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Mini Split vs. Window Unit

Since they were first developed by Mitsubishi Electric in Japan over 30 years ago to accommodate the growing need for air conditioning in smaller Japanese residences, ductless mini split technology has expanded to become the most common AC installed in Asia and Europe. Now these highly efficient units are being installed across the United States as well. The mini split is replacing window units and often competes favorably with central air by offering a set of advantages that overcome many of the drawbacks of other more established systems.

About Mini Split Systems

Ductless mini splits consist of a compact indoor air handler mounted on a wall or ceiling in a single room. This unit incorporates an indoor coil and a fan to quietly circulate cool air into the room. The unit is operated by a wireless remote with controls for programming temperature, fan speed and shifting from cooling mode to heating mode. The indoor air handler is linked to an outdoor heat pump unit located behind or to the side of the home. This downsized cabinet contains an outdoor coil and fan as well as the compressor. Refrigerant circulates between the indoor and outdoor components via copper tubing in an insulated conduit. A three-inch diameter access hole in an exterior wall for the conduit is the only external opening required to install the ductless unit.

A mini split operates like a high-efficiency heat pump. In summer, the indoor coil extracts heat energy from household air drawn over the coil by the blower fan. The heat is absorbed by the refrigerant circulating through the coil and conveyed to the exterior unit, where it is dispersed into the air by the outdoor coil and fan. During winter, newer models of mini splits also incorporate the heating function that extracts latent heat from the outdoor air, concentrates the heat molecules in the refrigerant in the compressor cycle, then carries it indoors where the coil and fan in the air handler disperse the heat into the room.

The mini split shines in applications in which cooling a single room or other enclosed space in a home is desired. Many older homes simply cannot be retrofitted to accept the ductwork necessary for installing central air or else the complex process would not be feasible financially. When considering how much mini split systems cost, the savings on ductwork and monthly utility bills must be figured into the equation. In residences with existing central air, expanding the duct system into a new addition—which may in turn necessitate upgrading the entire central unit to provide additional cooling capacity—is an expensive and major construction project. For these scenarios, a ductless system is made to order.

Ductless Mini Splits Beat Out Window AC Units

Most frequently a ductless mini split is considered as a viable alternative to installing a conventional window air conditioner. Although window unit air conditioning does have some points in its favor—mostly low cost and DIY installation—there are a number of factors that make ductless technology a preferred option when compared to window-mounted AC units.

  1. Ductless mini splits are far more efficient than window units. In most cases, they will use almost one-third less electricity to produce the same comfort level as a portable air conditioner installed in a window. Because energy efficient technology takes up space, most window units don’t have enough room to incorporate components that add extra efficiency. For example, the latest model ductless mini splits utilize variable output compressors that constantly adjust compressor output to match the cooling load for the most energy-saving operation. Window units incorporate single-speed compressors that run at full blast all the time, even when the cooling demands don’t require it.
  2. Window units are notorious for the high decibel levels of sound they generate. This is because the noisiest components, particularly the compressor, are installed in the unit itself, only a few feet from where occupants of the room are located. In a ductless mini split system, the compressor and condenser fan are outdoors and enclosed in a noise dampening cabinet. Also, the multi-speed oscillating fan incorporated in the indoor air handler of ductless units moves air almost noiselessly compared to the conventional blower in a window AC units.
  3. When faced with the choice of mini split or window unit, aesthetics is another issue that favors ductless mini splits. Once installed, window air conditioners occupy a significant portion of a window in a room. This not only obstructs your view of the outdoors, it also blocks the level of healthy natural light entering the room and requires more use of electric lighting.
  4. Many homeowners are also concerned about safety. A window unit installed in a half-open window can be an invitation to burglars. Pulling a window unit out of its mount is often easier than forcing open a door or opening a closed and locked window elsewhere in the house. Once the window unit is out of the window, intruders gain easy access to your home and possessions.