Often a single ductless mini-split will fit a 100-amp service that would struggle with a central heat pump and a large strip kit, but “often” is not a calculation. Many single-zone outdoor units are on a 15-amp or 20-amp 240-volt circuit. That is a real load, just not a 40-amp EV-shaped load. Several outdoor units, a central air handler with strips, or a charger on the same 100-amp panel can change the answer. The nameplate and the circuit rating have to go on the load sheet.
Educational optional-method walk-through: the same 1,800 ft² all-gas example, no charger, with a labeled 3,600 VA heating and cooling nameplate (15 A at 240 V — a stand-in, not a typical product).
| Step (2023-style optional method, educational) | Result |
|---|---|
| General lighting at 3 VA/ft² | 5,400 VA |
| Small-appliance and laundry circuits at 1,500 VA each | 4,500 VA |
| General load including listed nameplates and EVSE | 9,900 VA |
| First 10 kVA at 100%, remainder at 40% | 9,900 VA |
| Larger of the heating or cooling values entered, at 100% | 3,600 VA |
| Calculated load | 13,500 VA · 56.2 A at 240 V |
| Compared with this walk-through’s service rating | 56.2 A is under a 100 A rating by 43.8 A |
Educational walk-through of the optional dwelling-unit method structure in NEC 2023 220.82. Not a permit calculation. 220.82(C) heating/cooling selections can be more involved than “the larger of two numbers,” especially with heat-pump backup strips.
That walk-through is about 56.2 A, comfortable on 100 A in this light house. Adding a 32 A charger as well is about 69.3 A, still under here, and closer to the tighter EV examples if you also have an electric range. Use your outdoor-unit MCA and MOCP from the data plate, not 3,600 VA, and run the panel calculator. If the mini-split is the only heat in a cold climate, that is a capacity-at-5°F question as well as a panel question.
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.