All of the following equipment generally qualifies for a 30% federal tax credit in the United States. A tax credit is unlike a deduction in that it allows a dollar-for-dollar subtraction from income. The total amount of purchase should be entered into line 53 of the 1040, originating from form 5695. Some rules can be found at http://seia.org/galleries/pdf/SEIATaxManual_v3-0_FAQ.pdf. Some individual states also have rebates, often on sales tax. See the DSIRE web site for more information.