I live in the New England - winters about 20F with drops to -10F. The cost of running gas ( $6- 7 per million btu which is comparable to oil) verses continuing with electric ($21+ per million BTU) made converting off electric very cost effective. The payback on the work was about 4 years, and the house was set up for multi zones(forced hot water retrofit). It is important to look at the operating costs of both systems as well as the installation. Electric is generally cheaper to install, but will cost more to run. Have a heat loss calculation done for your house, and find out what the cost for electric and oil will be. There are tables that will let you convert KwH and gallons of oil into BTUs. With that, you can figure out which is going to work better in your situation.