South Carolina residents who are shopping for a new, energy-efficient appliance may want to wait until Friday, when a brief window will open for a new round of rebates offered by the S.C. Energy Office.

Those who just bought such an appliance are out of luck, because the rebates aren't retroactive.

What's happened is that the Palmetto State had a little federal stimulus money left over from 2010, when it received $3.9 million to use for appliance rebates.

At that time, rebates of up to $500 were available for a wide range of appliances, including heat pumps and tankless water heaters.

Most of the money was claimed in just two months.

Later, some of those claimed rebates were canceled, because purchases were returned and for other reasons, said Rebecca Griggs of the Energy Office. So the state ended up with about $325,000 to either use for more rebates or return to Washington.

"We wanted to be able to extend this program again, because it was such a success on the first go-around," Griggs said.

This time smaller rebates are available, for just four types of appliances, and the items must be purchased no sooner than Friday and no later than Feb. 5 to qualify for the money.

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People who buy a clothes washer, dishwasher, refrigerator, or window unit air conditioner bearing the "Energy Star" label during that brief period could get a $100 rebate for a clothes washer, and $50 each for the other appliances.

The appliances that are being replaced must be disposed of.

The idea behind the rebates is to reduce energy and water consumption through increased efficiency, while also encouraging consumers to stimulate the economy by buying new appliances.

In order to get a check, a rebate form available on the South Carolina Energy Office's website must be mailed within five days of the qualifying purchase, along with details of the purchase and a receipt.

"We feel like we'll be able to cover the rebates for that time period (with the available federal funding)," Griggs said. If not, the Energy Office has some funds it can tap to address any shortfall.