THE SHORT ANSWER
A heat pump heats and cools your home by moving heat, so one system can do the work of both an air conditioner and a furnace. The Department of Energy describes heat pumps as an energy-efficient alternative to furnaces and air conditioners for all climates. An AC and furnace can still be the better fit if you plan to keep part of a working system or your ducts or electrical panel point to a different scope. Compare both for your house before you decide.
KEY TAKEAWAYS
- A heat pump moves heat rather than generating it, so the same system can cool your home in summer and heat it in winter.
- Ducted heat pumps use existing ducts, and ductless mini splits do not need any, so the condition of your ducts shapes the choice.
- ENERGY STAR says a contractor should verify the right size with a load calculation called Manual J. Undersized and oversized systems both struggle.
- Under the 2025 Energy Code, replacing the outdoor unit or the indoor unit of a split system, by itself, triggers duct sealing and field verification. Heat pumps also need refrigerant charge verification in all climate zones.
HOW DOES A HEAT PUMP DIFFER FROM AN AC AND FURNACE?
The Department of Energy says heat pumps use electricity to transfer heat rather than generate heat. In the cooling season, a heat pump moves heat from inside your home to the outdoors. In the heating season, it moves heat from the outside air into your home. ENERGY STAR describes the same thing: a heat pump pulls heat out of your home in the summer, extracts heat from the outside into your home in the winter, and moves heat rather than converting it from fuel.
An AC and furnace split the job between two pieces of equipment: the air conditioner cools and the furnace heats. A central air conditioner and furnace typically share the home's forced-air ducts. ENERGY STAR says that in most zones an air-source heat pump can be installed as a drop-in replacement when a central air conditioner or furnace needs replacing, and the Department of Energy says that for homes with existing ductwork, replacing a furnace with a heat pump or installing a hybrid system is often easier.
| Question | Heat pump | AC plus furnace |
|---|---|---|
| What does it do? | Heats and cools with one system by moving heat | An air conditioner cools and a furnace heats, as two pieces of equipment |
| Ducts | Ducted models use the home's forced-air ducts; ductless models need none | A central AC and furnace typically share the home's forced-air ducts |
| Replacing what you have | ENERGY STAR says an air-source heat pump can be a drop-in replacement for a central AC or furnace in most zones; your ducts and panel still need to be checked | Replacing like for like keeps the same equipment types; the same duct, permit and testing questions apply |
| Electrical | Runs on electricity, so ask whether your panel and circuits can serve the new equipment | Ask what your current equipment draws and what the new equipment needs |
| Permit and testing | A permit; duct sealing and verification, and refrigerant charge verification in all climate zones | A permit; the same duct tests when the outdoor or indoor unit of a split system is replaced; refrigerant charge verification for air conditioners in climate zones 2 and 8 through 15 |
| When it may fit better | You want one system for heating and cooling, or a ductless option for a room or a home without ducts | You plan to keep part of a working system, or your ducts or panel point to a different scope |
- U.S. Department of Energy, Energy Saver: Heat Pump Systems (opens in a new tab)
- ENERGY STAR: Air-Source Heat Pumps (opens in a new tab)
- California Energy Commission: 2025 Single-Family Heating, Ventilation, and Air Conditioning (HVAC) (opens in a new tab)
- California Energy Commission: 2025 Single-Family Residential Compliance Manual, Chapter 9 (alterations and repairs to existing homes) (opens in a new tab)
IS A HEAT PUMP A GOOD FIT FOR SOUTHERN CALIFORNIA?
The Department of Energy describes heat pumps as an energy-efficient alternative to furnaces and air conditioners for all climates. A heat pump heats and cools with one outdoor unit and suits Southern California's mild winters, and many homes are good candidates.
Your address still matters more than the region. NOAA explains that the marine layer forms when cold ocean water cools the air above it, and the National Weather Service in San Diego says the weather can be very different between beaches and inland areas. A home near the water and a home farther inland can ask different things of the same system, as can a shaded, well-insulated house and a sunny one with large west-facing windows.
