Most heat pump installations in Sunnyvale, Santa Clara and Cupertino replace a gas furnace and a central air conditioner that are wearing out at about the same time. One outdoor unit and one indoor air handler, or a set of ductless heads, then handle both heating and cooling. Mild winters and summer hot spells suit heat pumps well, but a good result depends on details settled before installation day: electrical capacity, duct condition, equipment size and where the outdoor unit can go. If your current system only needs a repair, the visit will say so; see heat pump repair.
Ducted, ductless or dual fuel?
| Option | Fits | What to know |
|---|---|---|
| Ducted heat pump with air handler | Homes with usable ducts in the attic or crawlspace | Replaces furnace and AC; ducts should be checked and sealed |
| Ductless mini-split heat pump | Eichler homes, additions, rooms the ducts never reached | One outdoor unit can serve several indoor heads |
| Dual fuel: heat pump plus gas furnace | A furnace with years left and an AC that has failed | Heat pump does most of the work; furnace backs it up |
Ductless mini-splits have their own page, including multi-room layouts.
Electrical capacity
A heat pump needs a dedicated 240-volt circuit, and switching from gas heat to electric adds load to the panel. Many older homes have smaller panels, so a load calculation comes before the equipment choice. Backup heat strips add a large electrical load, so they are sized only as large as the home needs. Our article on electrical panel upgrades for heat pumps goes into more detail.
Sizing and ducts
A heat pump is sized from a load calculation for both heating and cooling, not from the label on the old furnace. Its supply air is warm rather than hot, so airflow and duct leaks matter more than they did with a furnace: a leaky attic duct that went unnoticed with hot furnace air becomes a cold room with a heat pump. Undersized returns cause noise and weak airflow. Variable-speed equipment runs long, quiet cycles at low speed when the ducts allow it. Sealing and repairing ducts during the install is usually cheaper than doing it later; see duct sealing.
Placing the outdoor unit
- Keep the clearances the manufacturer lists around the coil and above the fan.
- Stay away from bedroom windows, yours and the neighbors’, if you can.
- In winter, defrost meltwater drains from the unit. A pad or stand where water will not pool on a walkway or freeze in the base keeps it clear.
- Line set length and height difference between indoor and outdoor units have limits that affect placement.
- In townhomes and condos, balcony and rooftop locations often need association approval before work starts.
Start-up and commissioning
A new heat pump should not be considered finished until it has been tested in both modes. Commissioning includes setting the refrigerant charge to the manufacturer’s specification for your line length, measuring airflow and static pressure, checking that defrost operates, and configuring the thermostat for a heat pump, with sensible auxiliary heat settings. Refrigerant work is done by EPA-certified technicians. You get a walkthrough of the thermostat and filter and the information needed to register the manufacturer’s warranty.
Avoiding a replacement you do not need
If the system is only a few years old and fails, a capacitor, a sensor or an airflow problem should be ruled out before anyone talks about new equipment. Ask for the readings behind a replacement recommendation. If you are still deciding between systems, the heat pump vs furnace guide and our furnace installation page cover the other side.
Local notes
Eichler homes in Sunnyvale and Cupertino heat through the slab and have no attic for ducts, so a heat pump there is usually ductless; many owners keep the radiant heat and add mini-splits for cooling. Newer townhomes and condos often have compact mechanical closets, which limits the air handler’s size. City pages: Sunnyvale, Santa Clara and Cupertino.