Yes to both, in most jurisdictions. A mini-split is heating/cooling equipment under the code, sized like any other equipment, and installing one is mechanical work plus an electrical circuit. Here is where the requirement comes from and what actually gets submitted.
Short answer: yes to both, in most jurisdictions. A ductless mini-split is heating/cooling equipment under IRC M1401.3, which requires sizing per ACCA Manual S from Manual J loads with no exemption for single-zone or "small" systems.1 IECC R403.7 repeats the same sizing requirement as a mandatory energy-code provision.2 And installing one is mechanical work - plus a new electrical circuit - that jurisdictions require a permit for, the same as a furnace or central air conditioner. The "it's just a little unit" instinct is understandable, but the code does not size equipment by how it looks on the wall.
Some homeowners assume a ductless system is closer to a window air conditioner - a plug-in appliance - than to a furnace. It isn't. A mini-split has an outdoor condensing unit, one or more indoor heads (evaporator/air-handling units), and refrigerant piping and electrical wiring connecting them, permanently installed and integrated into the building.4 That description matches how the code treats mechanical equipment generally, and building departments treat it accordingly: a state guidance document from Massachusetts walks through this reasoning directly, concluding that because a mini-split includes piping, controls, and other integrated components, it qualifies as equipment under the mechanical code and a permit is required.4 Nothing about being ductless, single-zone, or low-capacity changes that conclusion.
Usually both, and they're pulled separately. The mini-split itself - outdoor unit, indoor head, refrigerant line set, condensate line - is mechanical equipment and needs a mechanical permit. It also needs power: a dedicated circuit to the outdoor unit, which is electrical work requiring its own permit, typically pulled by a licensed electrician. A Massachusetts town's mini-split permitting guidance spells this out plainly for a standalone retrofit installation: a mechanical permit for the equipment, and "an Electrical Permit issued to a licensed Electrician."5
There's a third layer that isn't a permit at all but still controls who can touch the job: the refrigerant. Opening the sealed refrigerant circuit - adding gauges, adding or removing refrigerant, anything that could release it - requires the installer to hold EPA Section 608 technician certification under the Clean Air Act, regardless of what the local mechanical permit requires. It's a federal requirement, not a state or local one.6 A homeowner-installed mini-split kit that never has its refrigerant lines opened (a pre-charged, quick-connect system) sidesteps this; a standard split system with field-brazed or flared line sets does not.
It varies, and this is one of the areas where local rules diverge the most. Owner-occupant exemptions that let a homeowner pull a permit on their own primary residence are common across states and cities. But that exemption is about who applies for the permit, not about who is legally allowed to do the licensed trade work. Electrical work generally still needs a licensed electrician even on an owner-pulled permit, and refrigerant handling still needs an EPA 608-certified technician no matter whose name is on the paperwork. Some jurisdictions also distinguish a construction supervisor's license (needed if the installation involves cutting or notching structural elements) from the basic equipment installation itself, which may not require it.5 None of this is uniform enough to state as a blanket rule - check your state's page for how your jurisdiction handles owner-pulled permits before assuming you can do the whole job yourself.
Central systems get load-calculated more consistently than mini-splits do, and the reason is mostly habit, not code. A central furnace or air conditioner sizing conversation has been part of the permit package for decades in many markets; a mini-split retrofit often gets sold and installed as a smaller add-on - "you need about a 12,000 BTU unit for a room that size" - without anyone running the numbers. IRC M1401.3 doesn't distinguish: heating and cooling equipment is sized per Manual S based on Manual J loads, full stop, with no carve-out for ductless or single-zone equipment.1
What goes wrong when sizing is guessed rather than calculated is specific to how mini-splits operate. Most ductless heat pumps use an inverter-driven compressor that modulates output rather than cycling fully on and off, and most can only turn capacity down to roughly 30 percent of the unit's rated output - they can't run any lower than that floor.3 If a room's actual load sits well below that 30 percent floor - which is exactly what happens when a unit gets oversized because someone rounded up "to be safe" - the compressor can't idle down far enough to match the room. It short-cycles: on, briefly satisfied, off, on again. Short-cycling wastes energy, wears out the compressor faster, and means the unit never runs long enough in a cycle to pull humidity out of the air - the room ends up cold and clammy at once. A room-level load calculation, matched against the equipment's actual modulation range, is what avoids that gap. A guess sized "generously" is the most common way to end up in it.
