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?

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 United States is the largest emitter of greenhouse gases in the world, accounting for 25 percent 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. 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.

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. We offer 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.

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 percent of one person's total emissions.

The EPA's Energy Star program works with 3,500 home builders — including 225 in Oregon — to spur the construction of homes that are 25 percent to 30 percent 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 2 million by the end of the decade, reducing the United State's CO2e emissions by 1 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 percent of one person's total.

Go to the Pacific Power's Web site, and you'll find a section called Blue Sky, where customers are encouraged to enroll in a green power program. Pacific Power offers three renewable-power options to its Oregon customers, and the company says more than 20,000 Oregonians are purchasing electricity generated from wind, biomass and solar.

One option, called Blue Sky Block, lets you purchase wind energy in 100 kilowatt-hour (kwh) increments called blocks for an additional fixed cost of $1.95 per block per month. You can buy as many blocks as you'd like, allowing you to match a portion or all your energy usage to new wind resources around the region.

A second option, called Blue Sky Usage, equals your total monthly usage and features energy from 100 percent new renewable sources — wind, biomass and solar. For the average home using 1,000 kwh monthly, Blue Sky usage would cost about $8 more per month. You would prevent almost 24,000 pounds of CO2 emissions annually — as much as your car makes when driven about 25,000 miles.

Blue Sky Habitat works like the Usage option, but also includes a $2.50 monthly donation to The Nature Conservancy, a nonprofit organization dedicated to the restoration of native salmon habitat. The average additional monthly cost for this option is $10.30.

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 percent of one person's total.

Only 10 percent 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 percent 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 4 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 percent of transportation CO2 emissions in 2005, down from 63 percent in 1990.