Also, you can use their advanced search, choosing "Must contain the phrase in the body": tax incentives and "must contain the words in the body":residential pennsylvania, to get 22 hits on PA, for example. You can also try searching in usa.gov, which has a very "Google like" search engine. The search: "solar energy tax credits" gets 45 hits; "solar energy" "tax credits" "new york" gets 100 hits.
In each state (use www.state.[2 letter state code].us), try browsing for their energy or environment departments. [state].gov also works, as in maryland.gov, ohio.gov, etc. For example, ohio.gov has an index link at left to "Government:, then to "State agencies and departments", then "Energy Efficiency", which has a "Grants and loans" link in its index column on left. In addition, the state pages often link to local governments - which may have local incentives.
Please let me know at email@example.com , or leave a new comment here at Radical Reference, if we need to look for more (or different) information on this.
University of Maryland
Engineering & Physical Sciences Library