Most air conditioners installed in San Jose replace a unit that has worn out: builder-grade equipment in an Evergreen tract home, an R-22 system that has leaked once too often, or an older unit that never kept the upstairs bedrooms comfortable. Some houses are getting central air for the first time. Either way, the job is more than swapping one box for another. Size, ducts, electrical supply and refrigerant all have to suit the house, and the free in-home estimate looks at each before you choose equipment.
Size it from a load calculation, not the old nameplate
The tonnage on the old unit only tells you what someone picked years ago. Since then the house may have gained new windows, more insulation, a room addition or a converted garage. A load calculation works from the house as it is now: floor area, insulation, window size and direction, ceiling height and where the ducts run.
- Too big: the system cools the air fast, shuts off and starts again minutes later. Rooms swing between cool and stuffy, moisture stays in the air and the equipment wears faster.
- Too small: it runs nonstop through a hot valley afternoon and never reaches the setting.
Evergreen tract homes show this often. The original equipment was sized when the houses were built, and the house as it stands today is what matters. Larger Almaden Valley homes, some over 3,000 square feet, raise a different question: whether one large system, two systems, or one system with zoning will keep both the far bedrooms and the main rooms comfortable.
The ducts decide how well it cools
A new high-efficiency unit on leaky ducts throws away much of what it gains. In older Willow Glen and Cambrian homes the ducts are often original, thinly insulated and running through an attic that bakes all summer. Cool air leaks into the attic, hot attic air is drawn into the returns, and the rooms at the end of the longest runs never get enough.
California’s energy rules can require a duct leakage test when major equipment is replaced, so the condition of the ducts is part of the job, not an extra. Depending on what the inspection finds, ducts are sealed, partly replaced or replaced throughout. Undersized returns are common in older houses too; they make any new system louder and weaker.
Check the electrical panel before choosing equipment
Central air needs its own 240-volt circuit, sized to the breaker rating on the unit’s nameplate, and a disconnect within sight of the outdoor unit. In older San Jose homes the panel may be small or already full. Adding central air to a house that never had it, or moving from a gas furnace to a heat pump, can push the electrical service past what it was built for. We check panel space and capacity at the estimate. If an electrician needs to upgrade the panel, you know before you commit, not on installation day.
Refrigerant: what has changed
R-22 has not been produced in the US since 2020, so systems that still use it run on recovered and stored refrigerant, and every leak repair is expensive. New equipment has largely moved past R-410A as well, to refrigerants such as R-454B or R-32. These are classed as mildly flammable and come with their own installation requirements, and the indoor coil must match the outdoor unit and its refrigerant. In practice a replacement usually includes a new indoor coil, and the existing copper lines are reused only when their size and condition allow.
Choosing the equipment
- Single-stage units run at full output or not at all. They are the simplest and cost the least.
- Two-stage and variable-speed units spend most of their time at lower output: steadier temperatures, better moisture removal and quieter running. They suit larger homes and houses with a hot second floor.
- Efficiency is rated in SEER2. A higher rating costs more up front and pays back faster in homes that run the AC for long hours, which describes the valley floor more than the hillsides.
If the furnace is old too, a heat pump replaces both and adds efficient heating. For a house with no ducts, ductless mini-splits avoid opening walls and ceilings. Our brand comparisons explain how the major equipment lines differ.
What moves the price
Installed central air typically runs $4,500 to $15,000. Within that range, the price depends on:
- the size of the system, its efficiency and its staging;
- whether the indoor coil, furnace or air handler is replaced at the same time;
- duct sealing, repairs or replacement;
- electrical work, from a new circuit to a panel upgrade;
- a first-time installation (new pad, line set and drain) versus a replacement.
How an installation goes
- Free in-home estimate. Load calculation, duct and panel check, and written options with prices.
- Permit. We pull it and arrange the inspection.
- Installation day. The old refrigerant is recovered, the new equipment is set, and the lines are pressure tested, evacuated and charged.
- Startup and handover. Airflow, temperatures and charge are measured. You get a walk-through of the thermostat and filter, plus the paperwork for the manufacturer’s warranty.
Not sure the old system is finished? The repair-or-replace guide helps you decide. For Berryessa, where homes vary from street to street, see AC installation in Berryessa.