Jenny Blair
For many Vermonters, a rooftop or backyard solar array is out of reach. For renters, these systems don’t make sense. And many homeowners balk at the cost, even with financial incentives. In any case, residential rooftop solar tax credits are expiring at year’s end thanks to changes in federal law.
But small, cheap, ready-to-go “plug-in solar” could be another option. Also called balcony, backyard, or portable solar, it consists of one or a few solar panels that can be plunked on a balcony, hung outside a window, or propped on the ground to generate electricity. Through a device called an inverter, which converts direct current to alternating current, this electricity can be plugged into a battery, a household wall outlet, or both. No electrician is needed for the install.
The result can be lower household electric bills, reduced greenhouse gases, and less strain on aging electrical grids.
“These units can offset about a fifth, in most cases, of household consumption at the 800 to 1200 watt threshold,” said Cora Stryker, co-founder of the California-based plug-in solar nonprofit BrightSaver. “They’re accessible to a huge group of people who want solar but can’t get rooftop or community solar.”
“It does seem like portable solar has a lot of potential for Vermonters, especially for equity purposes, especially for renters, to have access to solar to potentially lower their bills,” said state Sen. Anne Watson (D/P, Washington District). “I think it’s worth looking into.”
Plug-in solar currently occupies a regulatory gray area in the United States. But it is starting to attract attention. Recent changes to German law have led plug-in solar to become hugely popular there. Major media outlets have recently covered the technology and its adoption here and abroad.
In March, Utah lawmakers became the first in the U.S. to pass a law explicitly removing key hurdles to plug-in solar. Could Vermont be next?
Safety, Costs, and Laws
A well-designed plug-in solar array’s inverter shuts off instantly if the hardware detects that the grid has gone down. This “anti-islanding” feature is also present in conventional solar arrays and is key for protecting line workers.
Safety data in Germany have been reassuring so far, according to an Aug. 12 article in the Washington Post.
As for costs, the present per-watt costs of plug-in solar are about on par with rooftop arrays, according to Stryker. But startup costs and the payoff period are much lower, making for a good return on investment even without subsidies, she said.
The nonprofit recently sold out of its 200-watt units (at $399 each), which pay for themselves in about five years.
In Germany, typical units generate 800 watts, according to an Aug. 12 article in The New York Times. Costs have dropped there and people can recoup their investment in two years or less, according to Stryker.
Utah’s new law allows up to 1.2 kilowatts, or 1200 watts, of solar power from portable units to be plugged straight into the wall. Users don’t have to enter an interconnection agreement with local utilities to send small amounts of electricity to the grid.
The law was popular on both sides of the aisle. Introduced by Republican Rep. Raymond Ward, it passed Utah’s House and Senate with zero no votes and a few abstentions before the state’s Republican governor, Spencer Cox, signed it into law.
“Essentially, there are no fiscal implications, no money allocated at all to this. It’s just changing one small part of a one-size-fits-all regulation,” Stryker said.
Utah requires that the units meet National Electrical Code and Underwriters Laboratories (UL) standards, according to a March 5 article in pv magazine, which covers the photovoltaics industry. Underwriters Laboratories has not yet issued such a safety standard for plug-in solar systems, though individual components do have such standards.
The lack of updated regulations, safety standards, and approvals are major obstacles to widespread U.S. uptake, an April 25 Grist magazine article concluded. According to Grist, the United States today is about where Germany was a decade ago in this regard.
The Future of the Current
In Vermont, plug-in solar appears to be an awkward fit with current state and municipal regulatory frameworks. Multiple state and local officials as well as power company representatives told The Bridge they were either unfamiliar with, looking into, or interested in learning about the technology.
Stryker believes the twin benefits of affordability and clean energy will help make the case for plug-in solar.
“We have to hit that threshold where it’s not just people who can pay a green premium for green solutions, [but] it’s actually a money-saving thing in addition to a planet-saving thing,” she said.
Currently, BrightSaver is discussing plug-in solar with stakeholders around North America, she said, including in Vermont, where, she said, “there’s a real focus on climate from the utilities, and a real concern about clean energy that actually makes us super excited.” (She declined to say with whom she is speaking.)
“If we do this right, the market comes in and they take care of it. We don’t have to constantly be lobbying for subsidies,” Stryker said. “It’s like the carrot [and] the stick. We don’t need carrots to make this take off. We just need to release the restrictions.”
