Although there are several energy credits available for purchases made in 2007 none of them are related to appliances.
The tax credit is to improve the energy efficiency of existing homes. The law provides a 10 percent credit for buying qualified energy efficiency improvements. The following items are eligible:
In addition, the law provides a credit for costs relating to residential energy property expenses. The following items are eligible:
For more information see http://www.irs.gov/newsroom/article/0,,id=154657,00.html
I hope the information is helpful even though it may not allow you a credit for 2007.