Pennsylvania · NOAA station KPHL
Heating with a mini-split in Philadelphia, PA
The short answer
In Philadelphia, a median ENERGY STAR cold-climate mini-split heating a 24,000 BTU/h design load should cost about $1,191 a year: $428 more than natural gas (90% efficient), and 63% less than electric resistance. The 99% design temperature is 19°F, so capacity at 5°F rarely decides anything here.
The winter you are actually buying for
This is Philadelphia's average year of hourly temperatures from 2015 through 2024 (87,632 readings at Philadelphia International Airport, 100% of all hours). The dashed line is the 99% design temperature: only 1% of hours are colder.
What it costs, by fuel
Mini-split modeled as a median certified cold-climate unit sized to cover the load at 19°F. Seasonal efficiency in Philadelphia's weather: COP 2.69. In 104 hours a year the load exceeds capacity and the estimate adds electric backup.
Three house sizes
| Design load | Heat pump | Gas | Oil | Propane | Resistance | Seasonal COP | Systems that cover it |
|---|---|---|---|---|---|---|---|
| 12,000 BTU/h | $596 | $382 | $732 | $838 | $1,601 | 2.69 | 11,012 of 14,941 |
| 24,000 BTU/h | $1,191 | $764 | $1,464 | $1,676 | $3,203 | 2.69 | 5,600 of 14,941 |
| 36,000 BTU/h | $1,787 | $1,146 | $2,196 | $2,514 | $4,804 | 2.69 | 2,869 of 14,941 |
The last column counts ENERGY STAR cold-climate systems whose published 5°F and 47°F capacities, joined by a straight line, still reach the design load at Philadelphia's 19°F. How sizing works.
Not a quote. Real bills depend on insulation, thermostat habits, installation and your own Manual J. Use this to decide whether a heat pump is worth pricing, then get two local quotes.
Questions people ask
Will a mini-split work in Philadelphia in winter?
Yes, if it is a cold-climate model. Philadelphia's 99% design temperature from 2015–2024 hourly data is 19°F, and the lowest hour recorded was 2°F. The median ENERGY STAR cold-climate unit keeps 88% of its 47°F heating capacity at 5°F. Hours per year at or below 5°F in Philadelphia: 1.
Is a heat pump cheaper than natural gas in Philadelphia?
At a 24,000 BTU/h design load, we estimate $1,191 a year with a median cold-climate mini-split versus $764 for natural gas at 90% efficiency, using 20.86¢/kWh electricity and 2024 Pennsylvania fuel prices. That is $428 more than natural gas.
How big a mini-split do I need in Philadelphia?
Size to your home's heat loss at 19°F, not to square feet. For a 24,000 BTU/h load, a unit shaped like the median certified system needs about 26,025 BTU/h of 47°F capacity. 5,600 of the 14,941 certified systems cover that load at 19°F.