I'm not sure that I would switch from oil to propane. I would switch to natural gas in a heartbeat, but that's tough to do if there are no lines in the area. My understanding is that propane is made from oil and is a byproduct of natural gas production with the US supply almost equally split between the two. I would do a close analysis including payback period for equipment investment. I'm thinking that when we get an administration that is more friendly toward oil production, prices will come down, although that is at least 4 years away. In the mean time it looks like it is still too close to be worth it. If I use the official numbers, it isn't worth it.
http://www.nh.gov/oep/programs/energy/fuelprices.htm