Section C406.5. Total minimum ratings of on-site renewable energy systems shall comply with one of the following: 1. Provide not less than 1.75 Btu (1850 W), or not less than 0.50 watts per square foot (5.4 W/m2) or conditioned floor area. 2. Provide not less than 5 percent of the energy used within the building for building mechanical and service water heating equipment and lighting regulated in this chapter.