"the allowable tax credit is 30% of the qualified solar system expenditures up to a maximum tax credit limitation of $2,000."
The same site also says:
Solar Energy Systems
Tax credits are available for qualified solar water heating and photovoltaic systems. The credits are available for systems “placed in service” from January 1, 2006 through December 31, 2016. The tax credit is for 30% of the cost of the system, up to $2,000. After December 31, 2008, this $2,000 cap will be removed for photovoltaic systems (but not solar water heaters). This credit is completely separate from the $500 home improvement credit.
Since it is now after Dec 31 and I am considering a PV system, I do not believe the $2000 cap applies.