I live in Pa. in a 1000 sq ft twin rancher with finished basement. My oil furnace is 45yo - oil costing me $2000+ each year. My rooftop AC unit needs to be replaced; my 1st flr has duct work for AC, not my basement. I intend to stay in the house. I work 2 jobs and will take out a loan so am looking for most efficient and economical answer, for present time and for future. With the current tax and energy rebates available, should I #1: replace AC only and keep oil furnace? #2: replace AC and get new oil furnace? #3: replace AC and convert to gas furnace and pay additional $1100 to get gas line? #4: get a rooftop heat pump and use oil furnace as back up until it goes and then decide to get either a new oil furnace or gas furnace? Need to make a decision quickly as AC prices will rise this month. THANK YOU!!