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AC for ADUs, garage conversions and additions in Los Angeles
Most Los Angeles ADUs and garage conversions are cooled with a ductless mini-split heat pump, published at $4,000–$7,500 for one zone and $9,000–$12,500 for two in 2026. It heats as well, needs no ducts and runs separately from the main house.
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At a glance
The rebate most pages get wrong
LADWP's heat pump rebate does not apply to ADUs or new construction (LADWP, read 2026-10-20). Price an ADU system at full cost. GO ZERO is closed to new applications for now, and in its earlier phase it needed a gas furnace being replaced, which a new ADU does not have.
Why mini-splits are the default for ADUs
An ADU is small, often detached, and needs heat as well as cooling. A mini-split heat pump handles both from one outdoor unit without ducts, attic space or a gas line.
A studio or one-bedroom typically needs one or two heads. A ducted system makes more sense only in a larger ADU built with space for an air handler and ducts.
ADU cooling cost
| Mini-split, 1 zone E & A Mechanical, HVACProjectCost | $4,000–$7,500 |
| Mini-split, 2 zones E & A Mechanical | $9,000–$12,500 |
| Long refrigerant line set Reliable H&A, E & A Mechanical | +$300–$1,500 |
| Panel upgrade Reliable H&A, Cold Cloud, E & A Mechanical, HVACProjectCost | +$2,000–$7,500 |
Published LA ranges for houses; none of the sources prices ADUs separately. Full method on the cost guide.
Garage conversions and room additions
| Option | Suits | Watch for |
|---|---|---|
| Single-zone mini-split | Most conversions and additions | Outdoor unit placement, line-set route |
| Extend existing ducts | A small addition next to a system with spare capacity | An undersized system, longer duct runs, Title 24 testing of the extension |
| Separate ducted system | Large additions | Space for an air handler |
Garages were built with little or no insulation, a slab floor and a large door opening. Insulation and window choices set the cooling load, so finalize them before anyone sizes the system. Size from the converted space as it will be built, not from the old garage.
Location matters too: a west-facing addition in the Valley, where Woodland Hills averages 115.3 days a year at 90 °F or above (NOAA normals), needs more than the same room near the coast. Tying a conversion into the existing AC works only if the whole-house load leaves spare capacity; ask the contractor to check it first.
Mini-split or extend the house system?
Separate mini-split
- Own thermostat and controls
- No duct run across the yard
- Heats and cools
- Separate outdoor unit to place
Extend the main system
- Only for attached spaces close to existing ducts
- Needs spare capacity in the house system
- One thermostat for both
- The extension is tested under Title 24
How ADU cooling gets built
- Finalize the envelope. Insulation, windows and orientation set the load; size after they are fixed.
- Load calculation on the ADU as it will be built.
- Electrical plan. Subpanel or meter, and the HVAC circuit within it.
- Outdoor unit location agreed against setbacks and neighbors' windows.
- Permit under the ADU building permit, or a separate mechanical permit for an existing ADU.
- Install, test and inspect with the rest of the ADU sign-offs.
What sets the size of an ADU system
| Factor | Pushes the load up | Pushes it down |
|---|---|---|
| Location | Valley, inland | Coast |
| Orientation and glass | West-facing windows, glass doors | Shaded, north-facing, smaller windows |
| Roof and ceiling | Vaulted ceilings, little insulation | Insulated attic or roof deck |
| Garage conversions | Slab floor, old door opening, thin walls | Insulated walls and a properly filled-in door opening |
The contractor should size from the ADU as it will be built. HyreHVAC explains what a load calculation measures.
Electrical capacity
A new ADU adds load to a lot that may share one service. The HVAC circuit has to fit within it, alongside a kitchen and water heater. Whether the ADU has its own subpanel or meter changes what the HVAC contractor needs to run. Ask for the electrical scope in writing.
How the permit works
For a new ADU, the cooling system usually goes in under the ADU's own building permit and energy compliance paperwork. Adding a system to a finished ADU is a separate mechanical permit. Either way the office is LADBS in the City of Los Angeles or your city or county office; see the permit guide.
What to ask
- One zone or two, and what load calculation supports it?
- Where will the outdoor unit sit relative to the property line and the neighbor's windows?
- Does the panel or subpanel have room for the circuit?
- Is this under the ADU permit or its own mechanical permit?
- Have you priced it without any LADWP rebate, given ADUs are excluded?
Compare quotes in the quote tool.
Sources
- E & A Mechanical (Tujunga), heat pump installation cost in Los Angeles (retrieved 2026-09-29)
- HVACProjectCost.com, Los Angeles HVAC replacement cost (retrieved 2026-09-29)
- Reliable Heating and Air (Woodland Hills), AC installation cost in LA and Ventura County (retrieved 2026-09-29)
- California Energy Commission, "Building Energy Efficiency Resources for Single Family Homes" (retrieved 2026-09-29)
- NOAA NCEI, U.S. Climate Normals 1991–2020, annual/seasonal (stations USW00023174, USW00093134, USW00023152, USC00049785) (retrieved 2026-09-29)
- LADWP, "Consumer Rebate Program" (Heat Pump HVAC) (retrieved 2026-10-20)
- South Coast AQMD, "GO ZERO Incentive Program" (retrieved 2026-10-20)
Questions
What AC system is best for an ADU in Los Angeles?
For most detached ADUs and garage conversions, a ductless mini-split heat pump: it heats and cools, needs no ducts, and one or two zones cover a small unit. Published LA prices are $4,000–$7,500 for one zone and $9,000–$12,500 for two.
Can the ADU share the main house's AC?
Extending the main system's ducts to a detached ADU is rarely practical and puts both on one thermostat. An attached ADU or addition close to the existing ducts may be an exception. Separate systems also let each unit be metered and controlled on its own.
Can I tie a garage conversion into my existing AC?
Sometimes, if the existing system has spare capacity and a duct can reach the space. Ask the contractor to run a load check on the whole house first; an overloaded system cools both spaces poorly.
Does an ADU heat pump get the LADWP rebate?
No. LADWP's Consumer Rebate Program page, read on 2026-10-18, says accessory dwelling units and new construction are not eligible for its heat pump HVAC rebate. Some ranking pages miss this; do not subtract it from an ADU quote.
Does the AQMD GO ZERO rebate cover an ADU?
GO ZERO is closed to new single-family applications (checked 2026-10-20) while Phase 2 is set up. In its earlier phase it paid only when a heat pump replaced a gas or propane furnace, which a new ADU does not have.
What size mini-split does an ADU need?
It depends on the ADU's insulation, windows, orientation and location, which is why the contractor should run a load calculation on the unit as built. A detached studio in the Valley needs more capacity than the same studio near the coast.
Should the ADU have its own electrical meter for the AC?
That is an electrical and permit decision for the ADU as a whole. For the HVAC contractor it changes where the circuit comes from and how much capacity is left. Settle it before the HVAC quote.
Where should the ADU's outdoor unit go?
Somewhere with airflow, a short line-set route to the heads, and distance from the main house's and the neighbor's windows. On small lots the setback and noise are the limits; settle the location before the permit drawings are final.
Can one outdoor unit serve both the house and the ADU?
A multi-zone outdoor unit can technically serve heads in both, but it ties the two buildings to one system and one point of failure, and complicates separate metering. Most owners keep them separate.
Is the AC part of the ADU permit?
For a new ADU, the HVAC is normally part of the building permit and its Title 24 energy compliance. For a mini-split added to an existing ADU, it is its own mechanical permit. Confirm with the permit office for the address.
Next step
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- Compare what comes back. Line the written quote up against the published ranges and the quote checklist.
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