While staying with a college friend last weekend, I woke to the noise of a workman who was installing a new geothermal system for the house.

Her husband had warned me there may be an early-morning racket, but honestly, it was a welcome wakeup. I am no fan of air conditioning, but blistering heat has been blanketing much of the eastern United States. It’s the kind of heat that kills people who can't get relief, and ACs have become essential equipment in most American homes -- 87 percent of households now have them, up 20 percent since 1993.

This climate control, however, comes at a cost. The average household spends more than $2,200 a year on energy bills, with nearly half of this going to heating and cooling. Saving money was one of the main reasons my friends went geothermal. Now that its installation is complete, they say the system should cut their household heating and cooling costs by 70 percent.

What struck me first was how quiet the system was compared to the average window-box AC, and the cool felt more natural and comfortable to the skin. But what truly sets geothermal apart is how much more energy efficient it is than electricity. These systems can move as much as three to five times the energy as it heats or cools a home, which is why users can save hundreds of dollars in power costs each year. And because geothermal systems are transferring heat, not generating it by burning something, they don't emit carbon dioxide, carbon monoxide, or other greenhouse gasses. In contrast, the average air-conditioned home emits roughly 2 tons of carbon dioxide annually. *

Still a mere fraction of the energy market, more than 600,000 geothermal systems supply climate control in U.S. homes and other buildings. New installations are occurring at a rate of about 60,000 per year, and recent policy developments are offering strong incentives for homeowners to install more. For instance, the 2008 economic stimulus bill, Emergency Economic Stabilization Act of 2008, includes an eight-year extension (through 2016) of a 30-percent-investment tax credit (with no upper limit) to all home installations of EnergyStar certified geothermal heat pumps.

While the tax credit may cut upfront costs in half, installing geothermal in your yard takes time and planning (and depending on where you live, may not even be possible). But once planned, installation should take no more than a couple of weeks. That said, in this current heat wave, you likely want to cool down right now. You can learn more about geothermal systems here, but in the meantime, follow these low-cost cooling ideas to get you through the hottest days ahead:

• Shade the house: Awnings, shutters, and overhangs provide a good defense against the summer sun. Trees and tall bushes also beautify your view while reducing the amount of sunlight that enters your windows.
• Close the blinds: Shutting curtains, shades, or blinds on the sunny side of the house can make a big difference. Blinder venetian shades with highly-reflective light colors, in particular, can reduce heat build-up in your home.
• Create a breezeway: When it’s not too hot out, pull in cool air by cracking open lower-story windows just one or two inches and face portable and window-mounted fans inward. For upstairs windows, face the fans outward to remove air that risen due to convection in your home. This will create a stronger draft throughout the house that will keep the air cooler without the use of AC. If the outside temperature is more than 77 °F, it's better to shut all the windows and pull the shades.
• Tell your AC what to do: A programmable thermostat lets you save money by turning the AC off when you're not around to enjoy it. Set the temperature at 80°F when you know you'll be away, and when your home, try setting it at least 2 degrees higher than you would normally do. A shift from 72°F to 74°F in the summer will leave the room feeling just as comfortable, but it could mean real savings on your annual energy bill.
• Upgrade your AC: Whether it's central air or a window-mounted AC, if your cooling system is several years old, you will most likely save money by upgrading to new, more efficient models. The most efficient models use inverter technology (which also makes them very quiet), and 30-percent tax credits are available for units 16 SEER and better. Depending on the age of your current unit, Energy Star-rated air conditioning could save you 10 to 30 percent of your cooling costs. Remember to clean or check the AC filter once a month as any build-up will restrict airflow and make it less efficient.
• Install ceiling fans: Fans use 10 percent of the energy consumed by AC but can make a room feel 10 degrees cooler, and replacing your AC with a ceiling fan could save you a couple hundred dollars or more a year.
• Give your appliances a break: Remember it's summer. Dry your clothes on a clothesline, grill outside, and dine by candlelight. You could also turn off your computers and entertainment equipment at night.

Finally, remember to take care of yourself on hot days, too. Drink lots of water. As you perspire, you lose water to dehydration and your body temperature rises. So replacing fluids is essential to keeping cool. Doctors recommend drinking at least two liters of water a day, with a third liter on hotter days. Eat lots of fruits and vegetables, as they are filled with water and avoid sugary drinks that dehydrate you (soda, coffee, alcohol, etc.).

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Image: db0yd13