Should O'Fallon switch to a heat pump?

O'Fallon is a place where a heat pump genuinely costs more to operate than the alternative. 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). Unfortunately the electric bill outweighs the gas bill it replaces by about $74 a year here, so the extra spend stays unrecovered. There's no spin on that: O'Fallon's numbers say wait.

Why O'Fallon's climate drives this number

3677 heating degree days pile up here every year, so O'Fallon has a real but manageable winter; the cooling side runs to 1640 cooling degree days, where summers are hot enough that cooling matters as much as heating. The 99% winter design temperature here — the cold snap equipment must be sized for, not the seasonal average — is 2.5°F, against a record low of -3.8°F. That puts the seasonal coefficient of performance at 2.76 for the recommended cold-climate unit. O'Fallon needs the cold-climate class of unit: past a 25°F design temperature a standard heat pump falls back on resistance backup often enough to eat the savings. Source: NOAA station SCOTT AIR FORCE BASE/MIDAMERI, 4.9 miles from O'Fallon — the closest one on record.

O'Fallon's running-cost comparison, in dollars

Electricity use for heating alone comes out to about 3,373 kWh a year on the 2000-square-foot reference house; folding in cooling puts the electric bill near $909 a year. That compares with roughly 38 Mcf a year of gas at O'Fallon's 11.25 per-Mcf rate — about $836 a year — against a local electricity rate of 19.06¢/kWh. Looked at as a full purchase rather than an incremental one, payback here is longer than the 15-year equipment life, leaving the 15-year total $4,604 behind.

Electric resistance heat in O'Fallon, compared

Plenty of homes in O'Fallon heat with electricity alone, no gas line involved. Swap the comparison to resistance heat instead of gas, and O'Fallon's answer improves. Switching saves about $1,270 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 6.3 years.

Where O'Fallon ranks in this dataset

Ranked against the other 3206 cities covered, O'Fallon comes in at 1697 for heating severity — 1 would be the coldest place in the dataset — and 1270 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 O'Fallon

About 32,169 people live in O'Fallon, Illinois, and every number on this page is what a contractor would actually work from when quoting a system here — the point isn't to replace that quote, it's to tell you whether to bother asking for one. Here, there's no cost penalty to waiting until your current furnace or AC actually needs replacing.

Line up a few local HVAC quotes before you decide.

Reading further on this page's numbers

The methodology guide walks through exactly how O'Fallon's 2.76 seasonal COP and the rest of this page's numbers get built. O'Fallon's 2.5°F design temperature falls on the cold side of the 25°F cutoff the cold-climate unit guide walks through.