BOSTON -- The solar industry says uncertainty around clean energy incentives is bad for business, and is asking Gov. Charlie Baker to take action.

A coalition of solar groups wrote Thursday to Matt Beaton, Baker's energy secretary, asking that the SMART program -- a solar development incentive under review for months -- be launched as soon as possible.

The state Legislature authorized the program in 2016; final regulations were filed a year ago, but SMART has yet to be implemented by the Massachusetts Department of Public Utilities.

"As a result, the solar industry is slowing down and shedding jobs," reads the letter from the Coalition for Community Solar Access; MassSolar; the Northeast Clean Energy Council; the Solar Energy Business Association of New England; the Solar Energy Industries Association; and Vote Solar.

SMART, which stands for Solar Massachusetts Renewable Target, is designed to bring 1,600 megawatts of new solar online. The tariff-based incentive was created to replace the market-based solar renewable energy credits. Previously, it was expected that SMART would be available sometime over the summer.

"Without clarity on the final SMART rules, firms are unable to close deals with lenders and entire portfolios of projects are at risk," the industry groups said.

The letter said statewide solar installations in the second quarter of 2018 were only a third of what they were in 2017. It said the stalled SMART incentives, combined with immovable net metering caps, are to blame.

"As a result, the solar industry is slowing down and shedding jobs," the groups said.

The Republican has reached out to the Baker administration for comment.