Heat pump vs. gas furnace in South Lyon, MI
South Lyon is a place where a heat pump genuinely costs more to operate than the alternative. $3,500 is what South Lyon 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. Running costs here land $331 a year HIGHER than the furnace it replaces, so that premium is never recovered. That's South Lyon's own climate and rates talking, not a hedge or a caveat.
How cold South Lyon actually gets
5159 heating degree days pile up here every year, so South Lyon has a cold winter that leans hard on heating equipment; the cooling side runs to 837 cooling degree days, where summers add a moderate cooling load. 1°F is the figure equipment gets sized against here — the 99th-percentile cold snap, not an average day — with a record low of -5.1°F on file. Worked through the model, that's a seasonal COP of 2.72 on the cold-climate unit fit for this climate. A cold-climate unit is the right call in South Lyon — below 25°F design temperature, a standard heat pump leans hard on electric-resistance backup, which erases most of the savings. Source: NOAA station WILLOW RUN AIRPORT, 16.9 miles from South Lyon — the closest one on record.
The month-to-month numbers for South Lyon
A 2000-square-foot house here would pull roughly 4,803 heating kilowatt-hours annually on top of cooling, totalling about $1,143 a year on electricity. South Lyon's gas rate of 10.92 per Mcf, applied to the 54 Mcf a year the furnace burns, puts its running cost near $811 a year, against 20.72¢ per kWh for electricity. 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 $8,472 behind.
Electric resistance heat in South Lyon, compared
Not every home in South Lyon 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. About $1,788 a year comes back this way, enough that the 4.5-year payback clears the $8,000 premium comfortably within the equipment's life.
South Lyon against the rest of the country
South Lyon lands at position 586 out of 3206 cities on heating severity (coldest is 1), and 2781 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 South Lyon
South Lyon, Michigan is home to about 12,219 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 South Lyon, nothing is lost by holding off until the current equipment genuinely fails.
Line up a few local HVAC quotes before you decide.
More on how this number was built
Every constant behind this page — the 2.72 seasonal COP, the degree-day corrections, the equipment costs — is documented in the methodology guide. South Lyon's 1°F design temperature falls on the cold side of the 25°F cutoff the cold-climate unit guide walks through.