How do all-electric mandates affect mechanical plans?

In California cities that have adopted all-electric "reach codes," gas-burning HVAC is prohibited in new ADU construction — meaning the mechanical plan cannot show a gas furnace, gas space heater, or the gas piping and venting that serve them. The required alternative is all-electric equipment, most commonly a mini-split or ducted heat pump, which is why these mandates have made heat pumps the default on nearly every new ADU mechanical plan.

What an all-electric mandate removes from the plan

Dozens of California cities — including Los Angeles, San Jose, San Francisco, Oakland, Berkeley, and Sacramento — have adopted ordinances restricting natural-gas infrastructure in new buildings. Where these reach codes apply to ADUs, the mechanical plan cannot include:

• Gas furnaces or gas-fired space heaters.
• The gas piping, meters, and vent/flue systems serving mechanical appliances.
• Combustion-air provisions for those appliances (no longer applicable with no gas equipment).

What the mechanical plan shows instead

Under an all-electric mandate, the compliant ADU mechanical design centers on:

• Heat pump space conditioning — a ductless mini-split or ducted heat pump for heating and cooling in one all-electric unit, which also satisfies the code requirement to maintain 68°F in every habitable room.
• Electric-resistance backup or supplemental heat only where engineering justifies it.
• ASHRAE 62.2 ventilation — unchanged by the gas question, but always documented.

Removing gas also simplifies the drawings: no flue routing, no combustion-air calculations, and tighter coordination with the electrical plans, since the panel must be sized for the higher all-electric load.

An important nuance: it depends on your address

There is no single statewide gas ban. Whether gas equipment is prohibited depends entirely on whether your jurisdiction has adopted an all-electric ordinance and how it is written — some apply only to new detached construction, some exempt certain appliances, and some are structured as energy-code amendments rather than outright bans. Because these reach codes change frequently and have been the subject of ongoing legal developments, confirm the current rule with your local building department before finalizing the mechanical design.

Even in cities that still permit gas, the 2025 California Energy Code strongly favors heat pumps. Many owners choose all-electric voluntarily to future-proof against expanding restrictions and to simplify Title 24 compliance.

All-electric mechanical checklist

1. Confirm whether your city has an active all-electric reach code and whether it applies to your ADU type.
2. If it applies, remove all gas appliances, piping, and venting from the mechanical plan.
3. Specify a heat pump for space conditioning, sized from a Manual J.
4. Coordinate the higher electrical load with the electrical plans (panel capacity).
5. Keep the equipment consistent with the Title 24 energy report.

All-electric ordinances and exemptions vary by jurisdiction and change frequently — confirm current details before you design. Our mechanical plans are built around your city's requirements, and the Full MEP package keeps mechanical, electrical, and plumbing coordinated under an all-electric design. Order here when ready.