Byram, MS: the heat pump payback math
Byram technically pencils out, but only past the point the equipment would need replacing anyway. $3,500 is what Byram 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. Byram's residents would see roughly $219 a year back in running costs, putting the payback around 16 years. Byram's own numbers say this pencils out only in theory, not in practice.
The climate behind Byram's payback figure
1947 heating degree days pile up here every year, so Byram has a mild winter by US standards; the cooling side runs to 1781 cooling degree days, where summers are hot enough that cooling matters as much as heating. 19.4°F is the figure equipment gets sized against here — the 99th-percentile cold snap, not an average day — with a record low of 8.6°F on file. Worked through the model, that's a seasonal COP of 3.17 on the cold-climate unit fit for this climate. Byram 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 JOHN BELL WILLIAMS AIRPORT, the closest NOAA station, 10.6 miles out.
The month-to-month numbers for Byram
Electricity use for heating alone comes out to about 1,555 kWh a year on the 2000-square-foot reference house; folding in cooling puts the electric bill near $476 a year. The gas furnace it replaces burns roughly 20 Mcf a year at 16.64 per Mcf here, for a running cost near $694 a year (electricity here runs 15.47¢/kWh). Buy it outright, not incrementally, and payback stretches to 61.6 years; over 15 years the net position sits $215 behind.
If your home heats with electric baseboard instead of gas
Not every home in Byram has gas service. Against electric-resistance heat — baseboard or an electric furnace, both 100% efficient but still just resistance — the case for switching gets stronger here. The saving here runs about $644 a year, which recovers the extra $8,000 spent going electric in roughly 12.4 years.
Where Byram ranks in this dataset
Ranked against the other 3206 cities covered, Byram comes in at 2451 for heating severity — 1 would be the coldest place in the dataset — and 2705 by population, where 1 is largest. That's the mildest third of cities covered, where utility rates carry more of the answer than climate does.
What to do with this number in Byram
About 12,656 people live in Byram, Mississippi, 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.
More on how this number was built
Every constant behind this page — the 3.17 seasonal COP, the degree-day corrections, the equipment costs — is documented in the methodology guide. At a 19.4°F design temperature, Byram sits in cold-climate territory; the guide to that class of unit explains why.