Existing ducts tilt the comparison toward a central, ducted heat pump — if those ducts are worth keeping. A ducted unit can use the present air handler closet, the present thermostat locations, and the present room-to-room layout, and it keeps filtration and a single outdoor unit in a familiar place. Ductless mini-splits avoid the ducts entirely: they are often more efficient as machines, they zone well, and they make sense in a house whose ducts are in a hot attic, are undersized, or never reached an addition. They also put indoor heads on the walls and require a refrigerant-rated install at each zone.
Have the ducts evaluated, not assumed. Leakage, insulation, and static pressure can erase the theoretical efficiency of a new central heat pump, and they can also be repaired. A hybrid — a central ducted unit for the main house plus a ductless head for a bonus room — is a legitimate design, not a compromise you have to apologize for.
Sizing is Manual J in either case; see the mini-split sizing pages and the 2,000-square-foot caution page. Operating cost still goes through HSPF2 or a COP and your rates in the calculator. The panel question is usually kinder for a ductless head than for a central unit with large backup strips, but both need a load calculation — see the 100-amp mini-split page.
This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.