Central air conditioning systems can last from 15 to 20 years. Sticking with an older unit may be less expensive in the short run, but not when it comes to helping you save money off monthly utility bills. Here’s some information to help you make a better decision when it comes time to get a new, energy-efficient central air conditioner. If you’re wondering whether it’s time to replace or upgrade your central air conditioning system, here are a few facts that might help: - In the average air-conditioned U.S. home, air conditioners use more than 2000 kilowatt-hours of electricity per year. - Producing the electricity needed to air condition the average U.S. home causes the average power plant to emit about 3500 pounds of carbon dioxide and 31 pounds of sulfur dioxide per year. - The most energy-efficient air conditioners on the market today consume 30 percent to 50 percent less energy than models manufactured in the mid 1970s. - Even if your air conditioner is just 10 years old, upgrading to a new energy-efficient air conditioner could save you from 20 percent to 40 percent off your cooling costs.

If you decide to replace or upgrade your central air conditioning system, the first thing you’ll need to know is whether you have a split-system central air conditioner or a packaged central air conditioner. Split-system central air conditioners are made up of an outdoor metal cabinet containing the condenser and compressor and an indoor cabinet containing the evaporator, which in many split-system air conditioners, also contains a furnace or the indoor part of a heat pump.my window ac unit is freezing up Packaged central air conditioners contain the evaporator, condenser and compressor in a single outdoor metal cabinet, usually placed on a concrete slab next to a home’s foundation. cost of commercial air conditioning unitFrom the cabinet, air supply and return ducts enter a home through its exterior wall and connect to a series of internal supply and return ducts in order to circulate cool air throughout a home. average ac unit replacement cost

Packaged air conditioners usually include a natural gas furnace or electric heating coils and eliminate the need for a separate indoor furnace. If your home already has a furnace but no air conditioner, then installing a split-system air conditioner is the most economical choice. When shopping for an energy-efficient central air conditioner, you’ll need to research a system’s seasonal energy efficiency ratio, or SEER, which indicates how much energy a model uses to produce a specific cooling output. If you have an older system, chances are it has a SEER rating of 6 or less. Since Jan. 23, 2006, models have been required by the Environmental Protection Agency to have a minimum SEER rating of 13, which require 30 percent less energy to run than models manufactured with the previous minimum SEER rating of 10. The most energy-efficient central air conditioners on the market today are ENERGY STAR–certified with SEER ratings greater than 13. Buying a new central air conditioning system doesn’t have to be intimidating.

Here are a few tips on what you should look for in a new system: - Size matters when it comes to a new central air conditioner. If your unit is too small, it will have to work too hard to cool your home, which can result in higher electric bills and damage to components. It may not even be able to reach comfortable temperatures on hot days. If your unit is too big, it will cycle on and off too quickly, which will prevent the unit from removing humidity from the air and can also damage components. Only a right-sized unit will provide the performance, operating life and energy efficiency you expect. Know your home’s square footage and consult with an HVAC contractor before you make a purchase. - Partial replacement may not be ideal. Although you can replace the outdoor compressor on an older model with a modern, high-efficiency unit, you should consult a local HVAC contractor to make sure that the compressor is properly matched to the rest of the older system. Even if it is, changes in refrigerants and air conditioning designs over the years usually mean it’s a wiser decision to replace the entire system.

- Look for an air conditioner with an EER rating of 11.6 or greater. An air conditioner’s EER rating is different from its SEER Rating. EER is an air conditioner’s thermal expansion valve and a high-temperature rating and determines how efficiently the unit runs when the weather is at its hottest. - Make sure the system runs quietly. - Look for systems that have a variable speed air handler for new ventilation systems, an automatic-delay fan switch that turns off the fan a few minutes after the compressor turns off and a fan-only switch so you can take advantage of nighttime ventilation that can significantly reduce cooling costs. - Find a system that has a check filter light to remind you to inspect the filter after a certain number of operating hours.How do I select the right contractor? System sizing and proper installation are critical to energy efficiency and home comfort. It’s important to hire a qualified contractor who uses Manual J or an equivalent size calculation tool.

