The household
A condo unit in a Boston triple-decker, roughly 1,500 square feet, currently heated by an 85% AFUE oil furnace with window or through-wall AC treated here as a 14.3 SEER2-equivalent system. The unit is being evaluated for a three-zone ductless mini-split retrofit — a common approach in triple-deckers and older multi-family buildings that lack ductwork. Eversource's residential electricity rate is roughly 28.82¢/kWh, the highest of any state in this case-study set.
The systems
The comparison is a three-zone, cold-climate-rated ductless mini-split system (roughly 2.5 tons of combined capacity, installed around $11,500) against replacing the oil furnace and window AC in kind (installed around $7,900, reflecting the lower cost of a smaller oil system typical for a condo unit). The ductless system's cold-climate compressor holds up reasonably well in Boston's winters, with an estimated seasonal COP of 2.47 — comparable to Atlanta's result despite Boston being far colder, because cold-climate-rated equipment is specifically engineered to hold efficiency at low temperatures.
The 10-year math
Even with a respectable seasonal COP, Massachusetts' electricity rate — nearly double Georgia's — erases the efficiency advantage the ductless system would otherwise convert into savings.
| Cost category | Cold-Climate Ductless Mini-Split | Oil Furnace + AC |
|---|---|---|
| Equipment + install | $11,500 | $7,900 |
| Heating energy (10 yr) | $23,129 | $20,489 |
| Cooling energy (10 yr) | $5,167 | $5,420 |
| Maintenance (10 yr) | $1,750 | $2,250 |
| 10-year total | $41,546 | $36,058 |
A cold-climate mini-split with a 2.47 seasonal COP should beat oil heat on efficiency alone. It doesn't, because Massachusetts electricity costs nearly twice what Georgia's does — the same equipment, a different utility bill entirely.
The verdict
The oil furnace saves an estimated $5,488 over 10 years. This is one of the clearest illustrations on this site of why electricity price — not just equipment efficiency — decides these comparisons. Eversource's 28.82¢/kWh rate means every kWh the mini-split consumes costs nearly double what the same kWh would cost in Georgia or Washington, and that gap outweighs the mini-split's real efficiency advantage over an oil furnace.
What could change this
This case is genuinely sensitive to policy and program changes. Massachusetts runs some of the most aggressive heat pump incentive programs in the country through Mass Save — a substantial rebate (see the Incentives page) could close or reverse this gap by cutting the install-cost side significantly. A time-of-use electricity plan with cheap overnight rates would also help, since much of a Boston winter's heating load falls overnight. Absent an incentive, rising oil prices are the other lever that would flip this toward the heat pump.
Run it with your own numbers
These figures use representative home sizing and each state's EIA-reported energy prices as of August 2026 — see the methodology page for the full model. To see how your actual square footage, equipment, and utility rate change the outcome, run the Heat Pump vs. Traditional HVAC calculator with your own ZIP code.