Massachusetts bill would mandate rooftop solar on new homes, commercial buildings

A new bill introduced in the Massachusetts Legislature would require that rooftop solar be included on new residential and commercial building projects.

Modeled after a similar policy in California, the bill would provide some exemptions. If the roof is too shaded, if a solar hot water system or other renewable energy technology is installed, or if the building has a green roof, it could be exempted. Affordable housing developments could also obtain exemptions.

According to the bill, amendments to the state’s building code would ensure that roofs are strong enough to support solar panels, that available roof space is maximized, and that buildings can make room for solar infrastructure. Single-family homes would need to produce enough electricity via solar each year to meet 80% of the average demand for similar houses. The state would set minimum solar energy system requirements for other buildings.

A report from an environmental advocacy group found that such a mandate would add more than 2.3 GW of solar capacity by 2045. That’s close to Massachusetts’ current total installed capacity, including utility-scale solar, of about 2.9 GW.