South San Francisco, CA: the heat pump payback math
In South San Francisco, a heat pump would cost more to run each year than what you have now. Against a like-for-like gas furnace and AC swap, going electric costs $1,000 more up front here (already netting out a $2,000 tax credit). The heat pump would cost about $30 more a year to run than the furnace it replaces — a premium with no payback. There's no spin on that: South San Francisco's numbers say wait.
Why South San Francisco's climate drives this number
South San Francisco has a mild winter by US standards — 2665 heating degree days a year against a 65°F base — and summers rarely ask much of an air conditioner, at 90 cooling degree days. The 99% winter design temperature here — the cold snap equipment must be sized for, not the seasonal average — is 39.9°F, against a record low of 35.1°F. That puts the seasonal coefficient of performance at 3.39 for the recommended standard unit. A standard ducted system is enough here; South San Francisco's design temperature doesn't justify the cold-climate premium. Climate figures trace to the nearest NOAA station, SAN FRANCISCO INTERNATIONAL A, 2.5 miles from South San Francisco.
South San Francisco's running-cost comparison, in dollars
A 2000-square-foot house here would pull roughly 1,991 heating kilowatt-hours annually on top of cooling, totalling about $679 a year on electricity. South San Francisco's gas rate of 22.01 per Mcf, applied to the 28 Mcf a year the furnace burns, puts its running cost near $649 a year, against 32.83¢ per kWh for electricity. Priced as a standalone purchase rather than against a like-for-like replacement, equipment payback runs past the 15-year equipment life, for a 15-year net position $1,443 behind.
The other scenario: no gas furnace to begin with
Plenty of homes in South San Francisco 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 $1,575 a year comes back this way, enough that the 3.5-year payback clears the $5,500 premium comfortably within the equipment's life.
How South San Francisco compares nationally
South San Francisco lands at position 2058 out of 3206 cities on heating severity (coldest is 1), and 607 out of 3206 by population size (biggest is 1). That's the middle third for winter severity among the cities covered here.
Next step for 64,660 people in South San Francisco
About 64,660 people live in South San Francisco, California, 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.
Get quotes from local HVAC contractors before deciding.
Where South San Francisco's figure comes from
Nothing above is a black box: the methodology guide shows the full arithmetic behind South San Francisco's 3.39 seasonal COP and payback figure. The guide on cities that never pay back covers exactly South San Francisco's situation: a genuinely higher annual running cost, not a slow one.