Depends on what your electric rates verses the cost of oil are. Electric is about as close to 100% efficient as you can get. Your oil heat could be anywhere from 50-90% efficient (well, the range could be larger). So, hard to say without more info. You can figure out how many BTU/gallon of fuel you get, then compare to electric costs using 1 watt/hour = 3.412142 BTU.