Aired Oct 20, 2026 · 26 min

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Plug-in solar, also known as balcony solar, is gaining popularity as homeowners look for affordable ways to generate their own electricity. But could this growing technology pose unexpected risks to consumers and the power grid?

Ken Boyce, Vice President of Engineering at UL Solutions, talks about the hidden safety concerns surrounding plug-in solar and what utilities need to know as adoption accelerates.

Boyce explains why none of the plug-in solar products UL tested met its new safety requirements, how these systems could create electrical shock and fire hazards, and why utilities may struggle to manage thousands of small solar installations connected to the grid without their knowledge.

With nearly 40 states having considered legislation addressing plug-in solar, the conversation explores the tension between making renewable energy more accessible and ensuring the safety and reliability of the electric grid.

Matt Chester: What happens when thousands of small solar systems connect to the grid without the utility knowing about each one? What happens when households across the country lean into this build-your-own-power system without knowing the full safety picture? Whether you call it plug-in PV, plug-in solar, or balcony solar, this trending tech is having a moment, with customers rushing to install and utilities and regulators in the position to play catch-up. Before we get too ahead of our skis, Ken Boyce, Vice President of Engineering at UL, joins us to talk all things safety and visibility when it comes to plug-in solar.

All right, so Ken, balcony solar, it's truly making solar power more accessible these days. And as a case in point, we were doing some research ahead of this episode, found a whole community on Reddit called DIY Solar. Gets tens of thousands of weekly visitors. And we came across a discussion from that community that started with the user asking, what am I missing with all the plug-in solar hype? The discussion kind of went around, hey, it requires minimal setup. It can be self-installed by the average homeowner. You're avoiding labor costs. It gives you very fast payback periods, smaller sizes, less issues about net metering, all these kind of things we've heard about. With promises like those, we can see why it's a popular technology. But I guess my question to start off with you is, what problems has the rise of this technology created for the utility sector?

Ken Boyce: Yeah, it's a really important question, Matt. I would say the promise of allowing people to participate in the energy transition and generate their own electrical power is very exciting, right? It really is great to enable people to make their own choices about how they want to generate and use electricity to a greater degree. I think the key aspect that we've been working on is to make sure it's done safely. And it can be both. It really can be both. The technology is very promising, but there are certain potential hazards that could be manifested in the use of the technology. And it's really important to be proactive in addressing those so that people get the benefits of the new opportunity to generate their own electricity, but do it in a way that will be safe.

And so the work that we've been doing really focuses on two major aspects. One is the inherent features of the plug-in PV product, photovoltaic product itself. And then the second is how that PIPV product may interact with the existing wiring system. And both of them are really important from a safety standpoint.

Matt Chester: You mentioned kind of the role you play. Can you spell that out a little bit more about what UL actually does as you're looking into these safety issues? How are you making this field safer for people?

Ken Boyce: It's what we do, right? We're a very mission-driven company. Our mission is working for a safer world. And so we're really always thinking about how do we enable these innovations to be safely and sustainably and appropriately deployed. And so our work in PIPV products has really focused on looking at those electrical and fire hazards and mechanical hazards and really thinking about what those would be in real-life use of the products and systems, and then thinking about ways that we can bring engineered solutions to mitigate those hazards from becoming real and causing an electrocution or causing a fire.

The work that we did really started last year. My team of our technical experts across a number of different technologies here, I brought them together and really asked them to do a deep dive on what the technology is today and what those potential hazards would be. That work culminated in a white paper that we published late last year that's available on our website, ul.com. And it really is trying to explain what these hazards look like in more accessible terms, right? There's obviously a very technical aspect to this, but it really is important. We wanted people who are interested in this topic to understand the results of our research, understand the findings, and really see what those potential safety hazards are.

And that work that was done on researching the products that were available in the market really led to the requirements that we published. They're called UL 3700, which are the safety requirements for these PIPV systems. And the idea there is it's a comprehensive set of construction and performance and marking requirements that really drive safe products that can be used appropriately by the public with trust and confidence that they can get the results they want, but do it in a safe way.

Matt Chester: And what's the practical output of that? You say you put out these regulations. Is it that any product sold has to meet them? Or is it just these are, you know, if you want to meet the UL standard, what does that look like in practicality?

Ken Boyce: Yeah, that's a great question. So let me go back and say the requirements that we published are really for the product certification, right? So it could bear the familiar UL in the circle mark that brings trust to millions of products that are sold throughout the marketplace constantly. That's a really important aspect for the market, right, to see that the safety has been independently verified to a very rigorous set of safety requirements. The regulatory domain is actually set by governments, right? And so they very commonly rely on that certification that we would do to say that we want to see certified products that comply with UL 3700 in this case.

