The Building Code to Net-Zero

California continues to be a national energy leader with cost-effective regulation


California has made great strides in energy savings in the building sector. The state set energy-use reduction goals targeting zero-net-energy use in all new homes by 2020 and commercial buildings by 2030. The goal meant that new buildings would use a combination of energy efficiency and distributed renewable energy generation to meet all annual energy needs. Homes built in 2020 and beyond will be highly efficient and will include photovoltaic (PV) generation to meet the home’s expected yearly electric needs.

The California Energy Commission (CEC) estimates that new, energy efficient single-family homes will use about seven percent less energy versus those built under the 2016 California Energy Code. Once onsite solar generation is factored in, these homes will use about 53 percent less energy than those under the 2016 code, reducing greenhouse gas emissions by 700,000 metric tons over three years.

Some 2019 California Energy Code highlights include:

  • Requiring solar PV systems for new homes.
  • Encouraging demand-responsive technologies (battery storage and heat pump water heaters).
  • Improving a building’s thermal envelope through high performance attics, walls and windows to improve comfort and energy savings.
  • Including the new Energy Design Rating (EDR) compliance path.
  • Enabling the use of highly efficient air filters.

The CEC further indicates that the 2019 California Energy Code will increase the cost of constructing a new home by about $9,500, but will save $19,000 in energy and maintenance costs over 30 years. Based on a 30-year mortgage, they estimate that the 2019 California Energy Code will add about $40 per month for the average home, but save consumers $80 per month on heating, cooling, and lighting bills.

For more than five years the Residential Energy Services Network (RESNET) and the CEC have worked together to bring the California and RESNET energy rating standards into harmony.

The addition of the EDR compliance path to the 2019 California Energy Code moves the two organization’s rating systems closer to alignment. The California EDR is similar to the RESNET HERS (Home Energy Ratings System) Index in that the reference home score is 100 with every percentage of energy reduced representing a score reduction of one point.

RESNET’s HERS Index is based on the ANSI/ RESNET/ICC Standard 301 which is also known as the Energy Rating Index (ERI). In 2015 the ERI was incorporated as a compliance path in the International Energy Conservation Code® (IECC®). The RESNET HERS Index and ERI both use the 2006 IECC as the basis for the reference home—the home by which the rated (or proposed) home is compared.

During the development of the 2019 California Energy Code, the new EDR compliance path replaced the previous “Compliance Percent” performance path. One of the most important changes with the new EDR path is that the reference home for that path is also based on the 2006 IECC, meaning the EDR and RESNET’s HERS index are very close to being in harmony.

There are still some variations differentiating the EDR and RESNET HERS scores. One major difference is that the EDR is based on Time Dependent Valuation (TDV), which considers when energy is used in addition to the amount used. Measuring TDV allows California to encourage reduction of peak demand loads.

Another innovation of the 2019 California Energy Code is an allowance for the use of battery storage for photovoltaics to lower the EDR score, thus representing another change in the importance of peak demand loads. This innovation presents a pathway for the HERS Index to reflect the equivalent importance of knowing the timing and quantity of energy use.

The decision to move to the EDR compliance path was a way for California to better meet the State of California’s policy to net zero energy buildings. EDR also allows for a metric that can be used to determine whether a home can achieve net zero energy. California’s 2019 Energy Code requires new homes to first meet an efficiency target EDR score and then meet a solar PV target EDR score. Doing so ensures a minimum level of energy efficiency is achieved prior to the use of renewable energy, thereby reducing the size of a solar PV array required to achieve net zero energy.

This change in Title 24 to create a new EDR compliance path is an important step. It brings the RESNET HERS Index closer into alignment with the California Energy Code and provides an example by which future versions of the IECC could be modeled to achieve a net zero energy code for the rest of the country.

As part of this effort, the CEC has selected measures for inclusion in the 2022 code cycle. These updates will continue to improve upon the 2019 standards for new construction and additions and alterations to residential and nonresidential buildings.

David Walls is the Vice President of Business Support Initiatives for the International Code Council (ICC). His responsibilities include overseeing the development of support products and materials related to sustainability as well as domestic and international business development activities. For more information on the 2019 California Energy Code and other newly published codes for California, please visit