Heat pump vs. gas furnace in O'Fallon, MO
O'Fallon technically pencils out, but only past the point the equipment would need replacing anyway. $3,500 is what O'Fallon would pay extra to go electric rather than replace the furnace and AC with the same again, once the $2,000 federal credit is applied. Lower bills claw that back: about $219 saved annually, for a payback of roughly 16 years. That's a technicality, not a recommendation, for anyone actually living in O'Fallon.
How cold O'Fallon actually gets
O'Fallon has a real but manageable winter — 3990 heating degree days a year against a 65°F base — and summers are hot enough that cooling matters as much as heating, at 1370 cooling degree days. Sizing runs off the design temperature, not the average day: 0°F here (record low -8°F), which works out to a seasonal COP of 2.7 for the cold-climate class of unit this climate calls for. A cold-climate unit is the right call in O'Fallon — below 25°F design temperature, a standard heat pump leans hard on electric-resistance backup, which erases most of the savings. These numbers come from SPIRIT OF ST LOUIS AIRPORT, the closest NOAA station, 9.1 miles out.
What it actually costs to run, year to year
A 2000-square-foot house here would pull roughly 3,742 heating kilowatt-hours annually on top of cooling, totalling about $630 a year on electricity. O'Fallon's gas rate of 14.94 per Mcf, applied to the 42 Mcf a year the furnace burns, puts its running cost near $849 a year, against 12.83¢ per kWh for electricity. Buy it outright, not incrementally, and payback stretches to 61.7 years; over 15 years the net position sits $220 behind.
If your home heats with electric baseboard instead of gas
Not every home in O'Fallon has gas service. Compared with baseboard or electric-furnace resistance heat, the numbers shift in the heat pump’s favor. Switching saves about $894 a year here — a heat pump moving heat rather than generating it needs far less electricity than resistance coils — so the extra $8,000 spent up front comes back in about 8.9 years.
O'Fallon against the rest of the country
Among 3206 cities, O'Fallon's winter puts it at rank 1511 for severity, while its size puts it at rank 363 for population — 1 in both cases being the extreme. That's the middle third for winter severity among the cities covered here.
Deciding what's next in O'Fallon, MO
O'Fallon, Missouri is home to about 95,355 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 O'Fallon, nothing is lost by holding off until the current equipment genuinely fails.
Get quotes from local HVAC contractors before deciding.
More on how this number was built
Nothing above is a black box: the methodology guide shows the full arithmetic behind O'Fallon's 2.7 seasonal COP and payback figure. At a 0°F design temperature, O'Fallon sits in cold-climate territory; the guide to that class of unit explains why.