And then there's obviously some other things that have to be contemplated when you're thinking about regulations for these types of products. One is, you know, does it require the electric utility to specifically permit connection to the grid, right? That's not our issue specifically that we're addressing in UL 3700, but it's a very important topic, right? So the state legislatures and other regulatory bodies have been doing work to address that particular topic. And then there's some other things about how the product would be practically used and installed that sometimes are in regulations, sometimes are in codes that are adopted more locally. And so there's this complex set of regulations at different levels and then product certifications that come together to support safe installation and use of the products in a way that is permitted in a particular jurisdiction.

Matt Chester: Yeah, that's helpful context. And I want to go back to something you said earlier, which was, you know, this PIPV or balcony solar, whichever way you want to phrase it, is giving consumers more control over their energy. But I think I guess one of the sources of tension is in giving it to the consumers. It's inherently taking it a little bit away from the power provider. Can you talk a little bit more about that tension between utility control and consumer access?

Ken Boyce: So obviously there's a lot of attention in the country right now on energy pricing, right? It's definitely something that a lot of people are thinking about. There has been a lot of activity across many states throughout the United States to think about ways to specifically allow this, right? That's driven by the legislatures and their work to look out for their constituents, right? That's really what's driving that.

I think the concept of limiting the size of the systems is one of the things that a number of the legislatures have implemented. So sometimes we see the number of 1,200 watts. So there's a somewhat limited footprint from an electrical standpoint about the potential generating capacity, but also maybe the potential impact on the grid. Obviously, there's thought about, you know, does it comply with these safety requirements? And so when you have many state legislatures, and it was nearly 40, that have either passed legislation, are working on it, or have tabled it, there is some variability in the way the different states have approached this. But we've seen a lot of common themes emerge.

And we're glad to see that there is this reliance in many of the state approaches to say the product should comply with safety requirements of UL 3700 and have that certification. That's really important because there are some very unique safety hazards associated with these products based on the way they were designed. And I'm glad to talk about that, Matt, if you'd like to hear more about it.

Matt Chester: Yeah, absolutely. We're talking about safety kind of in general term, but I'm curious about what those specific safety risks are, both for the consumer and then I'm sure for the utility and the utility workers. There's some areas there to think about.

Ken Boyce: Absolutely. Absolutely. Yeah, we definitely do try to think about safety broadly, right, as it applies to the different people that may interact with the systems. So on the consumer level, again, I mentioned there's some inherent features of the product. And one of the things that's unique to these PIPV systems is that they use a very familiar technology, a cord and plug, that we see on appliances all the time. We're very familiar with them as consumers. But PIPV systems use them in a very different way.

Traditionally, the cord and plug was used to bring power from a receptacle, an outlet that's in the building wiring system, into the appliance, into the product, so the electricity can be used to do something that we want accomplished, right? When you unplug the plug from the receptacle, the plug blades that you can touch very readily are unenergized, right? That's the nature of that connection. It's worked very well for a very long time.

The unique aspect of PIPV systems is that the PIPV system generates electricity. It's a small power plant, right? And so as long as light is shining on the PV panel, it will generate electricity. That then is converted to AC by a microinverter and is put on the plug blades. If you were to touch those plug blades, you could be exposed to an electric shock hazard. That's a really different use than what we're used to. So it looks very similar to things that we're comfortable with. It's being used in a very different way. And it does require special protective features to be introduced to make sure there's not a shock hazard to users. It's not an unsolvable engineering problem. It's just really important that it's being proven out and also proven to work in a reliable fashion, right? So we're really protecting consumers from those electric shock hazards.

There's obviously features like, you know, how effectively is it mounted? You know, we don't want it to fall off a balcony and injure someone. And these requirements associated with the inherent features of the product, we also addressed in UL 3700.

The second aspect is how do you minimize those hazards about this product being plugged into the existing wiring system? And those play out in a couple different ways, Matt. The first one is traditionally power distribution inside a building, a condo or an apartment, originates at a panel board, right? That's where the power comes in from the grid. There are overcurrent protective devices and sometimes other protective devices in that panel board that makes sure that the wiring that's being distributed through the building, the electrical connections that are being made that we can't see, but they're inside that electrical infrastructure, aren't overheating, right? So we're protecting the wires, we're protecting the electrical connections from overcurrent conditions that could cause fires or could cause shock hazards. That's worked really well. The National Electrical Code has rules that very specifically govern that and have worked wonderfully in terms of safety.

