Five companies that sell replacement windows agreed to stop making “exaggerated and unsupported” claims about their products’ energy efficiency as part of a settlement announced Wednesday by the Federal Trade Commission.

The companies targeted by the FTC, including Long Fence and Home of Maryland, had all asserted that their windows could help consumers substantially cut energy bills. But federal regulators alleged that the firms could not back up their marketing claims.

The settlement, which remains to be finalized, is part of a broader push by the FTC to protect consumers against deceptive advertising related to products marketed as environmentally friendly now that a growing number of Americans are looking to buy “green.”

Energy-efficient windows have become especially popular in recent years because homeowners who bought them were eligible for a federal tax credit. Window makers and retailers heavily promoted the tax credit, which enabled consumers to claim up to $1,500 in 2009 and 2010 and up to $200 last year, according to the nonprofit Alliance to Save Energy. The tax credit has not been extended to this year.

The government investigated the marketing of energy-efficient windows for about a year before filing a complaint. Companies that signed the agreement include Gorell Enterprises and Winchester Industries, both based in Pennsylvania, and Serious Energy of California and THV Holdings of Kentucky.

None of the companies admitted wrongdoing, and the government is not seeking refunds for consumers. But going forward, the companies must substantiate energy-efficiency or cost-saving claims with reliable scientific data or risk heavy civil penalties, said James Kohm, an associate director for enforcement in the FTC’s Bureau of Consumer Protection.

“We don’t regard [the companies] in these cases as bad companies, and these windows are not necessarily bad windows,” Kohm said. “Our concern was that they overstated the extent to which those windows can save energy or money.”

In its advertisements, Long Fence and Home of Beltsville claimed “50% savings guaranteed” and “Save 50% on Energy Bills — or LONG PAYS YOU!” The company distributes and installs several lines of windows, including Serious Energy’s Quantum 2 windows with SuperPak glass.

In its complaint, the FTC said it is unlikely that Long Fence and Home’s windows would achieve those savings. A home’s location, size, insulation package and existing windows ultimately determine the savings homeowners can realize, the complaint said.

The other companies also had declared that their windows would reduce energy costs by about 50 percent. Serious Energy promised up to $500 to consumers who did not realize its cost-reduction claims on heating and cooling within a year of installation.

John DePaolo, president of Long Fence and Home, said in a statement that the FTC’s efforts will assure “that consumers get the most accurate and up-to-date information” and will better position the industry “to communicate cost-saving benefits to consumers that can be validated.”

The FTC suggests that consumers look for the National Fenestration Rating Council’s label when shopping for windows. The label will rate how much heat escapes from a window and other energy-performance factors.