If your contractor is certified by North American Technician Excellence (NATE), you know they’ve received special training about how to size and install your system. Note: NATE certification is not required for customers to receive rebates. Resources for finding a contractor: AC Check Trained Contractors North American Technician Excellence (NATE) How are air conditioners typically sized to meet the cooling needs for my home? Your comfort while using air conditioning depends both on reducing air temperature and removing humidity. An air conditioner should ideally run for 20 minutes or more on each cycle to cool the indoor air and to reduce humidity. Oversized air conditioners run in short inefficient cycles. They waste energy since they must run for a few minutes at the beginning of every cycle just to cool down the indoor coil and ducts. Only then can they can cool and de-humidify your home. That original cool-down energy is wasted after the air conditioner shuts off.

What is meant by “BTU” and “Ton?” An air conditioner's ability to remove heat is expressed in BTUs (British Thermal Units) per hour,or "tons" of cooling. Each ton equals 12,000 BTUs per hour, and is equal to the energy contained in a ton of ice, a term left over from the days when buildings were cooled with ice. Your air conditioner should have a ton of cooling capacity for every 400 to 1,000 square feet of floor area, depending on your home's energy efficiency and your local climate. How does insulation affect my cooling needs? A poorly shaded home with little insulation and lots of air leaks might need a ton of air conditioning for every 400 square feet of floor area. A well insulated and well-shaded home with few air leaks might only need one ton per 1000 square feet. Contractors size air conditioning systems using computer programs or extensive hand calculations. To ensure correct sizing, ask your contractor to show you the written calculations for your home.

Then have them install the smallest size air conditioner capable of cooling your home. What is the difference between EER and SEER? EER (energy efficiency ratio) is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level (usually 95° F). A higher EER means the system is more efficient. You can calculate kilowatts if you know the EER and the size, in tons. EER = BTUs of Cooling @ 95F / Watts used @ 95F In the case of a 10 EER, 2 ton air conditioner: 10 EER = 24,000 BTUs Out / 2,400 Watts In For the same size unit, but rated at 12 EER: 2 EER = 24,000 BTUs Out / 2,000 Watts In or 20% more efficient. If you want to calculate kilowatt-hours, just multiply the "Watts In" by the number of hours that the air conditioner is running. SEER (seasonal energy efficiency ratio) is a measure of efficiency over an entire cooling season, as opposed to a single outdoor temperature. Residential units are almost always rated in SEER.

SEER came into use as a more practical measure, since the temperature outside is not always 95º F. Also, the denominator is in watt-hours, not in watts as is the case for EER. The same relationship holds ... a higher SEER means the system is more efficient. SEER is the total amount of cooling the air conditioner will provide over the entire cooling season divided by the total number of watt-hours it will consume or: SEER = Seasonal BTUs of cooling / Seasonal watt- hours used What is the importance of EER? There are many goals and benefits of utility sponsored Efficiency Programs. Among these is education for the purpose of using energy wisely. From this a rating system to establish standards for energy consumption has been developed. One way to measure energy consumption is Seasonal Energy Efficiency Ratio (SEER). SEER is a measure of efficiency over an entire cooling season. SEER ratings are useful in determining the amount of energy used and the amount of energy saved.

Often, the unit of measure associated with SEER is kilowatt-hours (kwh). A kilowatt is 1000 watts used for 1 hour. SEER = Seasonal BTUs of cooling / Seasonal watt- hours used. There is more to energy consumption than kwh. Another measure of energy (and thus energy efficiency) is demand. Demand is the maximum amount of electricity used by an air conditioning system. This usually occurs at start up. The unit of measure associated with demand (or peak) is Energy Efficiency Ratio or EER. EER = BTUs of Cooling @ 95F / Watts used @ 95F. Almost all air conditioning units are tested under the same controlled and specific laboratory conditions to determine the EER rating. Your local sponsors, and the country as a whole, are concerned about using energy efficiently. Efficient usage occurs both in the seasonal and peak arenas. Many advocacy partners in the industry recognize SEER alone does not address demand savings. Use of EER as an industry standard is in an attempt to for continued improvement in demand performance.