This Texas school has two conventional buildings, each with 20 air conditioning units along its back wall. That’s 40 units for just one tax-supported school! What does it cost to install and run 40 ac units in hot, humid Texas? Also, consider that this is a school for less than 300 students. Cost to cool your building It depicts the back side of one of two buildings that function as a traditional Texas school serving 236 students in Kindergarten through Grade 12. Like many traditional schools, this building has a line of 20 air conditioning units along its back wall. The companion building has another 20 units along its back wall. That’s 40 AC units at just one school! Consider what it costs to install 20 units. How much electrical do those 20 units require? How much just plain expense does it take to install and run 20 units? And these units are not inexpensive toys. They are not $100 window units. By the time the unit is installed, each costs a minimum of $3,000 to $4,000.

And bigger units cost two to four times that much. The next time you drive through town, please think about this. central ac units how they workLook at the schools, look at the churches and just do a rough count of the AC units you see. 2 ac units better than 1Keep in mind that most schools and churches hide their units along the building’s back side.how to size your ac unit As I drive through the suburbs of Dallas, I’m constantly stunned by the number of AC units I see at schools. Many have one major AC unit for each classroom. That costs serious money – not only to install but to hook up, to maintain, to replace and most of all to furnish with power. It’s no wonder that we receive so much acclamation for our Monolithic Domes.

Our domes use one fourth that amount of air conditioning. Most conventional churches and schools in Texas use one ton of air conditioning for each 250 square feet. The rule of thumb for a Monolithic church or school is one ton of air conditioning for each 1,000 square feet. That’s 1/4 as much! It takes a lot of money to heat and cool buildings such as the one pictured here – especially to cool them in Texas where, in some years, we have more than 100 days of 100 plus degrees.Turning your whole house into an integrated, mean-lean-cooling-and-heating machine is the ultimate in weather-defying comfort - cool air for the kids playing Wii tennis in the TV room, something a little balmier for after-dinner yarns in the living area, a cosy warmth welcoming you to bed... But the cost, effort and disruption involved means ducted AC installation is not to be taken on lightly, and you really have to do your research! Looking for the best air conditioner? See our expert product reviews.

Is it worth the cash? Before you spend thousands of dollars to have a system installed (and several hundred dollars a year to run it), consider other cooling and heating options to make sure it's worth it. Even if you decide on a central system, you may only need a cooling-only or heating-only model (depending on the climate where you live). And, as with all our heating and cooling guides, we strongly advise you to optimise your home's energy efficiency before diving into this process. For info on ways to do this, including tips on insulation and draught-proofing, check out our comprehensive guide. Where's the CHOICE test of ducted systems? If you decide to install a central system, the right size and design depend on a range of parameters and have to be determined by the supplier for your individual situation. Central systems shouldn't be bought "off-the-shelf" – which is why we don't test ducted systems. The results would only be valid for the tested scenario (which could be very different from your house) and a model that performs well in our test situation can still disappoint you if it's not designed according to your needs.

So what does 'reverse cycle' actually mean? Air conditioners work on the heat pump principle. As the name suggests, they pump heat from one place to another. Allow us to get a little scientific here, as we explain how heat pumps work A fan draws hot air from your home over a cold liquid, called a refrigerant. Heat is absorbed from the air, cooling it. The air then flows back into your home. The refrigerant, warmed from the hot air, evaporates and flows into a compressor, which creates a high-pressure, high temperature gas. The gas is pumped through a heat exchanger outside your home, which allows heat to escape and the refrigerant to cool and liquefy again. The refrigerant flows through an expansion device that lowers its pressure, cooling it further, so it can absorb heat again. Reverse-cycle air conditioners, as the name suggests, can reverse this process and be used for both cooling and heating. If you're looking to put a brand new ducted system in an existing house (as opposed to incorporating it into a new build), you'll need to take into account a whole lot of details about the structure, inside and out.

You should have all of the following info before you start shopping around for quotes or designs: Your home's floor plan: How many levels are there? What are the dimensions of the rooms (including ceiling height)? Which direction do the rooms face? The size, position and orientation of windows and doors. The type of construction (for example, weatherboard or full brick). The level of insulation. The number of people living in your home. The main use of each area (for example, sleeping, living, cooking). The ceiling cavity space - slimline systems are available for homes with small ceiling spaces. The limitations of your outdoor spaces - just as with split system air conditioners, the outdoor compressor unit(s) needs to be installed somewhere where noise won't be an issue (for you or your neighbours!). Large systems may require a three-phase power supply, which will be an extra installation cost if you don't already have it. There are several design features to consider.

A supplier may be able to offer a range of options, depending on the design and requirements of your home. Vents come in a variety of designs and can be installed in the ceiling or walls. Controls are usually hard-wired and mounted on a wall, unlike the remote controls used for single split-systems. You may have one controller for the entire system, but in a large house you might opt for extra controllers in other parts of the house for more convenience. Sensors are used by the controller to keep the room at the targeted temperature. Large open-plan areas may need multiple sensors. Most systems allow for a home to be divided into zones for convenience and economy, so that you can turn on the air-con for only the part of the house you want cooled or heated (for example, living areas during the day and bedrooms after 10pm, or different floors) rather than the whole house. Or, you can set different climate levels for different areas as required. The ducting is a key component of the system.

Ducts need to be thermally efficient so that valuable cooling or heating isn't lost travelling between the air conditioner unit and the target room. The ducting industry association, ADMA, is concerned that some suppliers are installing inferior ducting, and recommends that consumers check with their installer that the ducting meets the Australian standard for ductwork, AS 4254. Check the labels on the ducts or get a written statement of compliance to make sure you get the right quality of ducting. Are they energy efficient? Modern air conditioners are very efficient - for every kW of electricity consumed, three or more kW of heating or cooling capacity can be produced. Window and split-system models must carry an energy rating label (the star-rating system). Ducted systems have to meet minimum energy performance requirements, but don't carry the energy rating label. See the government's energy rating website for more info. How much will it cost to buy and run? You'll be hard-pressed to purchase a ducted reverse-cycle air conditioning system for less than $5000 (including installation), and the cost can easily reach twice that amount (or more), depending on the size and type of system you choose.

The running costs mainly depend on: The type and size of your system The energy efficiency of your system The time you're operating the system for The construction of your home (floor plan, level of insulation, size of windows, etc.) The electricity tariff you're paying The temperature you choose on the thermostat: each degree Celsius lower/cooler you set it to in summer, and each degree higher/warmer in winter, will increase the running costs by 10-15%. We know it's tempting to fight Mother Nature by blasting it, especially when you've just come in from outside feeling fried or frostbitten, but the best thing to do is to find the temperature you're just comfortable with – try 25 degrees in summer, and 20 degrees in winter. By following some easy rules in day-to-day operation, you can further reduce running costs: Close all external windows and doors when your system is running. Shade your windows during hot summer days (to keep the heat out) and during cold nights (to keep the heat in).