Research at Weitzman: Sanya Carley on Residential Solar

From mitigating climate change to protecting cultural heritage and combatting social inequality, Weitzman faculty members are engaged with the most pressing issues in the built environment that we face today. Research at Weitzman tracks developments in the lab and in the field.

Are households with residential solar panels more likely to keep up with all of their energy bills and to live in comfort? Sanya Carley, the Mark Alan Hughes Faculty Director of the Kleinman Center and Presidential Distinguished Professor of Energy Policy and City Planning, researches the factors that affect household energy security. With a team of colleagues at the University of Pennsylvania and Indiana University, Carley runs the Energy Justice Lab and hosts a web tool with up-to-date data on utility disconnections. Carley is currently completing a research project on the impact of residential solar electricity on household energy security and thermal comfort. The work, in collaboration with Indiana University and the Lawrence Berkeley National Laboratory, is under review.
 

What’s the primary audience for this research? Who would be interested in reading it?

I think our primary audience is threefold in this case. One is other academics. It’s really important to build the literature and the knowledge and understanding of the issue of potential solutions for energy insecurity. And then our external audiences include policymakers who are working on addressing the problem of energy insecurity as well as practitioners who are on the ground deploying solar.

How does it add to their understanding of the issue?

We’ve been studying energy insecurity for quite a while now and one of the leading indicators that we’ve found of households becoming energy insecure is that they were energy insecure previously. For example, if a household is disconnected, it is very likely that the household was disconnected previously. This has led us to ask questions like, “How do we prevent households from ever entering this state or this cycle of energy insecurity?” The Energy Justice Lab has been thinking really hard about different preventative solutions. One kind of preventative solution is weatherization. Let’s seal up the homes, make them less drafty and more efficient, and reduce energy bills in the process. In our solar project we ask: Can a household access small-scale residential energy technologies that also bring down their energy bill and thereby help them avoid energy insecurity? We’ve come at this from a preventative-solutions approach.

How could small-scale residential solar have an effect on energy insecurity?

It could go through a few different mechanisms. The most important and logical is that solar would just bring down a household’s energy bills. When households have their own solar panels, they can use some of that electricity to offset what they would pay their electricity provider, and thereby they would lower their energy bills. The other mechanism is a little fuzzier and harder to test, but it’s providing autonomy to a household-- energy autonomy, that is. Residential solar could essentially sever the link of dependence between a household and a utility provider. We theorize that having that degree of autonomy would help a household be more in control of their energy consumption and their energy bills and help them become less energy insecure.

Why now? What’s the timeliness of this project?

Data has gotten so much better and more detailed, which can help us understand the challenges of energy insecurity. There is also a phenomenal wealth of solar data that exists nowadays where we can identify every single household in the US that has put up residential solar. That’s part of it. The other part of the timeliness is the pervasiveness of energy insecurity. It’s a growing problem that’s getting worse every year as energy bills continue to rise across the United States.

What are the hardest aspects of the research, and what are the most rewarding or surprising parts of it so far?

The hardest part is from an empirical, causal-inference perspective. We cannot randomly assign households to adopt solar or not. We instead have a database of all households that have adopted solar. They’ve essentially already selected themselves into treatment, which makes a robust causal inference very difficult to do.

What we did, however, was we took this database of all these households, we ensured that we were looking at just low-income households in particular, and then we matched all the solar households with households that don’t have solar on a whole series of observable characteristics. That includes the size of the house, the location, the climate zone, the number of residents in the house, the racial makeup of the house, and the income of the house. Essentially we’ve created this sample that matches the solar sample as best as we can. But it’s still a limitation in that this study does not have a perfect counter-factual, and it is entirely focused on the post-adoption period.

It’s rewarding in two ways. One is just the collaboration with the national lab and Indiana University—It’s a fabulous collaboration of really smart people. The other particularly rewarding part is to move the needle on our understanding of preventative solutions to energy insecurity.

Anything you would like to add?

Some people have said that this should be really obvious: of course solar reduces energy insecurity. But nobody’s studied this before. And practitioners really need this kind of evidence—true evidence that they can use to figure out how to better target households that really need support.