product-listing exemption and notice within 30 days. A conference committee must produce one final text before enactment.
Read the official bill record ↗
H.5175 and S.3166 timeline
| Date | Official event | What it means |
|---|---|---|
| February 26, 2026 | House passed H.5175, 128-27 | The House approved its 1,200 W proposal; it did not become law. |
| July 1, 2026 | Senate substituted S.3166 and passed, 32-8 | The Senate approved a materially different plug-in solar route. |
| July 16, 2026 | Conference committee appointed | The House did not concur; each branch assigned three members to seek one bill. |
| August 11, 2026 | Status reviewed | The official record showed no conference report, final passage or enactment. |
Why conference status matters
The chambers passed different language. The House must concur in the Senate amendment, or both branches must approve one conference report. The July 16 history records House non-concurrence, Senate insistence and conference appointments. Every threshold and exemption remains proposed until the official record shows final passage and enactment.
There is no single proposed watt cap for Massachusetts. The House version uses 1,200 W. The Senate's 391 W figure applies to its subsection (c) product-listing exemption. Neither is a settled state rule.
The current route still starts with utility approval
Massachusetts DPU guidance says distributed generation needs written utility approval before connection: an Interconnection Service Agreement followed by Authorization to Connect. Eversource, National Grid and Unitil use DPU-approved tariffs; municipal utilities may have their own process.
Send the serving utility the exact model, maximum continuous AC output, plug and circuit method, anti-islanding evidence, mounting location and proposed meter behavior. Request a written response tied to the address and configuration.
The 1,200 W and 391 W figures are not interchangeable
H.5175 sets maximum power output at no more than 1,200 W; it does not describe that figure as combined panel DC nameplate capacity. Check panel DC, inverter continuous AC and any grid-directed limit separately.
S.3166 uses 391 W only in the subsection exempting an eligible system from product-listing provisions that would require alterations to premises, wiring or electrical panels. It also allows one or more eligible systems at a service address. The final effect of those clauses remains unresolved.
Neither bill names UL 3700
The House version requires UL or equivalent NRTL certification plus outage and NEC conditions. The Senate version also uses UL or equivalent NRTL certification and requires inverter shutoff after 0.2 seconds after a power disruption. Neither cited provision names UL 3700.
UL 3700 remains an Outline of Investigation for complete plug-in photovoltaic systems. A UL 1741 inverter listing provides component evidence, but does not prove that the complete configuration satisfies either proposal. Match the panels, inverter, cable, plug, controls and instructions to a public testing-laboratory record.
Mass.gov identifies 527 CMR 12.00, based on the 2023 National Electrical Code, as the current code source reviewed here. Its separate 2026 amendment document is labeled proposed.
Export and property rights remain separate decisions
The House version would exempt a qualifying device from net-metering requirements. The Senate says an eligible system may not be used in net metering. Under current rules, the utility tariff controls meter and export treatment. Base the value estimate on self-consumption unless a credit is documented.
The Senate proposes tenant and unreasonable-restriction clauses but uses 'portable-scale solar generation device' and 'small portable solar generation device' instead of its defined 'plug-in photovoltaic system.' Their scope remains unresolved. Massachusetts General Laws chapter 184, section 23C does not provide automatic permission to alter a rental, balcony rail, facade, common area or electrical installation. Get a property-specific written decision.
Your serving utility still matters
Current Massachusetts DPU guidance requires a written Interconnection Service Agreement and Authorization to Connect before distributed generation connects. H.5175 and S.3166 propose different exemptions, but the official record shows them in conference rather than enacted.
Pre-purchase checklist
- 1Open the official H.5175 history and confirm whether a conference report or later action has appeared.
- 2Read both H.5175 and S.3166 rather than treating either chamber's watt figure as final law.
- 3Identify the serving utility and request its current interconnection application, agreement and Authorization to Connect process.
- 4Record panel DC capacity, every inverter's continuous AC output and maximum output through the proposed outlet.
- 5Verify the exact NRTL record, outage behavior, plug, cable, circuit method and manufacturer instructions for the complete configuration.
- 6Ask the local electrical, building, fire and structural authorities which approvals apply, and obtain written property approval for the exact mount and cable route.
- 7Confirm meter behavior and model savings from self-consumption unless an approved tariff establishes export credit.
- 8Do not connect under a proposed exemption unless one final bill is enacted and in force.
Next steps
Primary sources
Frequently asked questions
Is plug-in solar legal in Massachusetts right now?
Massachusetts has no enacted statewide plug-in-specific exemption in the reviewed official record. H.5175 and S.3166 are different chamber texts in conference. That does not prove every configuration is prohibited. It means neither proposal supplies current permission, so the existing utility, electrical, local and property requirements must be checked before connection.
Is the Massachusetts proposal 1,200 W or 391 W?
Both numbers appear, but in different bills and for different tests. House H.5175 defines a portable device with no more than 1,200 W maximum output. Senate S.3166 uses 391 W for a specific listing exemption tied to building alterations. Neither value is current law, and no single final conference definition exists yet.
Would a Massachusetts plug-in system need utility approval?
Today, yes under the reviewed Massachusetts DPU guidance: obtain a written Interconnection Service Agreement and Authorization to Connect before connecting distributed generation. Both proposals would remove specified prior-approval and interconnection steps for qualifying systems, but those exemptions are not enacted. Use the serving utility's process for the exact system and address.
Would Massachusetts require UL 3700 certification?
Neither cited chamber text names UL 3700. H.5175 requires UL or equivalent NRTL certification plus outage and NEC conditions. S.3166 defines an eligible system through UL or equivalent NRTL certification and adds a 0.2-second inverter shutoff requirement. Verify the final bill and exact complete-system record; an inverter listing alone is not enough.
Would S.3166 let Massachusetts renters install balcony solar?
The Senate text proposes unreasonable-restriction and tenant-liability clauses, but those clauses are not law and use terms that differ from the defined plug-in photovoltaic system. Their scope remains unresolved in conference. Existing property law also does not replace a configuration-specific decision about a rail, facade, common area, cable route or electrical work.