Can I deduct the cost of a new propane/gas generator? Can I deduct the cost of a new propane tank and installation for the generator?

If the generator was installed on your personal residence, not used as a rental or in a business, the cost cannot be deducted on your tax return.  The cost would be added to the basis of the home when it is sold.

No.  Gas home generators are not eligible for the Home Energy Credits.  No, the propane tank is not listed as an eligible product for the energy credits.