Ten years ago the honest answer to this question was "keep the oil boiler." Heat pumps lost most of their output below 20 degrees, and a Somerville or Winchester home needed a backup system to get through February. That is no longer true. Cold-climate heat pumps from the major manufacturers deliver full rated heating well below zero, and the ones we install across Greater Boston carry the house through January without an oil burner in the basement.
The economics have changed too. Oil prices swing hard, an oil boiler needs a paid annual cleaning, and the tank itself is a liability as it ages. A heat pump runs on electricity, gives you central or ductless air conditioning in the same equipment, and Mass Save currently offers substantial rebates for whole-home heat pump installations that replace oil or propane. Those incentives are the single biggest reason the conversion has become so common around Boston.
That said, a heat pump is not automatically the right call. If your oil boiler is under ten years old, well maintained, and feeds a steam or radiator system you like, a repair or tune-up is cheaper and keeps a system that works. If the house has no ductwork, a conversion means a ductless system with indoor heads in each zone, which is excellent in a triple-decker or a cape but needs some planning around placement.
The right way to decide is with a heat-loss calculation, a look at your electrical panel, and a written comparison: cost to keep the boiler running for five more years versus the net cost of a heat pump after rebates. Garcia Services HVAC does that comparison at no charge, and we service oil boilers and install heat pumps, so we have no reason to push you either direction.