Lawmakers are voicing concerns with state regulators about a potential 60 percent reduction in the value of credits available to residential customers in connection with community solar projects.

In a letter Monday to Department of Public Utilities commissioners Angela O’Connor, Cecile Fraser and Robert Hayden, 16 senators and 63 state representatives said elements of a solar energy program pending for approval before the agency could thwart the growth of the solar industry and “limit access to solar for millions of renters, low-income residents, and other ratepayers for whom rooftop solar is not an option.”

Lawmakers support the overall design of the new Solar Massachusetts Renewable Energy Target Program (SMART) but oppose a “harmful cap” on customer credits within an alternative on-bill credit mechanism proposed by utilities. The cap threatens to undercut the goals of a 2016 solar energy law, according to the lawmakers, a group that includes Sen. Jamie Eldridge and Rep. Frank Smizik.