Wikipedia definition for Title 24 Energy Calculations:
The California Energy Code, or Title 24, Part 6 of the California Code of Regulations, also titled The Energy Efficiency Standards for Residential and Nonresidential Buildings, were established in 1978 in response to a legislative mandate to reduce California's energy consumption. The standards are updated periodically to allow consideration and possible incorporation of new energy efficiency technologies and methods.
The 2016 Energy Standards have set out to simplify and clarify several areas that were new in the 2013 Energy Standards. The focus on the 2016 Code will be the building envelope, i.e. high performance walls and attics, integrating renewable such as PV credit, lighting (LEDs) and making tankless water heaters part of the standard design. The 2016 Energy code is the final prep for 2020 ZNE (Zero Net Energy).