Plug-in solar by state › Maine
In effectLaw checked Oct 13, 2026 against P.L. 2025, c. 644 as enacted · Last change: three listing paths, net energy billing wording, liability and structure rules · Change log
Maine is the only state with a true two-tier law for plug-in solar. Up to 420 W is plug-and-play. Between 420 W and 1,200 W, a Maine-licensed electrician installs each system on its own circuit and you tell the utility. The 420 W line shapes almost every design decision.
What you can build today
No confirmed path. UL 3700: no complete system certified. Comparable standard: the component certificates need parts not on sale. NEC route: confirm the adopted code has a method with the Electricians’ Examining Board.
Always an option: a permitted, hardwired system under NEC 690 and 705 with your utility’s approval, or an off-grid power station that never connects to house wiring. UL Solutions notes the 2026 NEC “does not recognize the use of plug-in photovoltaic (PIPV) modules”; NFPA expects them in the 2029 edition (source). Where a law requires the NEC and gives no size waiver, the inspector decides. Sun Safe’s reading, not legal advice.
- Limit
- 420 W, or up to 1,200 W with an electrician
- Law
- LD 1730
- Signed
- April 6, 2026
- Effective
- July 29, 2026
What the law says
| Tier 1 | Up to 420 W AC combined inverter output per service address. No electrician required by the law. |
|---|---|
| Tier 2 | Above 420 W up to 1,200 W AC. Each system installed by a Maine-licensed electrician on a dedicated circuit with a single outlet. |
| How it’s measured | Combined inverter output, AC, per service address. Plug-in batteries count toward it. |
| Listing | One of three: listed to UL 3700; listed to a comparable standard by a national testing lab; or configured to the NEC adopted by the Electricians’ Examining Board (§ 3475(1)(A)). |
| Outage protection | Inverter set to shut off after 0.2 seconds when power is disrupted. |
| Utility notice | Tier 2 only: notify the utility within 30 days of installation on the Public Utilities Commission’s form (service address, inverter capacity, compliance statement). |
| Utility approval and fees | The utility can’t require approval, an interconnection application, agreement or study, fees, or extra equipment, and can’t deny a system that follows these rules. |
| Power sent to the grid | Not eligible for net energy billing (§ 3475(4)). |
| Utility liability | The utility isn’t liable for damage or injury from a compliant system (§ 3475(7)). |
| Not your building | Keep the structure sound, follow building, fire and zoning codes, and restore it when you remove the system (§ 3475(8)). |
In the law’s words
Short excerpts from P.L. 2025, c. 644 (LD 1730), 35-A M.R.S. § 3475, quoted as written and checked word for word against the official text on October 13, 2026; each with what it means for a plug-in design.
11 excerpts with what each means
- Tier 1
“…with a combined inverter output of up to 420 watts, measured in alternating current, per service address”
§ 3475(3)Up to 420 W AC per address. - Tier 2
“…installed by an electrician licensed in the State and uses a dedicated circuit with a single outlet … the customer complies with the notification requirement in subsection 5.”
§ 3475(3)420 to 1,200 W: licensed electrician, dedicated circuit with one outlet, notice to the utility. - Connection
“Connects to a retail customer's electrical system wiring through a standard electrical outlet”
§ 3475(1)(D)A standard electrical outlet. - Listing
“Listed or certified in accordance with UL 3700, the Outline of Investigation…”
§ 3475(1)(A)Route 1 is UL 3700: no complete system is certified yet (Oct 2026). - NEC path
“…the National Electrical Code specific to plug-in photovoltaic systems and plug-in battery systems”
§ 3475(1)(A)Route 3 is the NEC’s plug-in provisions: confirm with the Electricians’ Examining Board that the adopted code has a method. - Outage protection
“Uses inverters that are configured to shut off after 0.2 seconds if power is disrupted.”
