I own and live in one unit of a double and rent out the other unit. I put in two 95% HE Furnaces in 2010. The total cost of the job was $6,530 which qualified me for the $1,500 federal credit plus $325 (rental unit) and $425 (my unit) in National Fuel rebates. The rental unit part of the job cost $3,410 and my unit cost $3,120. Do I use the full cost of the rental unit furnace for the cost basis for depreciation? If not, the rental furnace was 52% of the total, do I use $3,410 - 52% of the $1,500 credit ($783) - $325 National Fuel rebate for a final cost basis of $2,302? Or do I not have to deduct the rebate?