The problem is when you use a standard plug to inject additional current into that circuit, the overcurrent protective device can't see it. It's blind to it because that connection point is downstream. And so now you can overheat those wires. You can overheat electrical connections, and it could be a significant fire hazard, right? The equipment wasn't designed for that. It's not supposed to be used that way. But that standard plug configuration inherently allows you to plug those in. And you could conceivably plug multiple units in, right? And so the risk of overloading those wires and electrical connections becomes quite significant. That's a fire hazard and potentially an electrical shock hazard.

The second aspect is there are very special requirements for additional protection from electric shock for things like ground faults. And we've seen the little receptacles with the test and reset buttons. The code requires them to be placed in certain locations outdoors, within six feet of a sink. There's requirements for those devices to be placed there. And they could be either at the receptacle or they could be back on the panel board. The problem with PIPV products is that they can backfeed those protective devices, which is a misuse of those devices. But it offers the possibility that those devices may be damaged in such a way that they don't provide that protection that we're counting on anymore, and it's not apparent necessarily to the user.

And so for those reasons, it becomes a really significant safety concern, right, that someone may plug these PIPV systems in, damage that protection. The receptacle continues to provide power, but you've lost that protection. That's a really significant concern from a safety standpoint. We've really worked to break down those hazards, how they would manifest themselves, and what are some engineered features that we can use to make the PIPV systems safe, right, and not introduce those hazards. And that's what's captured in UL 3700.

Matt Chester: Yeah, that's great background. And so, yeah, obviously a lot of safety issues to consider, but also point out that we're in the Internet age. So there's always some misinformation out there or, you know, fear mongering even. So I'm curious if you've come across misconceptions or myths about what is and isn't a problem for balcony solar that you found necessary to correct along the way.

Ken Boyce: Yeah, it's a great question. And we have seen that type of misinformation. I mean, I think there's a lot of people who are dismissive of the safety concerns, saying, well, the systems don't provide that much power. It's not that big a deal. They're used in Germany, so they should be fine everywhere. And we've heard those allegations. And, you know, we're a safety company, right? We're just trying to keep people safe. That's really what we're all about. And there's a way to do it here, but we have to be clear-eyed about what those hazards are and then mitigate them, right?

And so I think we've really been spending a lot of time trying to make sure people understand that. The white paper was one step. We've definitely done a lot of outreach to the public, to regulators, to the legislatures themselves so they can understand what these issues are, and understand that there is a way to do this where we are offering these new opportunities to energy consumers, but we're also protecting them appropriately from these fire and shock and mechanical hazards.

Matt Chester: You know, a large part of our audience for the show comes from the utility sector. So I'm curious what role you think the utilities should be playing and what work they should be doing today to make sure their communities remain safe as these technologies start to take off in their jurisdictions.

Ken Boyce: There's a couple aspects of this. Obviously, we do a lot of work with grid connectivity for different technologies, right? And that really is important for the electric utilities because they're charged with maintaining the health of their grid, right? It's their responsibility to do it. And so obviously, there is an important aspect of them understanding what's being connected to the grid so that they can holistically manage the health.

You know, part of what's being done in some of these legislative actions is kind of saying, well, under certain conditions, that doesn't have to happen. That's the decision of the legislature. But obviously, the concern to the electric utility is a real one, right? A given PIPV system may not really be a significant concern. But when you start to aggregate a lot of these systems, understandably, the electric utilities have to give some real thought to how do they make sure they're keeping their grid healthy, right? That's really important. And we respect that highly with the work that we do. The PIPV legislation, though, sometimes it's, you know, permissive in ways that would be a little bit different maybe than the electric utilities would perhaps prefer.

You mentioned line workers earlier, and we do, you know, we do work on anti-islanding. That's built into what we're doing. That's built into the PIPV requirements as well. So we are thinking about making sure that a utility line worker who is charged with working on the grid when it's down isn't exposed to a shock hazard unexpectedly because PIPV is exporting, you know, and exposing them to a hazard. So that is built into what we do. You know, there's a little bit of an existential question for utilities about how will they manage this if there's a really significant uptake and the aggregate effect starts to, you know, impact the grid. It's hard work.

Matt Chester: It is. And I know it's still kind of early days, but have you seen any utilities that have approached this and made those assurances in ways that you think are really good, or they've been able to make these assets additive and not a cause of instability?

Ken Boyce: I think it's a little bit of a laboratory right now. Obviously, Utah was the first state to pass legislation. That's a place where maybe they have the longest track record of, you know, however many months of implementing this. I'm sure there are learnings there that have been relevant. California just passed its bill, so I think that's certainly a very big marketplace and the potential could be quite large to see how it's affected there with the implementation in California.

And we've definitely been in contact with the electric utilities just to really share information about what we have done, which is really primarily focused on protecting the consumers, you know, on the consumer side of the meter. But we want to share that information so that we have the right discussions happening about the best possible way to do this and get the right results for the grid, for the public, for society. And they all matter.

