Expert article on how to properly size a whole-house air conditioner for your home. Included are tips for reducing the load on your air conditioning unit. Manufacturers produce whole-house central air conditioners in a range of sizes, which raises one of the most important questions you’ll have to answer when shopping for one: How big should it be? With air conditioners, the term “size” has nothing to do with a unit’s physical dimensions but, rather, its ability to produce cooled air. Both room-size and whole-house air conditioners are manufactured in a variety of capacities, so it’s helpful to understand how they are measured. An air conditioner’s ability to produce cooled air is measured in BTU (British Thermal Unit) per hour and in tons. A BTU measures heat output. One BTU equals the amount of energy needed to raise 1 pound of water by 1 degree F. One ton is the equivalent of 12,000 BTUs per hour, or the amount of energy it takes to melt 1 ton of ice in a day.

For one thing, the larger the capacity, the more a unit will cost since output is directly related to cost. Also, it’s important to pick a size that is appropriate for your house. An air conditioner that is too small can’t keep up with load requirements on a particularly hot day. One that is too large will cycle off and on too frequently, doing a poor job of dehumidifying the air, which degrades comfort. In fact, it’s better to slightly undersize an air conditioner than to oversize it. Also, the air flow into and out of rooms must be carefully balanced to ensure efficient operation of the system. These factors, in addition to how well a house is insulated, how it’s used by your family, your climate, and more must be taken into account when selecting and designing your system. Though you should consult a qualified air-conditioning contractor before making any purchase, you can estimate your requirements by figuring you will need about 1 ton of capacity for every 400 square feet of living space in a marginally insulated house.

For example, a 2,000-square-foot house would normally require about a 5-ton air-conditioning system; air conditioner and heater unit for salea newer, well insulated house can often be served by a smaller system.can an ac unit run without a filter Featured Resource: Get a Pre-Screened Local Air Conditioning Contractorhvac air conditioner leaking water These simple measures will help you reduce your air-conditioning needs and save a bundle. When the weather gets hot, an air conditioner must work hard—that is, run frequently and for long periods—to keep a home at a comfortable temperature. Considering the energy cost of running an air conditioner, the net result of this is high utility bills. If you’re able to minimize the temperature in your home by other means, you can cut down on the work your air conditioner must do.

In fact, you can reduce the load on your central air-conditioning system by taking just a few simple measures. For starters, clean or replace your furnace or air handler’s filters. Clogged filters restrict the movement of air through the system, which reduces efficiency. Then consider the many improvements that can reduce your home’s heat gain such as utilizing heat-reflecting film on windows that face the sun, installing a foil radiant barrier in the attic, and improving your home’s insulation. Also to reduce heat gain you can simply pull shades or window coverings over sun-facing windows. Stir up breezes using a whole-house fan or ceiling fans, or circulate air using the “Fan Only” setting on the thermostat or equipment that controls your air handler’s blower. Also, when possible, minimize midday activities that add humidity to the air, such as washing clothes, showering, and cooking. Humidity makes the temperature feel warmer, and the air conditioner must work harder to remove humidity from the air.

If you would rather hire an air-conditioning pro to inspect and maintain your AC equipment, this FREE service will help you find a qualified local AC professional. For more helpful tips, see 9 Ways to Cool Your House for Less. Frigidaire 12,000-BTU 550-sq ft 115-Volt Window Air Conditioner Item # 530385 Model # FFRE12L3Q1 Room Size Cooling Capacity (Sq. Feet) Cools up to a 550 sq ft room Remote control allows you to precisely control the temperature and fan speed, from across the room Electronic controls allow you to set the comfort level to your preference, while a convenient temperature readout displays the set temperature Unit features 3 different fan speeds for more cooling flexibility Sleep mode: quiet operation keeps you cool without keeping you awake, and gradually increases room temperature after being activated Effortless restart means the unit automatically resumes operating at its previous settings when power is restored to your unit

Clean filter alert notifies you when your filter needs to be cleaned Optional side panels extend so you can adjust your unit to fit your window Cooling BTU Rating (BTU) Heating BTU Rating (BTU) Energy Efficiency Ratio (E.E.R.) Chassis for Slider/Casement WindowsEER (energy efficiency ratio): This heat pump efficiency value represents the cooling efficiency of an air conditioner or heat pump. This value is a single rated SEER (seasonal energy efficiency ratio): The SEER is just like the EER with one important exception. The SEER value is a more realistic heat pump efficiency measurement. The EER is measured using one set of temperatures at an Air Conditioning, Heating and Refrigeration Institute (AHRI) and U.S. Department of Energy required 95 F outside air temperature. The SEER is measured using the total cooling energy required for an average cooling season, divided by the total electrical energy required during that season.COP (coefficient of performance): The COP is a value that encompasses the purpose of the EER.

There are two main differences. First, COP can be used for both heating and cooling efficiency measurements. Second, the COP is dimensionless. In other words, the heating or cooling energy units (Btu/hr, W, etc) are converted to match the electrical energy units (Btu/hr, W, etc) before dividing the two into a ratio.HSPF (heating seasonal performance factor): The HSPF is the heating equivalent of the SEER. It is measured using the total heating energy required for an average heating season, divided by the total electrical energy required during that season. HSPF values are provided only for the heating portion of a heat pump. For the purposes of this website, the two values that will receive the most focus for heat pump efficiency are SEER and HSPF. These values are most accurate in defining expected energy usage over a given season.The approximate SEER can be calculated from the EER using the following formula: So what heat pump SEER/HSPF rating should you buy?It depends on a few factors.

Below are two tables that can give you some guidance if you are wondering  how what heat pump efficiency to purchase.In the first table below, locate your Zone Climate number based on the state and region that you live.If you live in Canada, your Zone Climate number is 1. Once you have located you Zone Climate number, go to the table below.  In this table you are given the annual cost per square foot for heating and cooling your home. Please note that these numbers are heat pump efficiency RULES OF THUMB.  There are many, many factors that go into how much it costs to heat and cool a home:However, below are average costs for an average home that could give you a little guidance as to what you can expect. Imagine that you live in Tennessee and would like to know how much money it would cost to heat and cool your 2000 sq. ft home for the year.  You are thinking about buying a heat pump but don't know what heat pump efficiency level you should purchase. Going to the first table, Tennessee is in Zone Climate number 3.Going to the second table, you retrieve the following $/sq. ft factors for Zone Climate 3:These are the approximate amount that one with a 2000 sq. ft home could spend in Tennessee per year on their heating and cooling costs.  

pare this to your existing cost for heating and cooling in your home.  If you currently have an old heat pump, for example 6 SEER/6 HSPF, compare the annual cost of using the above tables with your actual cost.This will help you to see if your new heat pump efficiency calculation is higher or lower than what is realistic for your home. Below is a table showing the SEER and HSPF of a number of residential and small commercial heat pumps on the market today. Energy star is a U.S. government program which encourages manufacturers to market their equipment with a high energy efficiency.The following are heat pump efficiency requirements for an Energy Star rating: The Tier 1 energy star compliance applies only toward equipment manufactured between April 1, 2006 and January 1, 2009. In order for equipment to be energy star compliant after January 1, 2009, the heat pump or air conditioner must comply with the Tier 2 values.Visit the U.S. Department of Energy for more heat pump efficiency information (as well as other heating and cooling energy data).