How Homeowners, Consumers
Can Battle Against Global Warming

Going green is the new black in 2007. Advice abounds on how to cut your carbon dioxide output and do your part in the battle against global warming. But how much does a person have to spend to go green--and what kind of environmental impact would that spending actually have?

The U.S. is the largest emitter of greenhouse gases in the world, accounting for 25% of the world's total. The average American is responsible for about 20 metric tons a year of CO2 equivalent (CO2e), a standard measure of greenhouse gases. That's about 40,000 pounds of CO2e a year, per capita, a far greater number than that of any other industrialized country.

We set out to evaluate a few of the in-vogue recommendations based on what they cost and what they'd do for the environment. In each area we offer up three levels of feasibility--hard, medium and easy. Where possible, we've crunched the numbers to estimate how much a change would cost, how many pounds of CO2e each step can save and the percentage each would knock off one person's emissions.

At Home

Sixteen percent of U.S. greenhouse gas emissions are generated from our homes--from the fossil fuels burned to power our electronics, lighting, heating and cooling systems.

The Hard Way: Buy an Energy-Efficient House

Cost: Energy-efficient homes may cost a few thousand dollars above market value, which would generally add about $10 to $15 to one's monthly mortgage payments. Some will not be valued above market.
Savings: It's estimated that an energy-efficient house will shave $30 off monthly utility bills for an average home, according to Energy Star for Homes, an EPA organization. The average U.S. home is about 2,500 square feet.
Impact: 4,500 pounds of CO2e a year, or 11% of one person's total emissions.

The EPA's Energy Star program works with 3,500 home builders to spur the construction of homes that are 25% to 30% more energy efficient than a home built to the International Energy Conservation Code, which most states use as a standard.

That increase in efficiency comes from increased insulation, better windows, controlled air filtration, and efficient heating and cooling systems. So far, about 750,000 such homes have been built. The EPA expects two million by the end of the decade, reducing the U.S.'s CO2e emissions by one million metric tons.

The Medium Way: Switch to "Green Power"

Cost: $120 to $500 a year. Varies by area and size of home.
Impact: 14,173 pounds of CO2e a year, according to the EPA, or 35% of one person's total. (This number varies depending on the amount of energy your household uses. In New York City, where houses and thus energy bills are much smaller, ConEdison Solutions estimates that its green power purchasers save 4,700 pounds of CO2e a year.)

Go to the Tennessee Valley Authority's Web site, and you'll find a section called Green Power Switch, where customers are encouraged to enroll in a green power program. It seems simple: sign up and the TVA, which services seven states and 8.7 million customers, will bring energy generated from renewable resources, such as solar or wind power, "to your home."

But there's not a switch for each TVA household that can simply be flipped to green. Rather, the TVA takes the extra money that Green Power Switch customers pay and uses it to procure green power, which then gets mixed in to the company's total pool of energy and distributed to the overall customer base.

The TVA tacks on $4 to a customer's monthly bill for each block of green power they buy. (A block is the equivalent of about 12% of a typical household's monthly energy use.) A year's worth of TVA green power -- about 96 blocks -- comes at a premium of about $384 a year on top of your energy bill.

In states with deregulated energy markets, customers can choose to buy green power from an alternative electricity supplier. These costs vary even within a single market; in New York City, for example, Con Edison works with several green power suppliers whose programs cost anywhere from $3 to $20 a month.

The Easy Way: Use Low Energy Light Bulbs

Cost: $19.76 for a 12-pack of GE Energy Smart CFL Light Bulbs, at Walmart.com, or $4.98 for a single Soft White Compact Fluorescent Bulb, at Lowe's and other major retailers. Savings: $30 per bulb
Impact: 1,200 pounds of CO2e a year (for 12 bulbs), or 3% of one person's total.

Only 10% of the energy consumed by a normal light bulb generates light -- the rest just makes the bulb hot. Compact-fluorescent lights convert more energy to usable light and less to heat, requiring 75% less electricity. They're about eight times more expensive at the checkout counter, but will last up to 10 times longer than ordinary bulbs--saving about $30 over the life of each one.

But CFLS aren't no-brainer purchases: Some give off harsher light than others; some work with dimmer switches, some don't. Also be aware that each bulb contains about four milligrams of mercury, a small amount but enough to warrant special disposal. The EPA recommends placing it in a sealed plastic bag and discarding at a local hazardous waste collection site. (Earth911.org can locate the closest site to you.)

On the Road

In the U.S., the transportation sector accounts for about a third of greenhouse gas emissions and is the fastest-growing major source of greenhouse gases, according to a recent EPA draft report. Cars and light-duty trucks contributed to 61% of transportation CO2 emissions in 2005, down from 63% in 1990.

The Hard Way: Get Rid of Your Car

Cost: A year's worth of public transportation varies widely, from $200 to $2,000 depending on location.
Savings: The Sierra Club estimates that the average yearly cost of driving a single-occupant car is between $4,826 and $9,685. Fueleconomy.gov puts the cost of gas alone at about $1,300 for an average car, like a Honda Civic.
Impact: The EPA's calculator estimates that a typical car driven by the average American emits about 12,100 pounds of CO2e a year -- about 30% of one person's total emissions.

