Both ductless mini-splits and central AC effectively cool homes, but they suit different situations. Here is how to decide.
How They Differ
Central AC cools your entire home through ductwork. An outdoor condenser connects to an indoor evaporator coil in the air handler. Cooled air distributes through supply ducts to every room.
Ductless mini-splits cool individual zones without ductwork. An outdoor compressor connects to one or more indoor units via small refrigerant lines. Each indoor unit serves its zone independently.
When Central AC Makes Sense
Existing ductwork: If you have ductwork in good condition, central AC uses it efficiently.
Whole-house cooling: Central systems treat the entire home uniformly from one thermostat.
Lower upfront cost: For homes with ducts, central AC typically costs less to install.
Invisible operation: All equipment except vents is out of sight.
When Mini-Splits Make Sense
No ductwork: Victorian homes, additions, and conversions often lack ducts. Mini-splits avoid the cost and disruption of adding them.
Zoning needs: Multi-zone mini-splits let you control each area independently, avoiding cooling unused spaces.
Supplemental cooling: Mini-splits can address problem areas without modifying the main system.
Efficiency priority: Ductless systems eliminate duct losses (20-30% of cooled air in typical homes).
Tight spaces: Mini-splits require only small line penetrations versus extensive ductwork.
Efficiency Comparison
Mini-splits are inherently more efficient due to: - No duct losses - Variable-speed operation - Zoned control reducing unnecessary cooling
Central AC efficiency has improved but duct losses remain a factor, especially for ducts in unconditioned spaces.
Installation Considerations
Central AC requires existing ductwork or space to install it. Installation takes 1-3 days typically.
Mini-splits require outdoor unit placement and indoor unit mounting. Multi-zone installations take 1-2 days per zone.
Both require electrical capacity. Mini-splits may need less total capacity if zoning reduces peak demand.
Aesthetics
Central AC: Indoor components are hidden. Only vents and thermostat are visible.
Mini-splits: Indoor units are visible wall or ceiling-mounted rectangles. Placement affects aesthetics.
Some homeowners find mini-split units intrusive; others accept them for the benefits.
Operating Differences
Central AC treats the whole house as one zone. Temperature varies based on thermostat location.
Mini-splits maintain temperature precisely in each zone. Different zones can have different temperatures.
Bay Area Considerations
Fog belt: Mini-splits may be perfect for occasional cooling needs without full central system investment.
Victorian homes: Mini-splits avoid ductwork challenges in historic structures.
Additions and ADUs: Mini-splits serve new spaces without extending central systems.
High-efficiency needs: Mini-splits maximize efficiency in our moderate climate.
Making the Decision
Consider: - Do you have existing ductwork in good condition? - Do you need whole-house cooling or targeted zones? - Is equipment visibility acceptable? - What is your budget for upfront and operating costs?
Many Bay Area homes benefit from mini-splits, especially those without ducts or wanting zone control. Central AC remains efficient for ducted homes wanting uniform whole-house cooling.