The HVAC system represents up to 39% of office and 48% of residential energy usage. So saving energy should be top-of-mind as you select the best system for your cooling (and heating) needs. Here are some A/C options to help guide you:

  1. Window-mounted/mobile/portable A/C needs access to a partially open window where a plastic panel is inserted and a flexible duct penetrates it to pull in outdoor air to be cooled. The advantages are it’s the most affordable and easiest to install, there’s no design or install needed from an outside party, and it plugs into your standard wall outlet/receptacle (no electrician needed to upgrade your wiring for more electrical power). The disadvantages are it takes up window and floor space, vents/exhausts some warm air back into your room (less efficient), and it can be very noisy. Toshiba RAC-PD0811CRU.
  2. Wall-mounted (ductless)/ through-the-wall A/C is mounted inside a sleeve that has been installed in a space cut into an exterior wall, generally underneath a window.
  3. Packaged terminal A/C (PTAC) is the same as wall-mounted, but most combine heating and cooling in one unit. They are usually hooked up to a building’s hot-water system. Hot water produced by the boiler flows into the unit, and circulates the resulting radiative heat into the apartment. It has a separate chamber containing coolant that produces cool air.
  4. Mini-split (ductless ) A/C [a type of split system that’s not central air (ducted)] has a wall-mounted indoor unit(s) and an outdoor unit placed nearby on a concrete pad.

The indoor unit is the evaporator and evaporator coil “cold coil” filled with refrigerant. The outdoor unit is the compressor, condenser, condenser coil “warm coil”, and fan. If heating is desired the condenser is referred to as a heat pump which can heat and cool (often A/C is combined with a furnace for heat). Indoor unit: LG LSN090HFV3 and outdoor unit: LG LMU30CHV


1. brickunderground.com/blog/2013/07/go_a_through_the_wall_or_ptac_ac_system_were_here_to_help

2. ptacs.com/window-ac-vs-ptac