Matt Chester: Yeah, absolutely they do. And yeah, so we're talking about the utility side. Now I'm curious about that consumer side. As they're going out and shopping for these PIPV technologies, what do you think they need to be aware of, maybe beyond just looking for that UL logo that we talked about earlier?

Ken Boyce: We always say that's one easy way to know that it's okay. Look for the UL mark. I think the key that we've really tried to focus on as we talk about this is there are products that are available in the marketplace today that we acquired for our research program when we were doing that initial research last year. And I will tell you that we haven't tested every product that's available on the market. None of the products that we did test actually would comply with those requirements for UL 3700 for safety.

And so making sure that there is attention to protecting yourself and your family from those risks that may not be readily apparent, but they're very real, is a really important message. And again, we're trying to work for a safer world. So we've really, really tried to focus on that message. Look for a certified product, right? That would give you the trust that would make you feel good about bringing that product into your home.

Matt Chester: Again, it's early, but things are moving fast. And, you know, it's interesting to hear all the background work you're doing here. So I'm curious if you have to look ahead, even just a year from now, where do you see this whole PIPV conversation sitting at that point?

Ken Boyce: There are a couple important things happening. So I think we're evaluating products to UL 3700. We don't have any certifications yet, but we should soon. And that will be a really important milestone. So I think the work is going on in the industry to get those certifications. And then that would really bring a level of trust that just isn't there today. That's important.

I think there's another important set of work underway in the National Electrical Code. The present edition of the NEC doesn't specifically address these PIPV-type products. There's specific requirements for rooftop solar. There's specific requirements for, you know, solar plants that are privately owned. There are requirements that maybe are peppered through the code that would be relevant when you think about this. But there's not a very clear set of requirements for PIPV. That actually is being addressed right now. So just in the last several weeks, the first meeting of the committees that will develop the next edition of the NEC are working on this exact topic. And so there is a lot of work ahead in that process. It'll play out over the next year and a half.

But so far, you know, there is good recognition that there are some safety concerns here. We do need to have more specific rules in place for how to install these, and the committees are working on that. So I think that also would bring a level of clarity and be important for just making sure people understand the rules about what is okay and what's not. And then we'll see the state legislatures continue to move their work forward or even refine some of the work that they perhaps have done as some of these other really important market-facing aspects click into place.

And so I think we'll see a lot of activity, a very dynamic market implementation for the next year to year and a half. But then I feel like we'll be in a very good place to have clarity around what you can do and what you should not do. We're confident that the work we've done will continue to enable those decisions to be made at all levels from a government down to a consumer. But it's really important that people are mindful of keeping themselves and their loved ones safe because it's very important here.

Matt Chester: Absolutely. There's nothing more important than that when you put it that way. So, Ken, I want to end on kind of a bigger picture here. You know, I saw a story recently about UL also taking up vehicle-to-grid technology. So between things like PIPV and V2G, can you speak a little bit to how UL determines which of these emerging tools are ready for primetime and how you get involved in making sure it's not in a way that's maybe a roadblock to innovation, but, you know, really just making sure it's being done the right way?

Ken Boyce: That is such an insightful question because we really do pride ourselves on understanding what's happening in the marketplace, what are these emerging trends, and then being proactive in having those requirements in place at the right time. And so sometimes it's because one or more manufacturers come to us and they say, hey, I have this great new idea. Sometimes in the case of V2G, you know, we just see what has happened. And that actually goes back to the aftermath of the Fukushima event in Japan, right, where people started doing that out of necessity. And then it kind of got a foothold, right? Hey, we can use the technology to do this.

So we've been working on that for a number of years through a number of different iterations. This most recent iteration was really focused on driving clarity between the requirements in our grid connectivity standard, UL 1741, and that's relied on very heavily by the electric utilities and the utility commissions to say, here are requirements. Your regulation references UL 1741. Here's requirements that address that. And you don't have to change your regulation. It's in UL 1741.

I think those types of things will certainly continue to happen, this energy transition with distributed energy resources and increased connectivity and this intricate, sophisticated web of energy assets that work together in ways that could never have happened before. We'll certainly continue, and we'll certainly continue our work to be ready with safety science to make sure that can happen safely.

Matt Chester: Amazing. Well, that's very well said, Ken. And this has been a compelling conversation in really a rapidly growing area. So we appreciate you giving us the lowdown and thank you so much for joining us today.

Ken Boyce: Thank you for having me. It's been a great discussion, Matt.

Matt Chester: Of course. And thanks as always as well to our Energy Central community, our viewers, our listeners for joining us today. We'll see you again on the next episode of Power Perspectives.