Heat Pump Installation and Repair in Atherton, CA

A Homeowner’s Guide to Heat Pump Installation and Repair in Atherton

Installing a heat pump in Atherton takes a Town building permit, and the outdoor unit has to sit within the lot’s buildable area, screened for noise, clear of existing trees and under the Town’s night limit of 50 dBA. Gas furnaces aren’t banned, but WestLight Energy rebates heat pumps that replace them, and the Air District’s zero-NOx furnace rule starts in 2029.

Permits from the Town Building Department

The Town’s list of work exempt from permits, written for the 2022 codes, leaves very little HVAC work out: portable heaters and coolers, part replacements that don’t change the equipment’s approval, and self-contained refrigeration systems with ten pounds of refrigerant or less. Replacing a furnace or AC with a heat pump is permit work. Applications and plans go to the Building Department, 80 Fair Oaks Lane, through its ePlan upload; questions go to (650) 752-0560 and inspection requests to (650) 752-0542.

Where the outdoor unit can go

Atherton’s zoning code treats outdoor cooling equipment in section 17.40.030(B)(12). As of October 2026, air conditioners and generators need no zoning permit when they:

Condition	What the code says
Location	Within the buildable area of the lot; may sit next to existing buildings
Screening	Enclosed or otherwise screened to reduce noise
Noise	Comply with the Town noise ordinance
Trees	The location must not affect existing trees
Underground units	No more than 6 inches above grade

The section doesn’t name heat pumps, so we confirm the spot with the Town before setting a pad. The tree condition deserves care, because heat pump work includes a line set, a condensate drain and electrical runs that shouldn’t cross root zones.

Noise limits

Section 8.16.030 of the Municipal Code sets 60 dBA from 7 a.m. to 10 p.m. and 50 dBA from 10 p.m. to 7 a.m., measured at the outside perimeter of the complaining property. A steady, audible tone, like a compressor hum, lowers each limit by 5 dBA. Unlike a summer-only AC, a heat pump runs through winter nights, so we compare the unit’s rated sound with its distance to the nearest neighbor. Inverter models, which slow down rather than switch on and off, often run quieter at night. See common HVAC noises.

Title 24 checks on a changeout

The California Energy Commission’s 2025 guidance for single-family alterations sets these checks:

• Refrigerant charge is verified for heat pumps in every climate zone.
• Ducts are sealed and tested when either the indoor or outdoor unit is replaced: 10% total leakage or 7% to outside, or a smoke test confirming accessible ducts are sealed.
• Load calculations are required for new systems.
• Refrigerant recovery from the old system is done by an EPA 608 Type II or Universal technician.

See duct repair if testing finds leaks.

The reach code, the furnace rule and WestLight

The Town’s Electric Readiness Reach Code, described in its Summer 2025 newsletter and still listed in the Municipal Code (§ 15.19.030), doesn’t require replacing gas appliances. For additions and alterations that need an electrical permit, a utility room with a gas or propane furnace must meet the Energy Code’s heat pump readiness rule, section 150.0(t). The Air District’s Rule 9-4 sets zero NOx for furnaces manufactured after January 1, 2029.

WestLight Energy pays a rebate per outdoor or packaged unit, up to two per account, when a heat pump replaces gas, propane, oil or a wood stove; ducted and ductless both qualify, and dual-fuel systems don’t. Install, then apply within 90 days with the Town permit. A panel upgrade within 6 months of the heat pump earns a bonus; panel work is done by a licensed electrician. See WestLight Energy rebates.

Sources

Town of Atherton: Work exempt from building permits · Building ePlan submittal · General building information · Athertonian, Summer 2025 (reach code update) · Municipal Code § 8.16.030 · Municipal Code ch. 17.40 · Municipal Code ch. 15.19. California Energy Commission: 2025 Single-Family HVAC. WestLight Energy: Appliance rebates · Heating and cooling upgrades. Bay Area Air District: Building Appliances Rule Implementation. Checked October 2026.