Plug-in solar, also known as balcony or backyard solar, refers to a solar system that plugs into a standard 120V outlet in your home or apartment. A plug-in solar system can be installed on the ground (in a backyard), alongside a fence or building, outside a window, or on a deck or balcony. Unlike a standard rooftop system, the system does not usually have to be professionally installed and is smaller in size. A plug-in solar system can be up to 1,200 watts (W), 1.2 kilowatts (kW), while a standard rooftop system typically ranges from 7 to 15 kW.

Plug-in solar is a more equitable and affordable option for those who would like to use clean energy and save money but cannot access rooftop solar, whether it be because they cannot afford to own or lease a full system, do not have the proper roof capacity, or do not own the property in which they live.

The energy generated by the solar system goes directly into the household wiring, allowing other appliances to take from that energy. Because the home uses power from the plug-in solar system first, it draws less electricity from the grid, which lowers the household's electric bill.

A plug-in battery system can be combined with the solar system to fully utilize the generated energy. Plug-in solar systems do not qualify for net metering, so there is no way to use or be compensated for excess generation at this time. The best way to fully utilize the generated energy is by combining the system with a battery.

For example, if someone installs an 800 W system, but does not have the energy consumption during peak solar generation hours to use that energy (e.g. they work in-person), they lose out on that energy. If they had a battery system, that excess energy could be stored and used when their consumption increases, such as when they return home. Combining the two technologies together would provide the most benefits and increase resiliency.

As an emerging technology in the United States, safety is at the forefront of plug-in solar. Safety professionals have established a 391 W threshold for plug-in solar systems that can simply be plugged in without modifications to a building’s existing wiring, a limit that has been incorporated into legislation in several states, including Massachusetts. For more information, check out the statement that Bright Saver has worked on in collaboration with Brooks Engineering and Permit Power about the safety. Consumers that purchase a certified plug-in solar system should follow the manufacturer’s installation instructions.

Plug-in solar systems are also designed with built-in microinverters that automatically shut the system down within milliseconds of a power outage, helping protect both consumers and utility line workers from electrical hazards. In addition, state plug-in solar laws required systems to be certified by a nationally recognized testing laboratory (NRTL), the same type of certification process used for many common household electrical products.

Plug-in solar is not currently illegal. It is, however, subject to the same requirements as rooftop solar despite their differences in size and capabilities. These requirements create unnecessary barriers to plug-in solar, which is intended to be a more accessible pathway to solar, as these systems are significantly smaller than the standard rooftop solar installations that require these procedures.

Plug-in solar legislation removes unnecessary requirements like interconnection agreements. Bills have been passed and developed in several states, including Massachusetts, and they address four main points: defining a plug-in solar system, establishing basic safety requirements, exempting plug-in systems from net metering and interconnection requirements, and prohibiting any fees or additional equipment requirements for a plug-in solar system. Some additional provisions in the Massachusetts legislation include an exemption from professional electrical work and installation for smaller systems (e.g. 391 W exemption) and language around tenant rights, making it so that landlords cannot prohibit the installation of a plug-in system. The legislation ensures that plug-in solar is accessible, not subject to unnecessary requirements, and provides necessary clarity for consumers and public entities alike.

Prior to the legislation passing, the availability of plug-in solar systems was limited. However, we anticipate that the market will develop and that several models will soon become available as a result of the legislation.

Here at Green Energy Consumers Alliance, we are committed to educating consumers and expanding access to clean energy technologies. We are working on a pilot project funded by the Massachusetts Clean Energy Center with Bright Saver and Boston Housing Authority to distribute plug-in solar systems to low- and moderate-income (LMI) Boston residents, as well as two demonstration sites at community centers in Boston. Bright Saver is a national non-governmental organization focused on pioneering the deployment of affordable plug-in solar, and Boston Housing Authority a housing provider in Boston with a civic mission to provide quality affordable housing to thousands of LMI households.

Beyond this initial pilot, we intend to educate consumers about plug-in solar options, and launch a group buy program for interested consumers in Massachusetts, and eventually Rhode Island once legislation passes there as well (we’re working on it!). If you are interested in staying up to date on plug-in solar developments or participating in a group buy program, please fill out our interest form!