Should Key West switch to a heat pump?
Key West is a clear case: a heat pump beats what you have by a wide margin. $1,000 is what Key West 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. Key West's residents would see roughly $369 a year back in running costs, putting the payback around 2.7 years. Nothing about that conclusion is generic — it's built entirely from Key West's own numbers.
Why Key West's climate drives this number
7 heating degree days pile up here every year, so Key West barely has a winter to speak of; the cooling side runs to 5375 cooling degree days, where summers are severe enough that cooling can dominate the annual bill. The 99% winter design temperature here — the cold snap equipment must be sized for, not the seasonal average — is 57.9°F, against a record low of 55°F. That puts the seasonal coefficient of performance at 3.93 for the recommended standard unit. A standard ducted system is enough here; Key West's design temperature doesn't justify the cold-climate premium. Source: NOAA station KEY WEST INTERNATIONAL AIRPOR, 1.4 miles from Key West — the closest one on record.
Key West's running-cost comparison, in dollars
Electricity use for heating alone comes out to about 5 kWh a year on the 2000-square-foot reference house; folding in cooling puts the electric bill near $708 a year. Key West's gas rate of 25.48 per Mcf, applied to the 0 Mcf a year the furnace burns, puts its running cost near $1,077 a year, against 15.43¢ per kWh for electricity. Buy it outright, not incrementally, and payback stretches to 29.8 years; over 15 years the net position sits $4,533 ahead.
The other scenario: no gas furnace to begin with
Plenty of homes in Key West heat with electricity alone, no gas line involved. Swap the comparison to resistance heat instead of gas, and Key West's answer improves. The saving here runs about $370 a year, which recovers the extra $5,500 spent going electric in roughly 14.9 years.
Key West against the rest of the country
Ranked against the other 3206 cities covered, Key West comes in at 3205 for heating severity — 1 would be the coldest place in the dataset — and 1589 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.
Deciding what's next in Key West, FL
About 25,240 people live in Key West, Florida, 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, it's worth getting quotes before your current system fails, not after.
Ask a local HVAC contractor for a quote before committing either way.
More on how this number was built
The methodology guide walks through exactly how Key West's 3.93 seasonal COP and the rest of this page's numbers get built. See what Key West's figure looks like without the $2,000 federal credit in the guide to how that credit moves the payback window.