May 8th, 2026
Via MIT Technology Review, a look at the growing popularity of plug-in panels:
Dozens of US states are considering legislation to allow people to install plug-in solar systems, often called balcony solar. These small arrays require little to no setup and could help cut emissions and power bills.
Balcony solar is already popular in Europe, and proponents say that the systems could make solar power more accessible for more people in the US, including renters. As popularity rises, though, some experts caution that there are safety concerns with how balcony solar would work with existing electrical equipment in homes.
Let’s talk about what balcony solar is, why it’s unique, and how new testing requirements could affect our progress toward deploying the technology in the US.
Plug-in solar systems are designed to be simple to install, often requiring no electrician or specialized worker at all. They’re small, and many can be plugged into existing outlets.
People across Germany have installed over a million balcony solar systems. They generally measure up to roughly two square meters or about 20 square feet, and can generate up to 800 watts—enough to power a standard microwave.
Now the plug-in solar wave is coming to the US. Many Americans have already installed DIY balcony solar without the permission of their utilities—it’s something of a regulatory gray area. In late 2025, Utah became the first state to explicitly allow people to install and use balcony solar systems. Over two dozen other states are now considering similar legislation.
Generally, utilities require users to sign an interconnection agreement before they can plug in large arrays of solar panels that generate power for the grid. There can be fees and permits, and it all amounts to an expensive and lengthy process.
Utah’s law ditched the interconnection requirement for panels that have a low power cap and that are certified by a national testing facility. (Legislation under consideration in other states, including New York, includes the same requirements.) The thinking is that since the panels produce very little power, which would be used to meet a home’s own energy demand and probably not get sent back to the grid, the same requirements shouldn’t apply.
As for that certification piece, in January the national testing and certification lab UL Solutions released UL 3700, a testing protocol to certify balcony solar systems and ensure that they’re safe.
There are three main safety considerations to address for these plug-in solar systems, says Joseph Bablo, manager of principal engineering, energy, and industrial automation at UL Solutions. First, there’s the possibility of overloading a circuit. Generally, electrical circuits have circuit breakers, which can trip and interrupt current if necessary. But if there’s a solar panel adding extra power to a circuit, a traditional breaker might not be able to respond to overload. Over time, overloaded circuits can damage equipment or even start a fire.
Second, these small systems are typically installed on the outside of homes, and outdoor power outlets generally have ground fault circuit interruption (GFCI). Basically, if an outlet or its surroundings are wet, it can shut down to prevent electric shock. Many GFCI systems may not work if there’s power going back into an outlet from a solar panel.
Finally, there’s touch safety: If a plug gets disconnected from the wall, the blades of the plug may still have power running through them for a short time. If a panel is getting sunlight, those blades could be energized for longer than is typical.
The new UL Solutions testing framework aims to address these concerns. One of the key recommendations is that plug-in solar panels should use a special outlet that’s designed specifically for them. The safety measures included in that connection, and within a panel, would ensure that the panels are safe.
The need for a special outlet means that currently, people who want to plug in a solar panel array would probably need to have an electrician come and update their wiring in order to comply with the protocol, Bablo says. “I know they want to say ‘No electrician, no permits’—we’re not there.”
Today, anyone can buy products like solar panels and inverters, some of which carry their own component UL certifications, and string them together. (Inverters are covered under UL 1741, for example.)
But the gold standard is to have an entire system that meets the safety requirements, and that means adhering to the new standard, Bablo says. As of early May, there aren’t any plug-in solar systems that have been fully certified by UL Solutions. And Bablo said he couldn’t share information about what, if any, are in the pipeline.
Even with the new certification requirements, Bablo still thinks plug-in solar still has the potential to help more people access the technology. “There’s a way for it to work, but we want it to work safely,” he says.
'Black Swans' are highly improbable events that come as a surprise, have major disruptive effects, and that are often rationalized after the fact as if they had been predictable to begin with. In our rapidly warming world, such events are occurring ever more frequently and include wildfires, floods, extreme heat, and drought.
'Green Shoots' is a term used to describe signs of economic recovery or positive data during a downturn. It references a period of growth and recovery, when plants start to show signs of health and life, and, therefore, has been employed as a metaphor for a recovering economy.
It is my hope that Black Swans / Green Shoots will help readers understand both climate-activated risk and opportunity so that you may invest in, advise, or lead organizations in the context of increasing pressures of global urbanization, resource scarcity, and perils relating to climate change. I believe that the tools of business and finance can help individuals, businesses, and global society make informed choices about who and what to protect, and I hope that this blog provides some insight into the policy and private sector tools used to assess investments in resilient reinforcement, response, or recovery.