Nearly Half Of US Rooftop Solar Potential Is On Low-Income Housing, Finds NREL

A new study published this week by the National Renewable Energy Laboratory in the US has found that nearly half of all the residential rooftop solar potential in the country is available atop low- to moderate-income households, representing a 320 gigawatt (GW) opportunity.

The new study from the National Renewable Energy Laboratory (NREL) was authored by Benjamin Sigrin and Meghan Mooney and looked at the divide between current rooftop solar adoption in the United States and the widening potential for further adoption. Specifically, they found that rooftop solar across the country was concentrated, not unsurprisingly, in higher-income households. However, recent cost reductions and market expansion are making way for those households not so financially well-off to begin considering rooftop solar.

Their research found that, although adoption is increasing, adoption among households considered low- to moderate-income (LMI) households — defined as those earning 80% or less of the area median income — continues to lag, prompting what Sigrin and Mooney describe as a potential “green divide.” Their research subsequently focused on determining the potential of serving these LMI households and found that there is a massive 320 GW worth of potential solar capacity atop such households. The results of their research are now available as an interactive map (found here) and will hopefully provide policymakers and industry stakeholders with the necessary information to better serve the LMI household market.

One of the key findings from the study was the fact that rooftop solar potential is substantial in most states, with high-population states like Florida, Illinois, Ohio, Pennsylvania, and Texas (among others) providing significant solar potential.

Absolute residential solar potential by county

The second key finding from the report was the realization that LMI households represent a significant portion of residential solar potential, and that single-family, owner-occupied rooftops collectively represent the biggest opportunities. As can be seen below, while these type of dwellings have a greater concentration among higher-income families, there’s nevertheless a lot of untapped potential among LMI households — nearly half, or 42% of the total annual residential solar potential, with a generating potential of 415.9 terawatt-hours (TWh).

Technical feasibility of matching residential electrical consumption with rooftop solar, by income group

The majority of low-income residential potential does not reside on single-family, owner-occupied houses, however, which means that the potential solar capacity does not conform to conventional rooftop solar models. Specifically, according to the research, the solar potential serving LMI households exist on renter-occupied and multi-family buildings rather than single-family owner-occupied buildings. In fact, if only single-family, owner-occupied roof space was used, 60% of US counties would have enough solar electricity to offset a third of LMI electricity consumption. However, if all residential building roof space was used, regardless of economic situation, 99% of counties would have sufficient potential to offset at least a third of LMI electricity consumption.

Including multi-family and renter-occupied buildings dramatically increases LMI solar potential by county. The maps show the percent of LMI electrical consumption offsettable by rooftop solar generation with single-family owner-occupied LMI buildings only (top) and with all LMI buildings (bottom).

The final finding from the research, and one that is not unsurprising given what we’ve already seen, is that if all roof space types are used for rooftop solar — single-family owner-occupied, single-family renter-occupied, multi-family owner-occupied, and multi-family renter-occupied — solar generation can then technically meet most electrical consumption for all income groups.

But being able to translate these models into reality will require smart market and policy innovation in an effort to overcome existing barriers such as credit requirements and limited access to financing, difficulties in targeting and educating low-income households, and socio-cultural perceptions of solar and solar providers.

The theory exists to provide affordable solar electricity generation to all income brackets, now governments and developers need to take the next step.