Purchased New Heater/A/C in 2011--How to Handle Taxwise

1. I have an office in my home. Purchased a new Heater/A/C in September 2011 for ,200 (charged to credit card).

1. In some (but not all) previous years I have claimed a Home Energy Credit for OTHER qualifying items/improvements.

a. Would I still qualify for some/all of the $500 Home Energy Credit for items placed in service in 2011?

b Whether or not I qualify for a 2011 Home Energy Credit in some amount, may I also deduct (or depreciate) some/all of the total cost of the Heater A/C for 2011 and/or for subsequent years?

c.If this is a line item depreciation deduction for 2011,where can I get information about the deductible amount for future tax years? What is useful life of this item and what IRS depreciation table governs things?

I know these questions are basic and answerable somewhere at irs.gov but I do not want to deprive myself of all possible tax benefits (Credits/Deductions/Depreciation) in connection with this rather large improvement to my home and office.

Any guidance or links appreciated.