The main system types
| System | How it works | Often the best fit for |
|---|---|---|
| Gas furnace + central air | Furnace heats with gas; outdoor unit cools; both share the ducts | Homes with ducts and a gas supply; the most common setup in Southern California |
| Heat pump | One outdoor unit heats and cools with electricity; indoor air handler shares the ducts | Mild climates like ours, homes with solar, owners moving away from gas |
| Dual fuel | Heat pump for most of the year, gas furnace for the coldest mornings | Owners who want heat-pump efficiency with gas as backup |
| Ductless mini-split | Outdoor unit feeds slim indoor units room by room, no ducts | Additions, converted garages, ADUs, homes without ducts, single problem rooms |
| Packaged unit | All components in one cabinet on the roof or beside the building | Homes with no indoor space for equipment; many commercial buildings |
| Hydronic or radiant | Boiler heats water that warms radiators or floors | Homes built around them; radiant floors in remodels |
Four questions that decide it
What is your home like? Size and age, how well it is sealed and insulated, how many windows face west, how much shade it gets. Older homes lose more heat and gain more in summer than newer ones.
What is already there? If you have ducts in good condition, ducted systems are usually simplest. If you have a boiler, staying hydronic is usually wiser than adding ducts. If you have no ducts at all, ductless may be the elegant answer.
What energy do you have? Gas, electricity or both, and what each costs at your address. Rooftop solar changes the math in favor of electric heating.
How do you live? Which rooms are used and when, whether anyone is sensitive to dust, dry air or noise, and whether some rooms always feel different from the rest.
Budget matters too, in two ways: what the system costs to install, and what it costs to run for the next fifteen years or more.
Size matters more than you think
A system that is too large is not a safety margin. It cools the house in short bursts, switches off before it has removed the moisture, and leaves rooms feeling cold and clammy. The constant starting and stopping is noisy and wears it out sooner.
A system that is too small runs flat out on the hottest afternoons and still falls behind.
The right size comes from a proper load calculation: a room-by-room assessment of how much heating and cooling your home actually needs, based on its size, insulation, windows, orientation and air tightness. Rules of thumb such as "one ton per so many square feet" are shortcuts, and they are often wrong.
Do not forget the ducts
The ducts deliver everything your system produces. Leaky, crushed or undersized ducts can waste a large share of that energy in the attic and leave rooms short of air, no matter how good the equipment is. In California, most equipment replacements also require the ducts to be tested for leakage under the state's energy code.
What a good consultation should include
Whoever you choose to work with, a sound recommendation should come from:
- A walk through your home, including the attic or crawlspace where the ducts run.
- Questions about how you use your home and what bothers you about it now.
- A load calculation, not a guess based on the old system's size.
- A look at your ducts, filter and electrical supply.
- Clear options with their installed cost, likely running cost and warranty, in writing.