COLUMBIA, S.C. (AP, WLTX) - South Carolina's two largest utility companies have pulled out of a project to build two billion-dollar nuclear reactors.

The reactors were set to be among the first new nuclear reactors built in the U.S. in decades. First, Santee Cooper's board voted on Monday to stop construction. A short time later, SCE&G also said they'd abandon the project as well.

Santee Cooper owns 45 percent of the project, while South Carolina Electric & Gas owns 55 percent. That utility planned to update state regulators on Tuesday.

SCE&G said they made the decision based on the additional costs of the project, as well as other factors. It's estimated about 18 percent of SCE&G customers' bills went to financing the effort.

The project has been shrouded in doubt since earlier this year, when primary contractor Westinghouse filed for bankruptcy protection.

“We arrived at this very difficult but necessary decision following months of evaluating the project from all perspectives to determine the most prudent path forward," said SCE&G Chairman and CEO Kevin Marsh. "Many factors outside our control have changed since inception of this project. Chief among them, the bankruptcy of our primary construction contractor, Westinghouse, eliminated the benefits of the fixed-price contract to our customers, investors, and other stakeholders."

The utilities announced last week that Westinghouse's parent company, Toshiba Corp., agreed to jointly pay them $2.2 billion regardless of whether the reactors are ever completed.

The reactors were planned for the V.C. Summer Nuclear Station north of Columbia in the town of Jenkinsville. SCE&G says they'll likely have to pursue natural gas as a way to generate the power that the nuclear plant was to have created.

The South Carolina Electric Cooperative, which is Santee Cooper's largest customer, says it backs the decision as well.

“It’s the right decision at the right time,” said Michael N. Couick, president and CEO of the state association of electric cooperatives. “But it was also the right decision to start construction of the nuclear generators in the 2007-2008 time period, contrary to many critics with convenient 20/20 hindsight.”