More people fight over the thermostat than the remote and those battles become more pitched during periods of extreme heat. The disputes aren’t just about comfort, they’re about money too because every time you lower the thermostat in hot weather it raises your electric bill. So what’s the best setting for your central air conditioner? Well, that depends on whether you care more about keeping cool or keeping your utility bill in check. Fortunately, there’s a happy medium. Energy Star says, for optimal cooling and energy efficiency, the coolest you should keep your house is 78° F and that’s only when you’re at home and awake. A programmable thermostat makes it easy to match your cooling needs to your schedule but you can make the adjustments manually if you don’t have one. Try the following setpoints: • 78° F when you’re home. • 85° F when you’re at work or away. • 82° F when you’re sleeping. More heat tolerant folks can experiment with the temperature, raising it one degree at a time to see how it affects your comfort and your budget.

You’ll save 3 percent on your air conditioning costs for every degree you raise the temperature. If you aren’t comfortable at 78° F, lower the temperature a degree at a time. A ceiling or box fan causes a wind chill effect that enhances cooling, helping you feel comfortable at a higher temperature as long as the humidity isn’t too high. Of course, if you live in an area with more moderate temperatures, you may not need your central air conditioning all day and night. If so, you can take advantage of cooler night temperatures by keeping your windows open overnight. Close them on hot days and keep your shades and curtains drawn when it’s sunny outside. If you need the AC when you get home, you can program it to go on before you arrive or turn it on with a smartphone app.It’s more difficult to reach the perfect temperature when you have a window air conditioner. Because the thermostat is in the unit itself, it registers the temperature in that part of the room and may not provide a consistent temperature throughout the space you want to cool, depending how big and open it is.

That means getting the right comfort level is more trial and error. Start with it set at 78 degrees and see how you feel. If you have a window unit in your bedroom, turn it on 30 minutes or so before you go to bed so you’re not cooling an empty room.wall unit air conditioner discount Ways to beat the heat. ac power supply testingNo matter what type of air conditioning you have, it’s easier to keep the temperature at a comfortable level if you can prevent heat from getting into your home. cleaner for ac unitThe three main sources of unwanted heat are heat that seeps in from the outdoors, waste heat given off by appliances and incandescent lightbulbs, and heat from sunlight shining through the windows. During a heat wave, avoid using your washer, dryer, and dishwasher during the heat of the day and make sure you use the exhaust fans in your kitchen and bathroom when you’re cooking or taking a shower.

Cook outside on your grill.Consumer Reports tests energy-saving programmable thermostats with and without remote access. Our top-rated thermostat with remote access is the Honeywell RTH9590WF, $300, followed by models from American Standard and Trane. The best thermostat we tested without remote access is the Honeywell Prestige HD YTHX9321R, $250, followed by models from Lux and Robert Shaw. How do you keep your cool? Let us know below.Dear EarthTalk: Now that hot weather is coming, I want to upgrade my home’s A-C. Which are the most energy-saving models and should I go central air or window units?—Jackie Smith, Cary, N.C. According to the American Council for an Energy Efficient Economy (ACEEE), energy consumption for home air conditioning units accounts for more than eight percent of all the electricity produced in the U.S., at a cost to homeowners of $15 billion annually. Besides the cost, all this cooling leads to annual emissions of about 195 million tons of CO2—or two tons per year for each American home with A/C.

Of course, foregoing A/C entirely is the most energy- and cost-efficient way to go, but some of us need a little cooling for comfort, especially in warmer climates. If A/C is a must, buying the most efficient model is the way to save money and pollute less. Fortunately, a new generation of much more efficient room and central A/C units means that upgrading will likely pay for itself in energy savings within just a few years. The main factors to consider in choosing a new model are cooling capacity (measured in British Thermal Units, or BTUs) and Energy-Efficiency Ratio, or EER. To determine the correct BTU rating for a given space, multiply the square footage by 10 and then add 4,000. Meanwhile, a given unit’s EER is the ratio of cooling output divided by power consumption—the higher the EER, the more efficient the air conditioner. According to the U.S. Department of Energy, national appliance standards require room air conditioners to have an EER of 8.0 to 9.8 or more, depending on type and capacity.

Units with an EER rating of 10 or above typically qualify for the federal government’s ENERGY STAR label, which appears on especially energy-efficient appliances. Check out the ENERGY STAR website for lists of qualifying A/C models. The Association of Home Appliance Manufacturers (AHAM) says that the average EER of room A/C units rose 47 percent from 1972 to 1991. To wit, replacing an older room unit with an EER of five with a new model with an EER of 10) would result in a 50 percent energy cost savings associated with A/C. As to whether room units or central A/C makes more sense, it depends. Room units, which only cost a few hundred dollars each, will suffice for renters or those who only need to keep one or two rooms cool at a time. Meanwhile, central A/C is more efficient overall at keeping a whole house cool, and will also do a better job at reducing household humidity than even several individual room units—and will save more money faster on electricity bills. But with a starting price of around $4,000 for the condenser and initial set-up (plus any duct work needed to distribute cool air around a home), central A/C isn’t for everyone.