Heat Pump Payback in Millbrae, CA
Millbrae, CA: the heat pump payback math
Here in Millbrae, the honest answer is that a heat pump raises your annual running cost. Against a like-for-like gas furnace and AC swap, going electric costs $3,000 more up front here. Unfortunately the electric bill outweighs the gas bill it replaces by about $30 a year here, so the extra spend stays unrecovered. That's Millbrae's own climate and rates talking, not a hedge or a caveat.
Checking a different city
This runs the same numbers for 3206 US cities, not just Millbrae. Look one up here.
How cold Millbrae actually gets
2665 heating degree days pile up here every year, so Millbrae has a mild winter by US standards; the cooling side runs to 90 cooling degree days, where summers rarely ask much of an air conditioner. 39.9°F is the figure equipment gets sized against here, the 99th-percentile cold snap, not an average day, with a low of 35.1°F in the 2024 station record. Worked through the model, that's a seasonal COP of 3.39 on the standard unit fit for this climate. Millbrae's winters don't get cold enough to need the cold-climate premium, a standard unit holds up fine. These numbers come from San Francisco International A, the closest NOAA station, 2.5 miles out.
Millbrae'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. That compares with roughly 28 Mcf a year of gas at Millbrae's $22.01 per-Mcf rate, about $649 a year with the old AC included, against a local electricity rate of 32.83¢/kWh. Because the heat pump costs more to run here, the gap only widens with time: $3,443 behind after 15 years compared with replacing the furnace and AC like-for-like.
The break-even point in Millbrae
For the verdict in Millbrae to flip, electricity would need to drop to about 31.3¢/kWh from 32.83¢, or gas climb past $23.07 per Mcf from $22.01. A utility offering a lower heat pump rate can change this. Until then, no quote price makes a heat pump pay back against gas in Millbrae; the case for one here rests on comfort, cooling, or replacing electric heat instead.
If your home heats with electric baseboard instead of gas
Plenty of homes in Millbrae 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. The saving here runs about $1,575 a year, which recovers the extra $7,500 spent going electric in roughly 4.8 years.
How Millbrae compares nationally
Ranked against the other 3206 cities covered, Millbrae comes in at 2062 for heating severity, 1 would be the coldest place in the dataset, and 1697 by population, where 1 is largest. That's the middle third for winter severity among the cities covered here.
Deciding what's next in Millbrae, CA
Millbrae, California is home to about 23,321 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 Millbrae, nothing is lost by holding off until the current equipment genuinely fails.
Get quotes from local HVAC contractors before deciding.
Where Millbrae's figure comes from
Every constant behind this page, the 3.39 seasonal COP, the degree-day corrections, the equipment costs, is documented in the methodology guide. Millbrae is one of the cities where running costs land higher every year, not just slower to pay back, the guide to where this happens lays out why.