AIR-TO-AIR (A2A) MINI-SPLIT HEAT PUMPS

  • Heating and Cooling only. No hot water production.

  • Refrigerant lines are run from outdoor unit to indoor heat distributors (e.g. “split”); this limits their application and requires specific HVAC expertise.

  • Very common and many HVAC contractors install them

  • Cost: $5,000 to $15,000+ installed before any tax credits.

  • January 2025 Update: There are a wide array of very efficient and very low cost (FYI Chinese-made) mini-splits available online that are DIY friendly for between $1,000 to $2,000. Be sure to specify low temp (e.g. -15F) operation (“hyper-heat”) and highest possible efficiency ratings (“SEER” ratings between 20-27).

WHAT DOES “SPLIT” MEAN?

It means the system has a “split” configuration: that is, an OUTDOOR unit and INDOOR unit (with small refrigerant lines connecting them)

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  • Best for smaller spaces (like an accessory dwelling unit (ADU) or to supplement heating of bigger spaces (e.g. colder rooms of a larger home or an office or great room).

    They can be tied to duct work/forced air systems but many contractors who do this type of system in the Bozeman area use heat pumps that require gas backup furnace heat to kick in at 30-40F; so the heat pump energy usage savings are minimized. Contact us for more info and we can refer to specific contractors.

    Mini-splits may also used in very well-insulated homes like passive-houses with an open floor plan and limited square footage.

  • Trick Question. As of 2025 we do not install mini-splits.  But we can recommend installers in the Bozeman area.  Brands we like include Fujitsu, Mitsubishi and Daiken.

    For off-grid homes there are some interesting DC-direct cooling-only mini-splits that connect directly to solar panels and a small battery bank.

  • Mini-splits are rated as low -15F depending on the brand and model. In cold climates like Montana some type of backup heating is required (e.g. electric “cove” heaters are our favorite choice). In warmer climates like the western Oregon and Washington no backup is generally required.

  • The best mini-splits are very efficient. A high efficiency model, such as Fujitsu Hyper-Heat (that can function to below zero temps) would consume (very) approximately 2,000-2,500 kilowatt hours (kwh) or 2 to 2.5 kilowatts (kW) in a 1,000 SF well-insulated apartment located in our Bozeman climate.

Diagram of a ductless mini-split air conditioning system showing an air handler/evaporator inside a room connected via conduit to an outdoor condenser unit next to a tree.

MINI-SPLIT ILLUSTRATION

Mini-splits consist of two main components: 1. the outdoor mounted heat pump (typically wall mounted); and 2. at the indoor emitter (or handler/evaporator). In addition there are small diameter copper refrigerant lines (wrapped in insulation and conduit), and a power supply to the outdoor unit.

HYPER-HEAT OUTDOOR UNIT

Outdoor air conditioning unit mounted on a house exterior wall.

A Fujitsu Hyper-Heat outdoor unit ; is rated to -15F

On the right is the electrical disconnect box (usually tied to a 20 amp breaker) and on the left are the insulated refrigerant lines that go to the indoor unit.

There are MANY brands, models, and levels of quality and performance. So choose the most efficient (a high “SEER” rating).

As of 2025 request a mini split with R32a refrigerant (better performance and refrigerant has much lower greenhouse gas impact should the refrigerant ever leak).

INDOOR EMITTER

Wall-mounted air conditioner on a wooden bracket

The indoor emitter (that gently blows warm or cool air). Pic above shows it trimmed out nicely.

Some mini-splits can accommodate three emitters but a single is most common

These emitters use a hand-held remote as a thermostat.