Before entering into a guaranteed energy savings contract under Section 15, a unit of local government shall submit a request for proposals. The unit of local government shall evaluate any sealed proposal from a qualified provider. The evaluation shall analyze the estimates of all costs of installations, modifications, or remodeling, including, without limitation, costs of a pre-installation energy audit or analysis, design, engineering, installation, maintenance, repairs, debt service, conversions to a different energy or fuel source, or post-installation project monitoring, data collection, and reporting. The evaluation shall include a detailed analysis of whether either the energy consumed or the operating costs, or both, will be reduced. If technical assistance is not available by a licensed architect or registered professional engineer on the unit of local government’s staff, then the evaluation of the proposal shall be done by a registered professional engineer or architect who is retained by the unit of local government. Any licensed architect or registered professional engineer evaluating a proposal under this Section may not have any financial or contractual relationship with a qualified provider or other source that would constitute a conflict of interest. The unit of local government may pay a reasonable fee for evaluation of the proposal or include the fee as part of the payments made under Section 20.