Buying a Central Air Conditioner How Central AC Works Central AC Problems & Repairs Central AC Cost & Installation Are multiple room air conditioners causing your electricity bills to skyrocket? Or, perhaps worse, is your house virtually unlivable during summer because of the heat and/or humidity? Maybe it’s time to consider central air conditioning. Central air conditioning, also called “central air” in the United States and “air-con” in the United Kingdom, is a system that cools more than one room in a house (in most cases, the entire structure). A conventional air-conditioning system blows cooled and/or dehumidified air through ductwork to deliver it throughout the interior spaces. In most cases, it employs an air handler (blower) and ductwork of a forced-air furnace for this cool-air delivery. A home air conditioner is an appliance that will have a huge impact on your quality of life and—depending upon how carefully you select one—your utility bills.

Running air conditioning can be expensive, so it pays to do your homework when choosing an AC unit. For example, it’s important to buy a unit that is large enough to cool your home but is not unnecessarily expensive or too large to operate efficiently. Cost, energy efficiency, capacity, and features are all covered in depth in the Central Air Conditioners Buying Guide. Air conditioners use refrigeration principles to cool the air. As discussed in How a Central Air Conditioner Works, a condenser, compressor, and evaporator work together to do this job. A typical split-system air conditioner has a compressor and condenser located outdoors and an evaporator unit mounted on the air handler or furnace. A package AC system combines all of these components in one outdoor unit. A central air unit draws room air through return-air ductwork, cools, dehumidifies, and filters it, and then blows it back into the rooms through air-supply ductwork. The AC unit is controlled by a thermostat, which turns the unit on and off as needed.

If your home has a central air conditioner that is not working properly, it pays to do some troubleshooting on your own before calling a professional to fix the problem. An air conditioner that doesn’t cool very well may just need a little basic maintenance. A unit that doesn’t turn on may just need to have a circuit breaker flipped. In many cases, the problem is with the thermostat, not the air conditioner. For a complete guide to troubleshooting and repairing air-conditioning problems, see Central Air Conditioner Repairs. Almost all central air conditioners are installed by professionals—the installation is quoted along with the cost of the equipment. Be aware that retrofitting an existing home with central air conditioning may be a difficult and expensive project. Ductwork must run from the air handler to the rooms and must usually be routed through the attic or under the floor. Small, relatively easy installations typically run well over $5,000; the only realistic way to get an idea of cost is to request free estimates from local air-conditioning companies (we suggest you get three bids).

If your home or your budget is not suited to this type of installation, buying one or more room air conditioners may be a better solution. air conditioning units high efficiencyFor more about room air conditioners, see Air Conditioners (Window & Room).ac power supply characteristicsOur expert guide to air source heat pumps shows you how air source heat pumps work, how much they cost, and how much they could save you on your energy bills.automotive hvac unitRead on to find out more about air source heat pumps, including their pros and cons.An air source heat pump (ASHP) is usually placed outdoors at the side or back of a property. It takes heat from the air and boosts it to a higher temperature using a heat pump. The pump needs electricity to run, but it should use less electrical energy than the heat it produces. 

Many air source heat pumps are eligible for payment through the Renewable Heat Incentive, a government scheme that provides payments to homeowners who generate their own heat. ASHPs are cheaper than ground source heat pumps. The Energy Saving Trust (EST) estimates that the cost of installing a typical ASHP system ranges between £7,000 and £11,000. The payback period (the time taken to recoup the cost of the system in energy savings) depends on how efficiently your system works, the type of system you're replacing, whether you can get money with the RHI and how you'll be using the heat generated from the pump. The EST says that an average performing air source heat pump in an average four-bedroom detached home could save:It also estimated that the RHI would pay an extra £905 to £1,365 a year.If you're considering installing an air source heat pump you can head to Which? Local to find an installer recommended by other Which? ASHPs look similar to air-conditioning units and are less disruptive to install than ground source heat pumps, as they do not require any digging in your garden. 

An ASHP works a bit like a refrigerator in reverse. The process consists of an evaporator, a compressor and a condenser. It absorbs heat from the outside air and the heat pump compressor then increases the temperature of that heat further to create useful heat.There are two main types of ASHP:In the summer, an air-to-air heat pump can be operated in reverse, like an air-conditioning unit, to provide cool air for your home.An air source heat pump system can help to lower your carbon footprint as it uses a renewable, natural source of heat – air. The amount of CO2 you'll save depends on the fuel you are replacing. For example, it will be higher if you are replacing electric heating rather than natural gas. Compare and switch suppliersChoose the fuel typeto compare:Gas and electricity Electricityonly Gas only A heat pump also requires a supplementary source of power, usually electricity, to power the heat pump, so there will still be some resulting CO2 emissions.Ground source heat pumps are also available.