What does the 2025 Energy Code require for a new home's MEP systems?

For a new single-family home, the 2025 Energy Code makes heat pumps the prescriptive baseline for space heating in every climate zone and points water heating toward heat pump water heaters. It also requires battery-ready electrical equipment for homes with service over 125 amps and electric-ready provisions wherever gas appliances are installed. It applies to permit applications submitted on or after January 1, 2026.

Mechanical

• Heat pump baseline. Prescriptively, heating equipment must be a heat pump in all climate zones; other systems must comply through the performance approach.
• Heat pump controls. New mandatory rules limit supplementary heat to outdoor temperatures below 35 degrees F (with exceptions), require defrost delay timers of 90 minutes or more in many climate zones, and cap electric resistance supplementary heat capacity. Installers certify these on the CF2R.
• Sizing. Heat pump heating capacity must meet the California Building Code minimum without counting supplementary heat.
• Verification. Refrigerant charge verification is required prescriptively for heat pumps in all climate zones.
• Ventilation. Whole-dwelling ventilation now has added requirements for balanced and supply-only systems, including access to filters and recovery cores, and a fault indicator display for HRV and ERV systems.

Plumbing and water heating

• Prescriptive options are a heat pump water heater, with added measures in some climate zones, or a solar water heating system with electric backup; other types can comply through the performance approach.
• The gas tankless exception for homes with heat pump space conditioning was removed.
• Heat pump water heaters have new installation rules for backup heat and for ventilation or minimum room volume.

Electrical

• Battery-ready. New one- and two-unit homes with service over 125 amps need battery energy storage readiness, unless a battery is installed.
• Electric-ready. If you install a gas water heater, cooktop, dryer or furnace, the code requires dedicated 240-volt circuits or space and reserved breakers for future electric equipment, such as 30-amp for a heat pump space heater, 50-amp for a cooktop and 30-amp for a dryer.
• Solar PV. PV sizing now accounts for solar access roof area.
• Lighting. All luminaires and light sources must meet JA8, with some new exceptions.

Verification and paperwork

The 2025 code moves the former HERS program into the Energy Code Compliance (ECC) program. Compliance documents are registered with an ECC provider, and inspectors check that verifications are complete before final.

What this means for your MEP plans

The mechanical schedule, panel layout, water heater location and Title 24 report all need to agree from the start. MEP Plans USA prepares complete residential MEP plans and Title 24 reports for new California homes, with two revisions and city plan-check corrections included. See residential MEP plans, Title 24 reports and battery-ready requirements. Local reach codes can add requirements, so confirm with your building department.

Sources: energy.ca.gov, energy.ca.gov, energy.ca.gov.