Should Marathon switch to a heat pump?
The math in Marathon isn't close — a heat pump wins outright. Swap a failed furnace and AC for a heat pump rather than buying like-for-like, and the extra cost here runs $1,000 after a $2,000 federal tax credit. That premium is recovered through $340 of lower running costs every year, landing the payback clock at roughly 2.9 years. That verdict holds specifically for Marathon's own climate and rates, not a national average.
How cold Marathon actually gets
Degree days tell the story here: Marathon racks up 12 heating degree days each year (base 65°F), and summers are severe enough that cooling can dominate the annual bill, with 4935 cooling degree days on the cooling side. Sizing runs off the design temperature, not the average day: 59.9°F here (record low 59°F), which works out to a seasonal COP of 3.99 for the standard class of unit this climate calls for. Marathon's winters don't get cold enough to need the cold-climate premium — a standard unit holds up fine. Climate figures trace to the nearest NOAA station, VACA KEY, 4.8 miles from Marathon.
What it actually costs to run, year to year
Electricity use for heating alone comes out to about 8 kWh a year on the 2000-square-foot reference house; folding in cooling puts the electric bill near $650 a year. Marathon's gas rate of 25.48 per Mcf, applied to the 0 Mcf a year the furnace burns, puts its running cost near $990 a year, against 15.43¢ per kWh for electricity. Looked at as a full purchase rather than an incremental one, payback here is roughly 32.4 years, leaving the 15-year total $4,094 ahead.
The other scenario: no gas furnace to begin with
Gas isn't universal in Marathon — many houses run on electric heat already. Against electric-resistance heat — baseboard or an electric furnace, both 100% efficient but still just resistance — the case for switching gets stronger here. About $341 a year comes back this way, enough that the 16.1-year payback clears the $5,500 premium comfortably within the equipment's life.
Where Marathon ranks in this dataset
Among 3206 cities, Marathon's winter puts it at rank 3204 for severity, while its size puts it at rank 3197 for population — 1 in both cases being the extreme. That's the mildest third of cities covered, where utility rates carry more of the answer than climate does.
Deciding what's next in Marathon, FL
Marathon, Florida is home to about 10,039 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. Given the math above, Marathon is a place worth lining up quotes ahead of a breakdown, not waiting for one.
Line up a few local HVAC quotes before you decide.
Reading further on this page's numbers
Nothing above is a black box: the methodology guide shows the full arithmetic behind Marathon's 3.99 seasonal COP and payback figure. The $2,000 federal credit baked into Marathon's number is explained, with the before-and-after math, in the tax credit guide.