Is a heat pump worth it in Johnston?
In Johnston, a heat pump would cost more to run each year than what you have now. Swap a failed furnace and AC for a heat pump rather than buying like-for-like, and the extra cost here runs $3,500 after a $2,000 federal tax credit. Running costs here land $66 a year HIGHER than the furnace it replaces, so that premium is never recovered. There's no spin on that: Johnston's numbers say wait.
The climate behind Johnston's payback figure
Johnston has a cold winter that leans hard on heating equipment — 5300 heating degree days a year against a 65°F base — and summers add a moderate cooling load, at 961 cooling degree days. The 99% winter design temperature here — the cold snap equipment must be sized for, not the seasonal average — is -7.6°F, against a record low of -16.6°F. That puts the seasonal coefficient of performance at 2.52 for the recommended cold-climate unit. Johnston 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. These numbers come from ANKENY REGIONAL AIRPORT, the closest NOAA station, 8.2 miles out.
What it actually costs to run, year to year
Modelled on a typical 2000-square-foot house, the heat pump draws about 5,326 kWh a year to keep it warm, plus cooling, for a combined electric bill near $818 a year. That compares with roughly 55 Mcf a year of gas at Johnston's 10.61 per-Mcf rate — about $751 a year — against a local electricity rate of 13.31¢/kWh. Buy it outright, not incrementally, and payback stretches to beyond the 15-year equipment life; over 15 years the net position sits $4,497 behind.
The other scenario: no gas furnace to begin with
Not every home in Johnston has gas service. Compared with baseboard or electric-furnace resistance heat, the numbers shift in the heat pump’s favor. About $1,134 a year comes back this way, enough that the 7.1-year payback clears the $8,000 premium comfortably within the equipment's life.
Where Johnston ranks in this dataset
Johnston lands at position 484 out of 3206 cities on heating severity (coldest is 1), and 1606 out of 3206 by population size (biggest is 1). That's the coldest third of the dataset, where climate does most of the work behind this figure.
What to do with this number in Johnston
About 25,022 people live in Johnston, Iowa, 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.
Get quotes from local HVAC contractors before deciding.
Reading further on this page's numbers
The methodology guide walks through exactly how Johnston's 2.52 seasonal COP and the rest of this page's numbers get built. At a -7.6°F design temperature, Johnston sits in cold-climate territory; the guide to that class of unit explains why.