When high school science teacher Ray Janke bought a home in Chicopee, Mass., he decided to see how much he could save on his electric bill.

He exchanged incandescent bulbs for compact fluorescents, put switches and surge protectors on his electronic equipment to reduce the "phantom load" – the trickle consumption even when electronic equipment is off – and bought energy-efficient appliances.

Two things happened: He saw a two-thirds reduction in his electric bill, and he found himself under audit by Mass Electric. The company thought he'd tampered with his meter. "They couldn't believe I was using so little," he says.

Mr. Janke had hit on what experts say is perhaps the easiest and most cost-effective place to reduce one's energy consumption: home.

Moving closer to public transportation or riding a bike instead of driving is not an option for many, but changing incandescent bulbs for fluorescent and buying more efficient appliances is not only possible, it quickly pays for itself with savings.

In the end, not-very-glamorous changes like these as well as obsessively sealing and insulating your home will save more than, in the words of one expert, "greenie weenie" additions like green roofs and solar panels. Twenty-two percent of all energy in the United States is used for residential purposes. (Transportation accounts for 28 percent.) And although residences consume only about two-fifths of this as electricity, because electrical generation is inherently inefficient, it accounts for 71 percent of household emissions. A home's electrical use may be responsible for more CO2 emissions than the two cars in the driveway. Ultimately, changes made at home may be the quickest, cheapest, and easiest way to reduce one's carbon footprint.

The future apparently holds less-snowy winters, earlier springs, and hotter summers because of human-produced greenhouse gases, scientists say. Accumulating evidence supports climate scientists' gloomy forecasts. Five of the hottest years measured since modern record keeping began a century ago occurred in the past decade, according to the National Aeronautics and Space Administration. Last year, the year of Katrina and Rita, set records for hurricane activity.

"If you love your children, replace your lights," says Joseph Lstiburek, principal engineer of Building Science, a Boston-based consulting company that specializes in building technology.

The No. 1 contributor of carbon emissions worldwide is the US. It is responsible for 22 percent of the world's annual emissions. In second place, China produces 17 percent, while Russia at No. 3, contributes 6 percent. By another measure, of the top five producers (responsible for more than half of global emissions), the US is by far the highest per capita contributor – 20 metric tons per person per year compared with China's 3.6 metric tons. (Unless otherwise noted, all statistics are from the US Department of Energy's Energy Information Administration.)

But the flip side of these numbers is that, of the top five CO2-producing countries – India and Japan are fourth and fifth, respectively – an individual American can have the greatest impact in reducing carbon emissions.

The best place to start is to reduce electricity consumption. Power plants lose two-thirds of their energy in waste heat. For every one unit of electricity your space heater consumes, for example, two units have been lost at the power plant. This inefficiency is reflected in electricity's cost to consumers. Even though more American homes use more natural gas than anything else, homeowners spend more than twice as much on electricity – $100 billion annually compared with $47 billion. Not only is electricity more expensive, but because of its inherent inefficiency, it contributes 21 percent more CO2 annually than does transportation.

Cutting back on electricity used for lighting (9 percent of residential usage nationwide) presents the quickest savings-to-effort ratio. The EPA estimates that changing only 25 percent of your home's bulbs can cut a lighting bill in half. Incandescent bulbs waste 90 percent of their energy as heat, and compact fluorescents, which can be up to five times more efficient, last years longer as well.

Second stop, kitchen appliances, which consume 27 percent of the average US household's electricity. More than half of that goes to your refrigerator. So "any fridge over 10 years old is worth changing," says Henry Gifford, a New York-based mechanical system designer. "And no, don't put it in the basement and plug it in and leave it there." Get rid of it.

For the reasons mentioned above, using electricity for water and space heating, which accounts for 19 percent of home electrical use nationwide, should be avoided. "One of the worst things you can do with electricity is use it to make heat," says Alexander MacFarlane, director of green building technical services at the New York-based Community Environmental Center, a consulting company in energy efficiency.

Ideally, all appliances should be exchanged for those bearing the EPA's Energy Star seal. Plugging electronics into power strips, which can then be turned off, will decrease "phantom loads" and further increase savings. (Transformers inside electrical equipment convert your wall socket's alternating current to the direct current electrical devices use to function. Even in "off" position, they often continue to draw small amounts of electricity.)

The reduction of heating costs, where US residences consume 47 percent of their overall energy, is more complicated and begins with an exercise in visualization. A house should be conceived of as an airtight, insulated box where you manage airflow, humidity, and heat. "Build tight and ventilate right," says Mr. MacFarlane.

Individual thermostats in rooms keep energy from being wasted where it's already warm – on the south side of a house, say. And not only external walls should be sealed and insulated, but also between floors to prevent the "stack effect." Hot air rises through badly sealed buildings the same way it goes up a chimney. The upper floors overheat, leading people there to open windows for relief, Meanwhile, a cold draft is sucked into the lower floors. So people living there then crank the thermostat higher, exacerbating the problem, says Chris Benedict, a New York-based architect who specializes in energy-efficient building.

The extra money spent on caulking, using high quality insulators like blown-in cellulose, and windows with high thermal resistance translate into far less energy spent to control indoor temperatures, she says.

The lower price of the smaller boilers and air-conditioning units needed for well-sealed and insulated buildings also balance this higher cost. Ms. Benedict brings her new buildings' energy needs down to 15 percent of the area mean – and this for the same cost as regular construction. (With gut renovations, she reduces it to 50 percent.)

And now – only now – should you consider solar panels. "Go for the efficiency, then go for the solar," says MacFarlane. "Solar panels are the badge that the building gets to wear when you do everything else right."

• The US government has a home energy saver calculator at: hes.lbl.gov. The Energy Star program website: www.energystar.gov. For tips on sealing your home, go to: www.energyconservatory.com.