Requirements vary by department, but the pieces a plan reviewer typically wants on a mini-split mechanical permit are the same categories used for any equipment permit review: equipment type, size, and efficiency; the equipment and system controls; and the location and installation of both the indoor and outdoor units.3 In practice that means:
Field inspection tends to check the same list plus the physical details: refrigerant piping insulated to the approved R-value, the outdoor unit's access ports capped to prevent tampering, and the condensate path actually built the way the permit said it would be.3
A single-zone mini-split is one outdoor unit connected to one indoor head, serving one room or open area. The Manual J for it is a load calculation for that specific space, and the Manual S selection matches one piece of equipment to one load - about as direct as equipment sizing gets.
A multi-zone system connects several indoor heads to a single outdoor condensing unit, each head on its own refrigerant branch serving its own zone with its own thermostat.3 The underlying requirement doesn't change - each zone still needs its own room-level Manual J - but there's an added check: the shared outdoor unit's total capacity has to cover the combined load of every head running on it, not just satisfy each room in isolation. Undersize the outdoor unit relative to the sum of the zones and every head suffers on a peak day, even though each individual room's number looked fine on its own.
On a central ducted system, one blower and one set of ducts serve the whole house; the Manual J is still done room by room, but the duct system distributes that capacity across rooms, imperfectly but adjustably, via duct sizing and dampers. A mini-split removes that layer. Each head is its own zone with no distribution system correcting for a bad room-level estimate - if the load calculation for that room is off, the head serving it is the wrong size for that room specifically, not just for the house in aggregate.3 A whole-house average or a per-square-foot shortcut is a worse fit for mini-splits than it already is for central equipment: there's no ductwork downstream to absorb the error.
Free online mini-split sizing tools that ask for a room's square footage and hand back a BTU number are common, and they market themselves as a faster, cheaper stand-in for a load calculation. They aren't one, and the gap isn't about accuracy at the margins - it's about what inputs the calculation uses at all. A square-footage rule of thumb can't account for how many windows a room has, which direction they face, how much insulation is behind the walls, or how much air leaks in around the framing - the variables a Manual J is built to weigh room by room. Two rooms of identical square footage, one with a west-facing wall of glass and one windowless, do not have the same cooling load, and a calculator that only asks for square feet cannot tell them apart.
That's also why it doesn't satisfy the code. IRC M1401.3 requires loads "calculated in accordance with ACCA Manual J or other approved heating and cooling calculation methodologies" - a rule-of-thumb square-footage estimate is not an approved methodology, it's a shortcut that produces a number in the same units.1 A plan reviewer checking a mini-split permit is looking for a load calculation that traces back to the room's actual construction, not a number that could have come from the square footage alone. If your Manual J and your floor plan's window schedule tell the same story, that's the difference a reviewer is checking for.
For a mini-split's Manual J, send the floor plan or room dimensions for the zone (or zones) the system serves, the window schedule for that area, and the equipment you're considering if you already have a model in mind - we'll size to it or tell you what capacity range fits. Manual J is $249 for up to 3,000 square feet; Manual S equipment selection is a $50 add-on to that order (ask when you order). If the same project also needs an energy code compliance report for new or altered envelope area, the Manual J + REScheck package covers both.
Related reading: Do I need a Manual J? covers when the code requires a load calculation across project types generally, and does a heat pump change-out need a Manual J? covers the ducted-heat-pump version of this same question.
Usually both. The mini-split itself needs a mechanical permit; the new dedicated circuit needs a separate electrical permit pulled by a licensed electrician. Opening the refrigerant line set additionally requires EPA 608 technician certification, apart from either permit.
It varies by jurisdiction. Owner-occupant exemptions for pulling the permit are common, but they don't usually extend to who can perform the licensed electrical or refrigerant work. Check your state's page before assuming you can do it all.
No. IRC M1401.3 requires a load calculation under Manual J or another approved methodology, with no exemption for ductless or single-zone equipment. A square-footage rule of thumb isn't an approved methodology.
Usually oversizing. A mini-split's compressor can only modulate down to about 30 percent of rated capacity; below that floor it short-cycles, which hurts both efficiency and humidity control.
Typically the equipment cut sheet, the Manual J and Manual S, the unit locations, the condensate path, and the electrical circuit details for the separate electrical permit.
Same underlying requirement - Manual J per room, Manual S selection - but a multi-zone system also needs the shared outdoor unit's capacity checked against the combined load of every head on it.
Permit categories, owner-pull rules, and licensing thresholds (like the construction-supervisor example above) are set locally and vary by state and city; the Massachusetts example illustrates how one state works through the question, not a rule that applies everywhere. Use the state finder for your jurisdiction's specifics, and confirm current permit requirements with your local building department. Final authority rests with your building official.
Travis Smith, ICC-Certified Residential Energy Inspector / Plans Examiner. The same certification your building department's plan reviewer holds - working for you.