Breaking News: President Obama signs stimulus plan into law, includes up to $1500 tax credit only for windows with .30 u-value or lower. All windows Cardinal Builders offer meet or exceed requirements to earn tax credit. Click here for more information.

So read the red banner at the top of the home page of Cardinal Builders' Web site. The Columbus, Ohio, home improvement company wasted little time making homeowners aware of the energy tax credits included in the American Recovery and Reinvestment Act, passed last month by Congress and swiftly signed into law.

They were far from alone. All over the Web, companies selling replacement windows ? intent on capturing the lion's share of the energy tax credit bucks ? leaped into action. Windowizards, of Levittown, Pa., started to run print ads that show Uncle Sam offering a fistful of cash. "Good Thing You Waited," the ad says.

A&A Services, of Salem, Mass., which bills itself as Boston's Best in Home Improvement, featured a March 1 blog post on its Web site explaining the tax credits and, especially, how windows would qualify to earn homeowners that credit.

American Exteriors, of Littleton, Colo., was promoting tax credits at the local home show. "Not a lot of homeowners know much about it," says Greg Garcia, vice president of marketing. Neither, it seems, do all that many home improvement companies. "There's a lot of confusion out there right now," A&A Services owner Chris Zorzy says. "A lot of [home improvement companies] think they can give this thing out, and they don't qualify."

30/30

Window replacement companies can't be faulted for an excess of enthusiasm. U.S. window sales peaked in 2005 and have been falling ever since. Last year window replacement companies across the U.S. watched sales slow and lead costs climb as the recession deepened. For many, the $1,500 available to homeowners from the federal government in 2009 and 2010 in the form of tax credits is the first piece of good news in a long time. Properly promoted, it could tap the repository of pent-up demand that many feel now exists and get the phone to ring. Properly explained, it could move fence-sitters to sign on the dotted line.

But the good news carries a caveat: The government not only upped the amount of money that homeowners can take as a tax credit ? from $500 to $1,500 on a one-time basis, with no $200 subcap for windows, as previously ? it also raised the standards that qualify windows for that credit.

To qualify for the $200 tax credits available in 2006 and 2007, windows had to be Energy Star-rated and bear the Energy Star label. Under the new legislation, windows must have a .30 or less U-factor and a .30 or less Solar Heat Gain Coefficient.

U-factor is a measure of the heat flow through the window. The lower the U-factor, the more efficient the unit. Solar Heat Gain Coefficient (SHGC) is the percentage of heat gained from both direct sunlight and absorbed heat. The smaller the SHGC, the greater the window's ability to reduce the solar heat gain of the home.

Unless the windows that homeowners buy meet the "30/30" criteria, they aren't eligible for tax credits. To get those credits, come tax time consumers must submit IRS form 5695, along with a receipt for the window purchase and manufacturer labels for every window.