In Houston the lowest hanging fruit is HVAC, insulation, lighting (indoor and outdoor), cool roofs (reflective white roof), energy management systems, elevator modifications, car charging stations, bike racks, windows, glazing. HVAC components include chillers, cooling towers, air handlers, thermostats, boilers, variable drive fans (VDF's).
Water conservation improvements are also included, such as low flow toilets and showers, irrigation, rain water collection and native landscaping.
Renewable energy including solar, wind and geothermal projects are also included.
PACE specifically includes soft costs such as architectural, engineering, audits, advisory and financing fees.
Generally, if the improvement touches and electron or a water molecule, it can be included if its annual cost, financed over its useful life, is projected to be less than the money saved through lower utility bills.