The Department of Energy also describes dual-fuel (hybrid) systems, which pair a heat pump with a gas furnace. The heat pump handles most of the heating in milder weather and the furnace takes over when temperatures drop. Ask whether that setup makes sense for your home or whether a heat pump alone is enough.
SHOULD I CHOOSE A DUCTED HEAT PUMP OR A DUCTLESS MINI SPLIT?
ENERGY STAR says ducted air-source heat pumps can connect to the forced-air ductwork common in most American homes, while ductless (mini split) heat pumps do not need ductwork. A ductless system mounts one or more head units on an interior wall or ceiling and connects them to an outdoor unit with refrigerant lines. The Department of Energy calls mini splits an efficient and flexible solution for homes without existing ductwork and says they are generally the best retrofit option for those homes.
| Question | Ducted heat pump | Ductless mini split |
|---|---|---|
| Ductwork | Connects to the home's forced-air ducts | Needs no ducts |
| Indoor equipment | Air moves through the existing ducts | One or more head units on an interior wall or ceiling |
| Where it fits | Homes with existing ductwork | Homes or sections of homes without ductwork, rooms with hot or cold spots, and spaces where ducts are hard to extend |
| What to ask | Are the ducts sealed, in good shape and right for the new equipment? | How many head units do you need, and where can each one and the outdoor unit go? |
| Outdoor unit | Ask where the outdoor and indoor equipment will go | ENERGY STAR advises allowing unobstructed airflow around the outdoor unit and considering access for service |
WHAT SIZE HEAT PUMP DOES MY HOME NEED?
ENERGY STAR calls properly sized equipment essential to the best performance and comfort, and says undersized or oversized systems struggle to meet comfort needs. It says a contractor should verify the right size with a load calculation called Manual J.
Square footage alone does not set the answer. Insulation, windows, sun exposure and ductwork all change the load, so a replacement is best sized to the house rather than by simply matching the old unit.
WHAT DO THE PERMIT AND THE 2025 ENERGY CODE REQUIRE FOR A CHANGEOUT?
CSLB's HVAC checklist tells homeowners to make sure the contractor obtains a building permit from the local building department and that the building department performs all required inspections. The California Energy Commission says buildings whose permit applications are applied for on or after January 1, 2026 must comply with the 2025 Energy Code.
- Duct sealing and verification: the Energy Commission's 2025 Single-Family HVAC page says replacing the outdoor unit or the indoor unit of a split system, by itself, triggers duct sealing and field verification. An independent rater, called an ECC-Rater, verifies the result.
- Refrigerant charge: the Commission's compliance manual calls for refrigerant charge verification on heat pumps in all climate zones, and on air conditioners in climate zones 2 and 8 through 15.
- Permit: your city or county building department sets how a heat pump changeout is permitted. Ask it how a job that also needs a new circuit or panel work is handled.
We do not assign climate zones to cities. Ask your contractor or building department which zone your address is in and which of these tests apply.
- CSLB: HVAC Installation Fact Sheets and HVAC Checklist for consumers (PDF) (opens in a new tab)
- California Energy Commission: 2025 Building Energy Efficiency Standards (opens in a new tab)
- California Energy Commission: 2025 Single-Family Heating, Ventilation, and Air Conditioning (HVAC) (opens in a new tab)
- California Energy Commission: 2025 Single-Family Residential Compliance Manual, Chapter 9 (alterations and repairs to existing homes) (opens in a new tab)
WHAT SHOULD I ASK ANY CONTRACTOR BEFORE CHOOSING?
- How will you size the system? Ask whether the answer comes from a load calculation of the house.
- What condition are my ducts in, and will they be sealed and verified? Would a ductless option suit part of the house?
- Can my electrical panel and circuits serve the new equipment, and is any electrical work part of the proposal?
- Where will the outdoor unit and indoor equipment go, and is that spot clear of obstructions?
- Who pulls the permit, and who schedules the inspections and the Energy Code testing?
- If my home is in a homeowners association, who handles the association's review?
If your home is in a homeowners association that requires approval for physical changes, Civil Code Section 4765 sets the ground rules for that review: the association's decision is to be in writing, and a disapproval has to explain why and describe how to ask for reconsideration. HOA approval and a city permit are separate. One does not replace the other.