Will a heat pump pay off in La Vergne, TN?
La Vergne technically pencils out, but only past the point the equipment would need replacing anyway. $3,500 is what La Vergne 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. La Vergne's residents would see roughly $108 a year back in running costs, putting the payback around 32.5 years. La Vergne's own numbers say this pencils out only in theory, not in practice.
The climate behind La Vergne's payback figure
3001 heating degree days pile up here every year, so La Vergne has a real but manageable winter; the cooling side runs to 1705 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 7°F, against a record low of -7.6°F. That puts the seasonal coefficient of performance at 2.87 for the recommended cold-climate unit. La Vergne 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 SMYRNA AIRPORT, 2.4 miles from La Vergne — the closest one on record.
What it actually costs to run, year to year
Modelled on a typical 2000-square-foot house, the heat pump draws about 2,648 kWh a year to keep it warm, plus cooling, for a combined electric bill near $569 a year. La Vergne's gas rate of 11.84 per Mcf, applied to the 31 Mcf a year the furnace burns, puts its running cost near $677 a year, against 13.87¢ per kWh for electricity. Priced as a standalone purchase rather than against a like-for-like replacement, equipment payback runs about 125.4 years, for a 15-year net position $1,885 behind.
The other scenario: no gas furnace to begin with
Plenty of homes in La Vergne heat with electricity alone, no gas line involved. Against electric-resistance heat — baseboard or an electric furnace, both 100% efficient but still just resistance — the case for switching gets stronger here. About $792 a year comes back this way, enough that the 10.1-year payback clears the $8,000 premium comfortably within the equipment's life.
La Vergne against the rest of the country
La Vergne lands at position 1932 out of 3206 cities on heating severity (coldest is 1), and 988 out of 3206 by population size (biggest is 1). That's the middle third for winter severity among the cities covered here.
What to do with this number in La Vergne
About 41,430 people live in La Vergne, Tennessee, 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.
Ask a local HVAC contractor for a quote before committing either way.
Reading further on this page's numbers
Nothing above is a black box: the methodology guide shows the full arithmetic behind La Vergne's 2.87 seasonal COP and payback figure. La Vergne's 7°F design temperature falls on the cold side of the 25°F cutoff the cold-climate unit guide walks through.