Philadelphia, PA: the heat pump payback math
The payback math works in Philadelphia on paper, past the equipment's own working life. Against a like-for-like gas furnace and AC swap, going electric costs $3,500 more up front here (already netting out a $2,000 tax credit). That premium is recovered through $80 of lower running costs every year, landing the payback clock at roughly 43.8 years. That's a technicality, not a recommendation, for anyone actually living in Philadelphia.
Philadelphia's weather, in the numbers that matter
Philadelphia has a real but manageable winter — 3879 heating degree days a year against a 65°F base — and summers are hot enough that cooling matters as much as heating, at 1551 cooling degree days. The 99% winter design temperature here — the cold snap equipment must be sized for, not the seasonal average — is 14°F, against a record low of 8.1°F. That puts the seasonal coefficient of performance at 3.04 for the recommended cold-climate unit. A cold-climate unit is the right call in Philadelphia — below 25°F design temperature, a standard heat pump leans hard on electric-resistance backup, which erases most of the savings. Climate figures trace to the nearest NOAA station, NE PHILADELPHIA AIRPORT, 8 miles from Philadelphia.
What it actually costs to run, year to year
Electricity use for heating alone comes out to about 3,231 kWh a year on the 2000-square-foot reference house; folding in cooling puts the electric bill near $945 a year. Philadelphia's gas rate of 15.04 per Mcf, applied to the 40 Mcf a year the furnace burns, puts its running cost near $1,025 a year, against 20.75¢ per kWh for electricity. Priced as a standalone purchase rather than against a like-for-like replacement, equipment payback runs about 169.1 years, for a 15-year net position $2,302 behind.
The other scenario: no gas furnace to begin with
Not every home in Philadelphia has gas service. Compared with baseboard or electric-furnace resistance heat, the numbers shift in the heat pump’s favor. The saving here runs about $1,510 a year, which recovers the extra $8,000 spent going electric in roughly 5.3 years.
Philadelphia against the rest of the country
Ranked against the other 3206 cities covered, Philadelphia comes in at 1604 for heating severity — 1 would be the coldest place in the dataset — and 6 by population, where 1 is largest. That's the middle third for winter severity among the cities covered here.
What to do with this number in Philadelphia
Philadelphia, Pennsylvania is home to about 1,573,916 people, and the figures above are the same ones a local HVAC contractor uses to size and quote a system — this site doesn't guess where a real quote would land, it just tells you whether it's worth asking for one. In Philadelphia, nothing is lost by holding off until the current equipment genuinely fails.
Line up a few local HVAC quotes before you decide.
More on how this number was built
Every constant behind this page — the 3.04 seasonal COP, the degree-day corrections, the equipment costs — is documented in the methodology guide. Philadelphia's 14°F design temperature is below the 25°F line, which is why a cold-climate unit is the right call here — see what that changes in the cold-climate unit guide.