Air conditioning is a growing source of domestic energy use: 87% or American homes installed room or central A/C as of 2009. In the U.S., air conditioning costs homeowners $11 billion per year and accounts for roughly six percent of home energy use. Six percent may sound low, but it’s misleading: Most energy sources, such as lighting, water cooling, and refrigeration, are spread roughly evenly throughout the day and the year. Even space heating, which accounts for 42% of home energy use, is spread throughout the cold-weather months, and often is on a separate heating oil or gas bill. Air conditioning, however, has highly concentrated use on the very hottest days of the year, particularly during the hottest afternoon hours.
Consequently, homeowners and businesses can see their electricity bills spike in the summer after a stretch of blisteringly hot weather. Cooling costs can account for half or more of your power bill – which means a doubling in summer months (or more). These spikes in power bills can be particularly intense if ratepayers have variable-rate plans – i.e. plans that have an electricity price that changes throughout the day. When demand is high – which is also when everyone is using their A/C – prices can get very high.
Cutting back on air conditioning is also good for the environment because it reduces carbon emissions. While saving electricity is always virtuous, in the dog days of summer it’s especially true: Many utilities run their dirtiest coal plants only when demand is at peak – precisely when you (and all your neighbors) are running your A/C on full blast.
There are many straightforward approaches to taming your electricity bill in the summer by cutting back on air conditioning. Here are our top ten tips.
- Give your air conditioner a checkup – or a replacement. This one is perhaps the easiest one on the list, and most important. Clearing a clogged A/C unit filter alone can save 5 to 15 percent in energy use – and will help it work better and not break down. If your air conditioner is more than ten years old, it may be time for a new one, which could save lots of energy in a jiffy if it’s much better than what you currently have, you live in a hot climate, or both.
- Adjust your thermostat. Many people don’t think to adjust their thermostat in hot weather. And yet, just a couple degrees can make a huge difference: One study found that each degree a thermostat is set above 75⁰F could save 10% to 15% in energy. Many experts recommend setting the temperature at 78⁰F on hot days, and 82⁰F – 85⁰F when you’re outside the house. Get a programmable thermostat so you don’t have to remember to set it when you leave.
- Use fans instead of A/C. Ceiling fans may be low-tech, but they work wonders. A ceiling fan can cut back on air conditioning needs, saving up to 40% on electricity. Portable fans are great too, and can be positioned strategically. Fans also don’t actually cool the air; they just make it feel cooler by moving it, pulling body heat away from your skin. Fans use roughly 1/60th the energy of an air conditioner, so even using both at the same time is efficient if you raise the thermostat. Make sure your ceiling fan has angled blades and that the air is pushed downward at you. Lots of helpful tips on fans can be found here.
- Open your windows, especially at night. There is a very simple cooling technique – cross ventilation. Like fans, opening two or more windows in a room or house will help circulate air, and at night can bring in the cooler outside air to replace the overheated indoor air. This is particularly helpful in drier or more northern regions that cool off at night.
- Turn off the A/C when you’re not using it. Don’t waste air conditioning you don’t need in rooms you’re not using or when you’re outside the house. Sound simple? Many people forget, going to work or school or skipping town without turning off the A/C. Again, a programmable thermostat, many retailing at less than $100, will help with this.
- Bulk up on shade, part I: blinds. Your air conditioning works the hardest in sunny rooms that heat up like a greenhouse. Simple solution: install venetian blinds, light-colored curtains, or any other device to keep sunlight from entering your home.
- Bulk up on shade, part II: plants. Planting shrubs and trees, particularly on the south and west sides of your house in front of windows, can not only block the sunlight from entering the house, but can absorb the heat and help provide cool from their transpiration, or water loss from leaves. They also absorb much less sunlight and heat than other built surfaces (including your walls and roof), which radiate that heat day and night after a hot sunny day (like a hot sidewalk on a summer night). Having an outdoor A/C unit shaded, usually by plants, can raise its efficiency up to 10%.
- Cook outside – or not at all. It’s hot in the kitchen – because the stove and oven are hot. Even appliances like refrigerators and electronics create heat, but the stove is the biggest culprit. Cook outside on the grill or eat chilled dishes to avoid making your A/C work hard in the dining area. The microwave is also a better option than the stove top.
- Keep your roof a light color. Think your roof color doesn’t matter? Think again. Just like a black shirt or black car will get hot, a dark roof will bake the rooms right under it. Dark roofs can reach temperatures of 150°F or more in the summer sun. A cool roof, painted a light color or made of reflective material, under the same conditions could stay more than 50°F cooler.
- Retrofit your home by keeping out the hot air. If you live in a particularly hot climate, keeping out the hot air in summer may be as important for climate control as keeping out the cold in the winter. The most cost-effective construction-related cooling strategies for sealing in the air include quality insulation, tight duct work, quality air barriers, and shading or glazing windows. Solar screens on windows can capture 70% of the sun’s energy before it enters your home.