All Solar Big and Small: Plug-In Solar is Coming to New Hampshire
- Clean Energy NH
- 1 day ago
- 6 min read
The future of solar PV in New Hampshire is brighter as New Hampshire’s Governor signs Senate Bill 540 (SB540) into law making access to solar almost as easy as plugging in a toaster.
This summer, New Hampshire became one of the first states in the nation to create a clear legal pathway for safe deployment of plug-in solar. SB540, signed into law by Governor Kelly Ayotte on July 2nd, allows Granite Staters to install small solar systems up to 1.2 kW that plug directly into a qualified wall outlet bypassing the need for rooftops, permits, and significant upfront investment. This legislation creates a viable pathway for renters, apartment dwellers, and budget-conscious households to access solar easily. Critically, the New Hampshire bill does so with safety built in from the start: pairing expanded consumer access with mandatory safety requirements and a deliberate timeline that lets national standards be completed to ensure New Hampshire plugin solar provides affordable, safe generation. One important caveat for consumers: the kits being marketed online today are not yet certified under the safety standards New Hampshire's law anticipates, as we explain below.
Plug-in solar has become one of the most successful clean energy projects in Europe. In Germany, an estimated 4 million households now use small, portable, “balcony” solar panels that plug directly into a wall outlet. No electrician, permit, or rooftop required; just pick up a system at the local Lidl or Aldi, and assemble it yourself, Ikea style. Adoption of these systems grew roughly 73 percent in 2024 alone, and it’s not hard to see why: these portable systems cost a fraction of traditional rooftop arrays and are available to a broad range of households who have been unable to invest in rooftop solar installations. If this model takes hold in the United States, it could do something that rooftop solar has been unable to do: make solar ownership accessible to households who never thought it possible to utilize solar power to lower their bills.
SB540's increases the financial accessibility by stripping away the costs that typically stand between a household and solar ownership. Under the new law, compliant plug-in solar systems are exempt from the requirements that drive up the price of traditional installations: no utility approval, no interconnection review or agreements, no additional utility-mandated equipment, and no associated fees. Because these systems plug into a qualified wall outlet and are installed according to manufacturer instructions, the households also avoid the labor and permitting costs of a professional rooftop installation. The result is a solar option whose total cost is a fraction of a conventional rooftop array, putting ownership within reach of households for whom the upfront investment has always been the biggest barrier.
But American homes are wired differently, and this distinction matters.
Unfortunately, it’s a mistake to think plug-in solar in the US will roll out as simply as Germany’s model. Residential electrical systems, codes, and safety requirements in the US were built around the assumption that power only flows from the grid into the home. Plug-in solar breaks that assumption by feeding power back into the household circuit through an ordinary wall outlet, creating complex engineering questions that must be answered to ensure household safety.
A 2025 UL Solutions white paper laid these concerns out plainly. Standard branch circuit breakers are sized to catch overloads from the grid side only. In effect, these circuit breakers can't "see" a solar inverter also feeding electric current into the same circuit. This means if the circuit could, theoretically receive current from the plug-in panels as well as from the grid at the same time, leading to a combined overload that overheats the circuit. The same two-sided loading can occur in Germany, but in the European Union homes are wired at 220 volts instead of 120, which means EU wires and circuits can safely accommodate larger loads than in the US.
The electric plug from the solar panels themselves is a concern, too. For a typical appliance, the prongs of a plug are safe to touch the instant it's unplugged from the wall socket. However, the UL's testing found today's grid-interactive inverters may continue to energize the prongs of a plug for up to two seconds after the plug is disconnected from the wall socket as there is a delay before the inverter registers it is no longer feeding into the building’s wiring. Further, UL found that plugging a solar device into a Ground Fault Circuit Interrupter (GFCI) protected outlet, the same protection required near sinks, pools, and outdoor receptacles, could in some cases damage the GFCI or let current keep flowing into a ground fault for a moment after it trips.
Neither of the above issues means that plug-in solar is unsafe, but rather points to the fact that the technology must be adapted to US standards for building electrical systems first rather than treating these smaller solar arrays like any other plug-in appliance you buy off the shelf.
Fortunately, the global enthusiasm for plug-in solar means that smart folks across the US are turning their attention to these problems. UL Solutions, the same organization behind the safety testing for nearly every appliance in your home, is developing a dedicated standard for this technology. The UL 3700, the Outline of Investigation for Interactive Plug-In PV (PIPV) Equipment and Systems, is designed to address the specific gaps identified above: touch-safe output circuits, compatible GFCI protection, and overcurrent protection tailored to the connection these devices have to your home. This is exactly the kind of independent, rigorous safety procedures that should underpin any new class of consumer electrical product, and it's why we believe the technology's promise and the need for caution aren't in conflict, they're two sides of the same process.
In the meantime, buyers should be careful. Plug-in solar kits are already being marketed and shipped nationwide, including to New Hampshire — some at attractive prices and with confident safety claims. But until UL 3700 is finalized, no product on the market has been independently certified against the specific risks described above, and the updates to New Hampshire's building code and interconnection rules that will define a qualifying system under SB540 have not yet been made. A manufacturer's own safety reasoning, however thoughtful, is not a substitute for independent certification — that's the entire reason the UL process exists. Our advice: be patient, be skeptical of "available now" marketing, and wait for certified products and consumer guidance from the NH Department of Energy before plugging anything in.
New Hampshire has an opportunity to get this right from day one.
SB540 builds safety requirements directly into the bill: automatic shutoff during a power outage to protect line workers, mandatory compliance with the state's existing fire and electrical codes, and installation according to manufacturer instructions. The bill drew engagement not just from clean energy advocates but from the utilities and the state’s building inspectors and code officials, who are responsible for enforcing these rules on the ground.
The law was written to allow for the regulations to catch up with the technology, before plug-in solar starts to roll out across our state. Specifically, the law makes it clear that necessary changes to the building code and interconnection rules won’t occur until the UL 3700 standard has been completed, and we can be sure that compliant devices are being manufactured.
New Hampshire doesn’t have to choose between opening solar access and protecting public safety. SB540 shows that these goals can reinforce each other: a technology with the ability to expand energy affordability, paired with a deliberate, forward-thinking legislative process and an evolving national safety standard built to ensure success. SB540 represents the best of how policymaking can be done well at the State House: bipartisan legislation that expands consumer choice while taking safety seriously from the very beginning. By pairing innovation with rigorous safety standards and clear regulations, New Hampshire has created a blueprint that other states can follow.
It’s worth noting that SB540 complements Senate Bill 538 (SB538), which Governor Ayotte signed into law on July 10, 2026. SB538 provides critical support for New Hampshire municipal solar projects up to 5 MWs in size. This bill guarantees the current net energy metering (NEM) credit for 20 years for cities, towns, school systems, and counties with projects already in the interconnection queue. This guarantee will enable those projects to receive better financing terms for large solar projects across the state, providing taxpayer relief by reducing government energy costs. By signing both SB540 and SB538, the Governor increased the opportunity for even more Granite Staters to realize the economic benefits of local, renewable, clean electric generation.
**For additional context, read the article published by PluginSolarUS.com's "Behind the Bill" series. The article is based on an interview with New Hampshire Sen. David Watters and Sam Evans-Brown of Clean Energy NH, public legislative materials for SB540, and additional background research.