How old is the house? Sounds like you have a well insulated newer house to have that fuel consumption. My sister is building a brand new house in Boston. The house is crazy insulated and airtight. The heating and cooling loss numbers were insane. Its going to cost practically nothing to heat and cool when I looked over the plans.
Might have been much older mini splits. The stuff coming out in the last year or two are probably twice as efficient. The technology is rapidly advancing and getting more efficientl. I ran some numbers for Taunton MA. It looks like you have municipal power and pay significantly less than the rest of MA so your savings are pretty massive.
At Taunton MA electric rates of .14 a kwh and the mass.gov posted average propane price of 2.92, here is what a million btus of heat would cost you.
Heat pump- $9.33
Propane- $35.52
For others in MA here are the state wide average prices taken from the mass.gov website for comparision.
Heat pump at .22kwh. $14.67
Heating oil $27.45
Propane- $35.52
Natural gas- $26.83
Natural gas is not cheap as cheap as it once was in New England and prices have doubled since the beginning of the year. There is not enough pipeline supply and a huge demand from gas power plants that prices have been high.