Chapter 7C of the General Laws is hereby amended by inserting after section 29 the following section:-

Section 29A. (a) As used in this section the following words shall have the following meanings unless the context clearly requires otherwise:-

“Effective solar area,” the portion of a building roof on which the output from a solar energy system, taking into account shading from existing permanent natural or manmade barriers external to the building (including but not limited to trees, hills, and adjacent structures), would be equivalent to 70 percent or greater of the output of an unshaded solar energy system on an annual basis.

“Solar energy system”, any system that uses solar energy to provide all or a portion of the electrical needs of a building.

“Substitute renewable energy system”, any system that uses renewable energy resources other than solar energy to provide for all or a portion of the electrical needs of a building; provided, that a renewable energy system shall use a technology eligible for the renewable portfolio standard under subsection (c) of section 11F of chapter 25A of the General Laws.

(b) Beginning on January 1, 2020, the commissioner shall require a state agency that initiates the construction of a new facility owned or operated by the commonwealth or a renovation of an existing facility owned or operated by the commonwealth when the renovation costs exceed $25,000 and includes the replacement of systems, components or other building elements which affect energy consumption to install a solar energy system on or near the facility.

(c) If the effective solar area is sufficiently large, the solar energy system shall produce enough electricity on an annual basis to meet 100 percent of the projected annual electricity demand of the building.

(d) If the effective solar area is insufficient to meet 100 percent of the building’s projected annual electricity demand, the state agency shall either (1) install a solar energy system occupying as much of the effective solar area as possible, or (2) install a ground-mounted solar energy system, provided that the installation of a ground-mounted solar energy system does not cause an unacceptable negative impact to the commonwealth’s natural or historic resources, and provided that the solar energy system shall be sized to meet 100 percent of the building’s projected annual electricity demand or the maximum possible given the available space.

(e) An agency may seek an exemption from the requirements of this section if the effective solar area is less than 80 contiguous square feet and there is no suitable location for a ground-mounted solar energy system.

(f) An agency may seek an exemption from the requirements of this section if a substitute renewable energy system will be installed at the time of construction meeting 100 percent of the building’s projected annual electricity demand, or producing an equivalent amount of electricity on an annual basis as the largest solar energy facility possible under subsection (d) of this section. An agency may seek a reduction in the required size of a solar energy system upon a sufficient showing that a substitute renewable energy system will be installed at the time of construction, producing sufficient electricity on an annual basis to offset the reduction in electricity produced by the solar energy system.