Heat Pump Payback in San Marcos, CA
Should San Marcos switch to a heat pump?
San Marcos technically pencils out, but only past the point the equipment would need replacing anyway. $3,000 is what San Marcos would pay extra to go electric rather than replace the furnace and AC with the same again. San Marcos's residents would see roughly $88 a year back in running costs, putting the payback around 34 years. That's a technicality, not a recommendation, for anyone actually living in San Marcos.
Not the city you meant?
This runs the same numbers for 3206 US cities, not just San Marcos. Look one up here.
San Marcos's weather, in the numbers that matter
Degree days tell the story here: San Marcos racks up 3833 heating degree days each year (base 65°F), and summers are hot enough that cooling matters as much as heating, with 1587 cooling degree days on the cooling side. The 99% winter design temperature here, the cold snap equipment must be sized for, not the seasonal average, is 30.9°F, and the coldest daily reading in the 2024 station record was 28.9°F. That puts the seasonal coefficient of performance at 3.12 for the recommended standard unit. San Marcos's winters don't get cold enough to need the cold-climate premium, a standard unit holds up fine. These numbers come from Marine Corps Air Station, the closest NOAA station, 5.4 miles out.
The yearly running costs in San Marcos
Modelled on a typical 2000-square-foot house, the heat pump draws about 3,111 kWh a year to keep it warm, plus cooling, for a combined electric bill near $1,466 a year. The gas furnace it replaces burns roughly 40 Mcf a year at $22.01 per Mcf here, for a running cost near $1,554 a year including the old AC (electricity here runs 32.83¢/kWh). If the current system still worked and you replaced it anyway, the full cost would take longer than the 15-year equipment life to earn back; against buying a new furnace and AC regardless, the 15-year total lands $1,675 behind.
What would change San Marcos's answer
Gas would only overtake the heat pump in San Marcos if electricity rose past 36.5¢/kWh from 32.83¢, or gas fell under $19.80 per Mcf from $22.01. A useful quote test for San Marcos: the heat pump is worth it within a decade if it costs less than $880 more than replacing the furnace and AC, and within 7 years if the gap is under $616.
The other scenario: no gas furnace to begin with
Not every home in San Marcos has gas service. Compared with baseboard or electric-furnace resistance heat, the numbers shift in the heat pump’s favor. About $2,396 a year comes back this way, enough that the 3.1-year payback clears the $7,500 premium comfortably within the equipment's life.
Where San Marcos ranks in this dataset
Ranked against the other 3206 cities covered, San Marcos comes in at 1619 for heating severity, 1 would be the coldest place in the dataset, and 354 by population, where 1 is largest. That's the middle third for winter severity among the cities covered here.
Deciding what's next in San Marcos, CA
San Marcos, California is home to about 96,620 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 San Marcos, nothing is lost by holding off until the current equipment genuinely fails.
Ask a local HVAC contractor for a quote before committing either way.
Where San Marcos's figure comes from
Nothing above is a black box: the methodology guide shows the full arithmetic behind San Marcos's 3.12 seasonal COP and payback figure. San Marcos technically clears a payback on paper, just past the equipment's own working life, the no-payback guide explains why that distinction matters.