Editor’s Note: This piece is part of an ongoing series called “Get It for Less” that will appear every week on MainStreet, so check back for more shopping tips on your favorite products. NEW YORK (MainStreet) – It was an unseasonably warm winter in much of the country, and here in New York it’s already hitting the 70s. That means it’s time to start thinking about putting an air conditioner or central air system in your home. Buy during the winter.If you’re in the market for a new air conditioner, the best time to buy it is during the cold months, when no one else is thinking about air conditioning and prices are low. So if you were in need of a new unit for this summer, hopefully you acted during the fall or winter when units and installations alike were on sale. “You need to replace these things before it’s boiling,” she says. “A lot of stores will offer a discount in the offseason, and if you can catch a [HVAC] contractor in the fall or spring when they’re not busy you can negotiate with them.”

Much like an iPhone, when you buy an air conditioner you’re not just paying the sticker price – you’re also setting yourself up for monthly service charges. In this case, those charges come in the form of higher electric bills, so you’ll want to aim for a fairly energy-efficient unit. In our guide to air-conditioner shopping, we note that getting an Energy Star-qualified unit should mean 10% lower energy costs, which will come out to $60 less during the course of the unit’s life. But there are other ways to make things efficient, specifically by keeping your house cool in other ways to make the air conditioner’s life easier. Huffstetler has previously written about several such tips, including keeping plants in front of the south-facing windows to keep out sunlight (as well as planting for shade around an exterior condenser unit so your central air system has to work less hard to cool the outside air). She also encourages people to consider how appliances in your house can raise the temperature, and suggests turning off your computer when not using it, switching to cooler compact fluorescent lamp light bulbs and avoiding using the dryer whenever possible. 

Get some financial help.If you’re spending thousands to upgrade your central air system, you don’t have to shoulder the full cost by yourself. Huffstetler says that when she recently upgraded her own system, she had a representative from her utility company perform an energy audit to confirm that she needed a new system, which netted her a $250 incentive. She likewise got a state incentive in the form of a Visa prepaid card, as well as a federal tax credit for installing a more efficient system. You’re not the only one who wants to be more energy-efficient – the government also has an interest in promoting efficiency, so see what sort of incentives it’s offering to upgrade your system. Matt Brownell is a staff reporter for MainStreet. , or follow him on Twitter @Brownellorama. Network with Industry Professionals Science and Technology for the Built Environment Supplier Directory & Sponsored White Papers Citation and Abstract Services Publication Updates and Errata

Standards, Research & Technology Standards Forms & Procedures Purchase Standards & Guidelines Resilience Activities in ASHRAE Advanced Energy Design Guides HVAC Design and Operation Training 2017 Las Vegas Winter Conference Courseswindow ac unit operating cost ASHRAE Courses at Industry Eventsdo ac units need water Self-Directed or Group Learningcheap outside ac unit Rules of the Board ASHRAE Associate Society Alliance Young Engineers in ASHRAEResources & Publications | Choosing the Right System for Your Home Buyers Beware: Correctly Sized Air Conditioners Save Money! When you buy a new air conditioning or heating unit to replace your old one -- or if a completely new system is being installed in your new home -- the installer needs to know how big or, more importantly, how small the unit should be.

In order to know exactly how big (or small) it should be, the contractor needs to calculate how much cooling and heating capacity it must have to keep the occupants comfortable. This is called the load of the home. The load of the home is partly dependant upon the home’s square footage. However, a true load calculation goes beyond that. An accurate load determination includes building construction; orientation to the sun; “R” value of the insulation; number, size, and placement of rooms; number, size, and placement of windows and doors; types of windows and doors (thermal efficiency); number and arrangement of floors; Residential load calculations make use of mathematical formulas that take all these variables into consideration. They have been computerized, so they’re not as time-consuming as they were in the past. Determining the load by using rules of thumb almost always leads to an over-sized heating and cooling system, resulting in an increased initial cost, increased monthly utility bills, increased maintenance, and shortened equipment life because the equipment cycles off and on too frequently.

Who Does the Load Calculation? The contractor you choose to install your new system should be able to perform these calculations. You may ask him for this service. If he doesn’t want to do it, or says it isn’t necessary, you may want to look for a different contractor. In some areas, the local utility will perform a load calculation – check with your local utility. How Big Is Big? Cooling size is given in tons of cooling; 1 ton = 12,000 Btu/h. 'SEER' (Seasonal Energy Efficiency Ratio) indicates the efficiency of the air conditioning unit, not its capacity. Why it’s Important to Have the Right Sized System Having the wrong-size heating-cooling system can lead to multiple problems. Over-sizing your cooling system is not a good thing. Without getting into too much detail, your cooling load consists of two parts: We’ve all heard the saying, “It’s not the heat; A cooling system that is too big cools down the temperature very quickly, but it does not run long enough to remove sufficient moisture or “humidity” from the air.

The result is you feel cool but clammy. Many people then turn down the thermostat to make the air conditioner run longer, increasing the utility bill. In some cases, the insufficient moisture removal resulting from over-sized cooling equipment can lead to mold growth and other types of moisture-related damage. A correctly sized cooling system runs long enough to “wring” moisture out of the air. This allows you to be comfortable at a slightly higher thermostat setting and allows you to save money on your utility bill. It also takes care of the “mugginess” without making you feel too cold. Air conditioning systems are sized in “tons,” which is a measure of the rate at which they deliver cooling, not how much they weigh. One ton of cooling is equal to 12,000 Btu/h (British Thermal Units per hour), the rate of cooling required to freeze one ton of ice at 32°F in one day. It is better to have a system that supplies a little less than the required tonnage of cooling, rather than a system that supplies more than the required tonnage of cooling.