Is a heat pump the same as an air conditioner?

This is a guest post contributed by a retired HVAC technician who now does training and educating on the subject.  Make sure to check out the links at the end of the article.

You might be interested in learning about air conditioners, but not know where to start. Perhaps you want to get a new one for your property or want to upgrade from the one you currently have. In either case, don’t worry because this article will provide all the answers to any basic questions you may have about ACs.

Aren’t all AC Units the Same?

It turns out, not all air conditioners are the same.

Some are suitable for small apartments, some for detached houses and some for commercial and office spaces. A mall’s air conditioning system, for example, will be much larger and consume more power than that of a house. And even though it works according to the same basic principles, it may use a very different system for delivering the cool air.

You will, of course, choose an AC that fits your budget, but you should know your AC terminology when you go shopping for units. AC sizes are measured in BTUs or Tons (12000 BTUs = 1 Ton) and they are given SEER ratings for efficiency. The higher the SEER number, the more efficient the unit.

Depending on the kind of rental property you have and the location where you live, you’ll require a different type of AC. Air conditioners come in several different types that we’ll discuss in more detail below.

Central Air

Central air conditioning systems use a condensing unit, which is usually in the form of a large metal box outside the home. The condensing unit, which houses the compressor, condensing coils, and condensing fan, is connected to the evaporative unit inside the home with a refrigerant tubing line. The evaporative unit contains an evaporator coil and an expansion valve. The treated air gets moved through the home in a series of ducts, most often the same ducts connected to the furnace or heating system. Systems will cycle on and off as the interior temperature needs to be adjusted.

Central air conditioning systems are usually recommended for warm climates. One of the benefits of choosing central ACs is that they provide the most consistently comfortable climate with the best performing and quietest system available.

You might run into some contractors or sites that try to sell you on a “rule of thumb” guide to how big a system you need. Often they say one ton of air conditioning for every 500 square feet. But this method is seriously lacking. A competent contractor is going to calculate according to “Manual J”, which is a guide for determining the right amount of AC. It takes into account climate, average temperature, the direction your house faces, how many windows there are, and other factors. So there’s no easy way to guess-timate based on just square footage.

Think bigger is better? Not here. AC units work on two basic principles: blow in cool air and dehumidify. An AC unit that’s too big will cool the air too fast and then shut down before it can dehumidify. So you’re left with a room that’s cooler but really humid and even musty.

The cost of a 3-ton central AC system with a SEER (Seasonal Energy Efficiency Rating) of 18 for a 2,400 square foot area in Los Angeles, California, would be around $3,904.56 on the low end around $4,825.80 on the high end.

Installing ductwork for central ACs can be expensive. The ductwork is prone to leaking when damaged or due to deterioration from age. The ductwork may need to be updated or modified if you’re replacing or upgrading a current system to ensure it is compliant with the new system. For a new installation, you must factor in the cost of the ductwork and labor. Some more modern systems let you have some control of where air flows so that each room can reach the right temperature, but central air doesn’t do this as well as a ductless system.

What is a Ductless Split System?

A ductless split system air conditioner consists of an indoor and an outdoor unit. It’s a great solution for quiet, convenient cooling to specific rooms or zones of your home.  The outdoor unit contains the condenser, compressor, and expansion valve. The indoor unit has the evaporator and cooling fans to blow air into the room.  Insulated conduits move the refrigerant and exhaust air between the indoor and outdoor elements.

The benefit of split ACs is that they are ductless systems which save money on the installation of a network of ductwork throughout the ceiling. Another option is a slim duct line ductless system, which uses minimal ductwork.

Since each AC unit is individually regulated, you can turn off units with a remote in rooms that do not need heating or cooling. Another advantage of ductless systems is that they have high SEER and HSPF (Heating Seasonal Performance Factor), which are measures the efficiency of the heat pump. Systems are available with 12,000, 18,000, 24,000, 30,000, 36,000, 42,000 and 48,000 BTUs.

