On May 9, 2018, the California Energy Commission adopted the 2019 Title 24, Part 6 Energy Code updates that will take effect January 1, 2020. Key changes for new residential and non-residential projects include:

Residential (new ground up construction that has three habitable stories or less from grade):
1. The installation of solar photovoltaics will become mandatory. Square footage of the homes/units and number of bedrooms will help determine system sizing. For example, a 2,000 sq. ft. home in Los Angeles will require approximately 2.8 kW of solar PV and a 30-unit apartment building in Oakland will require approximately 30 kW. There are a few exemptions, such as buildings with minimal roof space due to a narrow envelope, zero lot area, or if there are tall buildings or other obstructions like protected tress blocking solar production.

2. New HERS (Home Energy Rating System) testing for:
a. Kitchen exhaust hood ventilation test, which must provide 100CFM at 3.0 Sones
b. Blower door test if utilizing a continuously running exhaust fan per Section 150.0(o)1E,
c. Quality insulation installation (QII) will be Prescriptively required.
d. HVAC systems will need to be designed closer to ACCA Manual J, D, & S which means duct sizing may increase, return air sizing may increase, and equipment sizing may decrease. There will need to be enough plenum space to ensure ducts are not smashed or pinched. Filter ratings will increase to MERV 13

3. Domestic hot water solar preheat will become Prescriptively required:
a. 20% net solar fraction in Climate Zones 1-9,
b. 35% net solar fraction in Climate Zones 10-16.

Non-Residential (Includes new multi-family four stories or more from grade)
1. Interior windows and doors leading to unconditioned space will have minimum Prescriptive U Factors.
2. Demand controlled ventilation (DCV): CO2 monitors will help control outside airflow.
3. The Prescriptive requirement for domestic solar hot water is being removed. Projects that install such systems will receive a major boost to whole building performance.

You can read more detail on the CEC website:

Energy Commission Adopts Standards Requiring Solar Systems for New Homes, First in Nation