You would want to do is have a full evaluation of your home energy efficiency. Call PSNH and they will evaluate you home for free. Not sure if NH-CoOp will do the same.
Lots of factors will determine which is efficient. Gas, electric or oil, steam, forced hot water, hot air, or baseboard heating. Any environmental engineer or 'Green' architect can give you great advice.
I have condo built in 1978. a duplex, all on one floor. Last summer, I was told by an environmental engineer to replace the forced hot water oil burner with a tank to a tankless Rinnai gas hot water unit. It was surprisingly small and it is on demand. Gas because I have natural gas pipeline available. It is so efficient, the exhaust pipe is PVC, not metal. This is great as the condo is is only a weekend home. I was burning oil while I was away. Gas was only needed to maintain a 50 degrees temperature. The Rinnai heats up the unit a lot quicker. Long showers are not a problem. Before, one must wait a half hour before another take a shower.
I have determined my gas bill is about half of what my oil bill was. Oil may be cheaper but the efficiency makes a difference.