§ 3475(1)(D)Shut off within 0.2 s of a power disruption. - Utility approval and fees
“…Pay any fee or charge to the transmission and distribution utility related to the eligible system; or … Install additional controls or equipment beyond what is integrated into the eligible system.”
§ 3475(6)No approval, interconnection application, fee or extra equipment. - Notice
“…within 30 days of installation, … a form prescribed by the commission. … may not deny the installation of an eligible system that complies”
§ 3475(5)Over 420 W: notify within 30 days on the PUC form; the utility can’t deny a compliant system. - Net energy billing
“…may not be used for net energy billing pursuant to sections 3209-A and 3209-B.”
§ 3475(4)Not eligible for net energy billing. - Not your building
“…shall ensure that the installation or operation does not compromise the integrity of the structure … shall restore the structure to its condition prior to the installation.”
§ 3475(8)Keep the structure sound and restore it on removal. - Utility liability
“…is not liable for any damage or injury caused by the installation or operation of an eligible system.”
§ 3475(7)The utility isn’t liable.
What it means for your design
- Decide your tier first. It sets your budget more than panel choice does. Tier 2 adds an electrician and a new dedicated single-outlet circuit, often more than the equipment costs.
- To stay in tier 1, the inverter’s AC output has to be 420 W or less. Two ways: an inverter rated for it (Hoymiles HiFlow Pro 420 LV or 391 LV), or a larger inverter set to 420 W in its app (the EZ1-LV allows this). If you use a setting, keep a screenshot for the file.
- The cap is on AC output, so you can put more panel on a tier-1 inverter. Two 450 W panels on an EZ1-LV set to 420 W still fit tier 1. The inverter trims the midday peak: in Sun Safe’s Rutland model that loses about 10% over a year but fills out mornings, afternoons and winter.
- Plug-in batteries count toward the same combined total. A 420 W inverter plus any plug-in battery output would push you into tier 2.
- Tier 2’s dedicated circuit is good engineering anyway: a plug-in inverter feeds current in at the outlet, and a dedicated circuit keeps that current from stacking on top of other loads on the same wire.
- Not eligible for net energy billing: size to what your home uses while the sun is up.
Designs that fit, and one that doesn’t
The engineering behind it
Why the circuit matters as much as the law, in four short points.
Circuit current, continuous output, outdoor outlets, AC vs panel watts
Why the circuit matters. A plug-in inverter pushes current into a branch circuit from the outlet end. The breaker in your panel only sees the current coming from the panel, not what the inverter adds. With other loads on the same circuit, part of the wire can carry the breaker’s full rating plus the inverter’s output without anything tripping. At 1,200 W the inverter adds 10 A at 120 V. That’s why we recommend a dedicated circuit for any plug-in system, even where the law doesn’t require one.
Continuous output. Code treats inverter output as continuous and sizes the circuit at 125% of it (NEC 705.28): 1,200 W is 10 A, times 1.25 is 12.5 A, which fits a 15 A circuit. Anything over 1,440 W needs a 20 A circuit.
Outdoors. Outdoor receptacles need GFCI protection (NEC 210.8) and an in-use weatherproof cover (NEC 406.9).
AC, not panel watts. These laws limit what the inverter puts out, not what the panels are rated for. You can put more panel on a small inverter; it trims the brightest hours and fills out the rest of the day. The Designer models that trimming hour by hour.
Questions
Is plug-in solar legal in Maine?
Yes. LD 1730 (P.L. 2025, c. 644) took effect July 29, 2026.
Do I need an electrician for plug-in solar in Maine?
Not up to 420 W AC. Above 420 W and up to 1,200 W, each system has to be installed by a Maine-licensed electrician on a dedicated circuit with a single outlet.
Do I have to tell my utility in Maine?
Only above 420 W. Then you notify the utility within 30 days of installing, on the Public Utilities Commission’s form.
Can I use a 900 W inverter in Maine without an electrician?
Only if its output is limited to 420 W. The cap is on AC output, so an inverter set to 420 W in its app stays in tier 1.