2025 Energy Code Highlights

The 2025 energy code makes a strong push toward all-electric new homes. It establishes a single-fuel baseline that prescriptively requires heat pumps for both space heating and water heating, effectively making electric heat pump systems the standard over gas-fired alternatives. Mandatory air supply requirements for heat pump water heater installations are a needed code assist for all the installers and inspectors in the field so they know how to ensure HPWHs work efficiently and don’t run us out of hot water. Additionally, requirements such as pool heater standards that move away from gas primary heaters promise significant utility cost savings over time. While these changes raise up-front construction requirements, they are expected to reduce long-term energy bills, cut greenhouse gas emissions, and accelerate the shift toward cleaner, more efficient homes.

The 2025 code also includes several terminology changes. Home Energy Rating System (HERS) Raters are now called Energy Code Compliance (ECC) Raters, and the units and terminology of the compliance metrics have changed. Instead of the Time-Dependent Valuation (TDV) metric used in past code cycles, performance compliance is now based on Long-term System Cost (LSC), which reflects the present value of energy system costs over a 30-year period. We see this as a rebrand, not a major tectonic plate shift.  What has always worked for compliance should continue to work. 

For new single-family homes in climate zones 4 and 8-15, the code also introduces a new Peak Cooling Energy metric that measures how much electricity a home uses for cooling during peak hours (4-9pm) from July through November. The intent is to prevent summer peak demand from being overlooked. Because LSC is designed around a future where winter heating with heat pumps becomes the dominant electric load, it can incentivize measures that reduce heating demand, such as higher SHGC windows and increased south-facing glazing. The Peak Cooling metric was added to ensure those design choices do not unintentionally increase summer grid stress in the meantime. Designs with lots of glass and skylights may run afoul of this new metric and require additional upgrades to compensate.

On multifamily projects, the biggest change as we see it is to ventilation requirements.  Exhaust ventilation for indoor air quality (IAQ) in dwelling units is now prohibited for the first time.  New multifamily buildings will have to install supply or balanced ventilation systems in units.  In many climate zones, HRV/ERVs will be prescriptive standard too, which may pave the path for HRV/ERVs to become the dominant IAQ method in apartment buildings for the first time.

The last change I’ll highlight is how heat pumps are modeled in the performance approach.  In the 2022 code cycle, we had a one-size-fits-all limited credit for minisplit heat pumps that was worth on average ~10% toward compliance.  We called this “VCHP”.  It was pretty simple to use this with ductless minisplit systems, but really complicated to use this with ducted minisplit systems, so the credit was useful on a small subset of projects.  Now, we can get compliance credit for a wide range of variable speed heat pumps – ductless, ducted, mixed, single speed, and variable speed.  More efficient systems will qualify for a larger credit of around the same 10% we got with the VCHP credit.  Less efficient systems will qualify for smaller credit, but that’s better than qualifying for no credit, which is how it worked in the past code cycle.  So expect different heat pump system selections in 2025 and expect your energy consultant to ask more questions about the HVAC system you would like to use, even specifying it in many cases.  We held a webinar on this topic for CEC staff, heat pump manufacturers, and CABEC in early 2026.

Here is a short bulleted list for those of 2025 energy code updates:

• Heat pumps and Heat pump water heaters prescriptive standard statewide
• New mandatory air supply requirements for Heat pump water heaters
• New mandatory maximum U-factor for windows and doors (0.40, measured as a weighted average of all new and altered windows and doors on the project)
• Pool heating regulations that prohibit gas pool heaters in primary position and encourage solar thermal collectors and Heat pump pool heaters
• HERS raters become ECC raters
• Compliance metrics go from TDV to LSC (Long-term System Cost)
• Added 4th compliance metric for new homes in CZ 4 & 8-15: Peak Cooling
• Exhaust ventilation prohibited in new multifamily building dwelling units; HRV/ERV prescriptive standard in many climate zones