A Multi-Zone (5 boxes) with 36,000 BTUs is estimated to cover 2,000 square feet. For homes or businesses with more square footage of 2,400 square feet, the addition of a single 12,000 BTU system with an inverter box may be necessary.

Ductless systems are available from many manufacturers. Depending on the size needed, units can range in price for $650 to $6,500 at current prices. Split units must be professionally installed due to wiring and refrigerant requirements.

Split units are recommended for properties where efficient and quiet cooling for multiple separate rooms is required. It’s a good option for a multi-family dwelling or something like studio apartments, as split systems are great for single rooms. That’s why they’re so popular in hotels, as well.

How Do Heat Pump Systems Work

Air heat pumps utilize a mechanical-compression cycle refrigeration system that can be used to either heat or cool a space. It will typically consist of two parts: an indoor unit called an air handler and an outdoor unit similar to a central air conditioner, but referred to as a heat pump. A compressor circulates refrigerant that absorbs and releases heat as it travels between the indoor and outdoor units. When it’s cold outside a heat pump extracts the outside heat and transfers it inside. When it’s warm outside, it reverses directions and acts like an air conditioner, removing heat from your home.

There are two types of air heat pumps. Air-to-water systems distribute heat by pumping liquid through pipes and radiators, or underfloor heating pipes.  Air-to-air systems produce warm air which is circulated around your home by a network of fans.

If installing the system in your home, you may want the heat pump installed at the side or at the back, as they’re large and unattractive. A sunny spot is best, so that the pump doesn’t have to work so hard to warm up the air in winter. However, it can even absorb heat from the air at sub-zero temperatures, so even a very small and shady backyard would do fine.

The pump works most effectively at lower temperatures, so they’re best with large radiators or underfloor heating. They provide a lower heat than conventional systems, so they will work best if your home is very well insulated. They aren’t suitable for apartments with no outside space for the unit. The average cost to install a heat pump ranges from $3,991 and $6,887 depending on the size of your home and type of heat pump, with low-end prices around $1,500 and high-end around $9800.

Portable and Window Units

A portable air conditioner is a mobile, self-contained unit that generally sits on the floor inside of the home.  The unit pushes cool air out the front, and releases exhaust heat through a hose vent that is secured to the outdoors through a window or opening in an exterior wall. Generally, portable air conditioning units are designed for single rooms under 500 square feet.

Portable units have the advantage of being able to be moved around as required. By removing the drainage tube and window kit, a portable model can be rolled around on its casters.

A window air conditioner is a self-contained air conditioning unit. It can be fitted into your home’s windows and blows cool air out of the front of the unit into a room and expels the hot air through the back. They are generally designed to cool a single room.

Window units come in a variety of sizes, they are affordable, and are relatively easy to install. On the other hand, as the unit is installed in either a window or in the wall, it is not as versatile as a portable unit. In addition, it cools the surrounding area faster than outlying areas. Window units provide the most cost-effective and painless solution to cooling a single room.

Portable ACs are usually owned by the tenant, not the landlord. Similarly, window units are also often tenant property. They’re generally not as efficient as more permanent options. They are also more intrusive. Window or through-the-wall units are, quite frankly, pretty ugly as well.


Whatever your property size, there’s definitely an AC type that’s the right fit for you. When considering what type to purchase, keep in mind the additional investment of ductwork and venting for central ACs, the mobility and convenience of portable ACs, and the efficiency ratings of the models you want. For smaller apartments, split ACs with high efficiencies may be suitable. But if you’re not able or willing to do a major upgrade and install central air, a heat pump or a split system, either you or your tenant will probably want to provide window units to help keep them cool and happy when the weather gets hot.


This is a guest post by Bob Wells, a retired HVAC tech who now dedicates himself to sharing knowledge on his website HVAC Training 101. Bob worked over 30 years in the field, 23 of which he ran his own contracting business. He’s dedicated to keeping up with the latest developments in the field and helping others to learn the trade better and advance their own careers.

Bob is on Twitter with the handle @hvactraining101 and you can also find him on Facebook.

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