Mini-Split vs Central AC for Older California Homes

Why this comes up so often in San Diego

A huge share of North County San Diego homes — Oceanside bungalows, Carlsbad ranchers, Encinitas beach cottages, Vista mid-century houses, Coronado century-olds — were built before central air was standard. Many have never had cooling, just whatever heating fit at the time. Now those same homeowners want comfort without tearing the house apart.

That's the real choice on the table: retrofit central AC into a home not built for it, or install ductless mini-splits zone by zone.

When mini-splits win

• No usable ductwork. Putting in central AC requires either retrofitting ducts (expensive, invasive — soffits, dropped ceilings, sometimes attic-only routing that misses the rooms that matter) or installing a high-velocity small-duct system (loud, not cheap). Mini-splits skip the duct problem entirely.
• Room-by-room control. One mini-split head per zone means the master bedroom can be 68°F at night while the rest of the house is 74°F. Central AC can't do that without expensive zoning kits.
• Garage conversions, ADUs, finished basements. A mini-split is the cleanest way to add cooling and heating to a single space without re-engineering the main system.
• Historic / character homes. Coronado, North Park, Hillcrest, Mission Hills — homes where you do not want soffits and ductwork chases destroying the architecture.
• Renters / owner-occupants who only need partial cooling. A two-zone mini-split for the master + living room is often half the cost of central AC and covers 90% of comfort moments.

When central AC wins

• You already have ductwork. If existing ducts are in decent shape and duct sealing can hit Title 24 spec, a central heat pump swap is usually less per ton and simpler than 3–4 mini-split heads.
• Whole-home dust + filtration. A central system with a good MERV rating filter handles whole-home filtration in one pass. Mini-splits filter at each head, which is fine for cooling/heating but lighter on whole-home IAQ unless paired with a separate whole-house air purifier.
• You want one wall-mount unit per room hidden. Some owners dislike the visible mini-split head. Concealed-duct mini-split variants exist but bring back some of the install complexity central systems carry.
• Resale-priority homes. Most buyers expect central air. In a resale-focused tract home, central is the safer move.

Cost reality (rough range, verify with a real quote)

These are San Diego County rough ranges for installed cost, including permit, Title 24 paperwork, and basic electrical work. Real prices vary by home, brand tier, and tonnage:

• Single-zone mini-split (one head, one room): $4–7k
• Two- to three-zone mini-split system: $9–18k
• Full central AC retrofit with new ducts in a 1,500–2,000 sqft home: $15–28k
• Central heat pump swap onto existing ductwork: $11–22k

For homes between 1,200 and 2,500 sqft with no ductwork, a 2- or 3-zone mini-split is typically the better value. Above that, central starts to win on cost-per-room.

The hybrid case

Sometimes the right answer is both. A small central system handling the public spaces + a single mini-split head in the primary bedroom for night-time temperature control. Or a central system in the main house and a mini-split in the ADU above the garage. We'll size and route per the Manual J load calculation and tell you straight if a hybrid solves comfort issues central alone won't.

Next step

If you already have a quote for either approach, get a free second opinion — sizing mistakes here cost real comfort and real money. If you're starting from zero, start with how heat pumps work, then the heat pump vs furnace comparison if you also need heating.