Two communities separated by little more than a municipal boundary can experience the economics of rooftop solar very differently, even when they share the same weather, electric utility and many of the same incentives.
That is the finding of a new study, published in Renewable Energy, from NYU Tandon researchers Anton Rozhkov and Shenghan Lyu, who compared rooftop solar in Chicago’s Austin neighborhood with neighboring Village of Oak Park, Illinois. Their analysis suggests that policies designed to make solar affordable can produce sharply unequal benefits depending on who owns the buildings, how much money residents have and even the size and shape of their roofs.
For Rozhkov, the comparison offered something close to a natural experiment. Oak Park and Austin sit directly beside one another, divided by only a narrow street, and share the same utility and basic infrastructure. But socially and physically, they are quite different. Oak Park is wealthier and has more homeowners, while Austin has lower household incomes and a larger share of renters.
The researchers wanted to know whether a largely uniform set of solar incentives would work equally well in such different places. To find out, they combined detailed electricity-use records with high-resolution aerial imagery. Using Geographic Information System (GIS), researchers manually mapped rooftop solar installations and measured available roof space, then fed those data into a financial model estimating the value of solar projects over 20 years. The model incorporated existing federal, state and local programs, including the federal Investment Tax Credit, Illinois renewable-energy incentives and an Oak Park grant program.
The maps revealed an immediate contrast. Less than one percent of rooftop area in either community was covered by solar panels. But roughly two thirds of Oak Park’s installed solar area was residential, whereas more than 84 percent of Austin’s was on commercial buildings.
That matters because many solar incentives scale with the price and size of an installation. The federal tax credit, for example, reduces costs by a percentage. A large commercial roof can therefore capture a much larger absolute benefit than a small residential system. Local lump-sum grants help households, the researchers found, but do relatively little to change that underlying advantage of scale.
The researchers also uncovered a more subtle divide among households. Low-income residents can qualify for programs that substantially reduce upfront costs, but sometimes they lack knowledge about the availability of those benefits, while affluent homeowners may have enough capital to install panels without relying heavily on subsidies. Households in the middle can fall between those two groups.
“They’re falling into this policy gap,” Rozhkov said. “They’re not low-income, so they’re not getting this assistance. At the same time, they’re not that wealthy that they can just go and purchase solar panels.”
Upfront cost proved especially important for lower-income households. A sensitivity analysis found that capital expenditure accounted for about 66 percent of the variation in their projected financial outcomes. For wealthier households, electricity-price changes and financing conditions became increasingly important instead.
Perhaps the study’s most striking result was the mismatch between theoretical profitability and actual adoption. Under current incentives, the researchers’ model pushed most residential solar projects into positive financial territory. Yet real-world rooftop adoption in both communities remained below one percent. The implication is that making solar profitable on paper is not enough. Renters may have little authority to alter their roofs, landlords may have weak incentives to invest, and homeowners may face roof repairs, electrical upgrades or financing hurdles before a panel can ever be installed.
That points toward a more targeted approach to distributed-energy policy and infrastructure planning. Assistance with roof repairs, electrical upgrades, low-cost financing and community solar could address barriers that a broad tax credit cannot. Middle-income households may need their own tier of support rather than being left between programs aimed at lower-income residents and incentives that work best for people who already have capital.
For Rozhkov, the study is part of a broader effort to understand how cities can transition toward more decentralized energy systems. His research examines how rooftop solar, microgrids, energy storage and demand management interact with urban form, infrastructure and public policy, and how those systems can be planned to improve affordability and resilience across different communities. As Rozhkov put it, the question is not simply whether solar incentives exist. It is whether different communities can actually use them.