Even riding public transport takes its toll, given that buses, subways and commuter rail all emit CO2. Riding a bicycle would save even more emissions and money, but won't be much help when you need to drop the kids at soccer practice.

The Medium Way: Drive a Hybrid Car

Cost: $22,600 (MSRP, Honda Civic Hybrid)
Savings: $445 a year in gas, according to four most efficient models in each vehicle class (sedans, sub-compacts, SUVs, light trucks), fuel economy would be 12% higher and Americans could save 13.1 billion gallons of gasoline -- about 254 billion pounds of CO2e, or 1.6% of the U.S. total yearly CO2e emissions, according to calculations we did based on the EPA's numbers.

For those who own a car that's less efficient than the standard American car, which gets between 30 and 40 mpg, switching to a hybrid can have an even bigger impact. Swapping a Hummer for a Honda Civic Hybrid would save about 13,000 pounds of CO2e a year and $1,676 a year in gas.

The Easy Way: Drive Less and Boost Your Mileage

Savings: Varies. The less you drive, the more you save on gas.
Impact: Reducing the amount you drive by just 2,000 miles can save 1,100 pounds of CO2e a year, or 3% of per capita emissions.

Every gallon of gasoline you save avoids approximately 20 pounds of CO2 emissions, according to the EPA.

Any steps taken to boost a car's gas mileage will also help you reduce emissions. Fueleconomy.gov says that giving a car a tune-up can improve gas mileage by about 4%. Replacing a clogged air filter can get you 10% and simply using the recommended grade of motor oil will up gas mileage by about 2%.

In the Grocery Store

At the end of Al Gore's "An Inconvenient Truth," he rattles off a list of things one can do in daily life to help the planet: switching one's light bulbs and driving a hybrid are both among them. What isn't on that list: your diet.

The Hard Way: Cut Out All Animal Products

Cost: Wouldn't dramatically increase or decrease spending at the grocery store.
Impact: 3,000 pounds of CO2e a year; or 8% of one person's total.

The average American diet produces 3,000 more pounds of CO2e a year than a calorie-equivalent "vegan" diet that is derived only from plants, i.e., fruits, vegetables, beans, according to the authors of a 2006 University of Chicago report.

The savings come from bypassing the livestock industry, which is responsible for 18% of the U.S.'s total greenhouse gas emissions, according to a report by the Food and Agriculture Organization of the U.N. A good deal of that comes from the methane emitted from cow manure (methane is a greenhouse gas), the CO2 produced by the operation of farm machinery and the devotion of colossal amounts of land to grow single crops, like corn. Corn is cultivated with a synthetic fertilizer that emits greenhouse gases in two ways. First, manufacturing the fertilizer--a combination of nitrogen and hydrogen gases--requires large amounts of natural gas. Second, runoff from this fertilizer evaporates into the air as nitrous oxide -- a greenhouse gas hundreds of times more powerful than CO2.

Much of the rest of the food industry's CO2e output simply comes from transporting meat and dairy products around the world, a phenomenon that is not unique to meat -- turning a seemingly clear-cut option into a bit of a puzzle (more on that later).

A vegan diet also omits fish. The University of Chicago report found that the energy involved in the production and transport of certain varieties of fish -- such as tuna and swordfish -- can be just as bad as with meat. If you want to eat fish, one of the report's authors, Gidon Eshel, recommends sticking to herring and sardines, which are found closer to shore and require shorter boat trips to be caught.

The Medium Way: Eat Chicken Instead of Red Meat

Impact: 2,205 pounds of CO2e a year; 6%

According to the Chicago report, taking a smaller step and cutting out red meat -- while continuing to eat chicken -- can save about 2,205 pounds of CO2e a year. Granted, this exact number reflects a somewhat unrealistic dietary change from eating only red meat to only chicken, but Mr. Eshel says it's still fairly accurate.

The Easy Way: Eat Everything, but Make Sure it's Local

Cost: Varies, but can cost more.
Impact: 60-242 pounds of CO2 a year, or about 1%

The diverse bounty of vegetables, fruits and meats found in a grocery store have consumed a lot of energy getting there. The food industry burns nearly a fifth of all the petroleum consumed in the U.S. -- about as much as automobiles do, as reporter Michael Pollan points out in his book "Omnivore's Dilemma." Only a fifth of that energy is used to grow food. The rest is spent processing and transporting it. Eating products that originate close to home can be a powerful alternative to giving up meat, dairy and fish, depending on where you live.

If you're an employee at Google's Mountain View, Calif. headquarters, eating locally won't be a problem. The company's dazzling new employee cafeteria is named Café 150, because it serves only food originating within a 150-mile radius.

For a Fortune 500 company staffed with famous chefs and nestled in a valley lush with farms, ranches and fisheries, eating local isn't so much of a challenge. But sticking solely to local products won't be so easy for individuals living farther a field, so to speak. "It's easy if you're living in the Central Valley," Mr. Eshel says. "But in Vermont, there's no way."

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