Furnace replacement in San Mateo County
Replacing your furnace? Start here.
Replacing a furnace in San Mateo takes a permit that the city can often approve over the counter. Whether you go back to gas or switch to a heat pump depends on your city, and the Energy Code adds a duct test and some paperwork. All of that is below.
What a furnace replacement involves
A replacement is more than swapping one box for another. Here is the job, start to finish.
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We look at the house first
The old furnace, the ducts, the venting, the gas line and the rooms that run hot or cold. The new furnace is sized for the house, not copied from the old label.
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You choose what goes in
A new gas furnace, or a heat pump if you're thinking of going electric. We'll talk through what each means for your house and the rules in your city.
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Out with the old
Gas, power and venting are shut off and disconnected, and the old furnace comes out.
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In with the new
The new furnace is set and connected to the gas line, the venting, the ducts and the thermostat.
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We fire it up and check it
It runs through a full heating cycle while we check the burners, the venting and the air coming out of the vents.
Do I need a permit to replace a furnace in San Mateo?
Yes. The City of San Mateo's Building Division lists a furnace replaced or installed in the same location among the mechanical permits it can approve over the counter, so a like-for-like swap doesn't have to wait on plan review.
If the furnace moves, or you are changing what heats the house, that is a bigger job with a different conversation. Other cities have their own steps, and our permit guide sets them out.
Source: City of San Mateo Building Division FAQ, checked 2026-10-17
Can I still install a new gas furnace?
In most of our area, yes. A few cities have started steering replacements toward heat pumps, and the choice depends on where you live:
Menlo Park allows either a new gas furnace or a heat pump space heater. Portola Valley allows like-for-like replacement and only encourages a heat pump. Their own words are below.
Elsewhere, ask us before you buy. We'll tell you what your city allows and what each option involves, so you aren't surprised at inspection.
Source: City of Menlo Park, Furnace/Air Conditioner Replacement Submittal Requirements, checked 2026-10-17
What does the Energy Code require on a furnace change-out?
There are a test and a form to plan for. The test is the duct test. If the change-out includes a new air handler, an outdoor unit or a coil, the connected ducts have to be sealed by the installer and checked by an independent rater. A new furnace and a new AC often go in together, so this comes up more often than you would think.
The form is the paperwork. The state has simplified the permit process for HVAC change-outs: the energy form can be handed in at final inspection and not before the permit is issued.
Source: California Energy Commission, 2025 Single-Family Residential Compliance Manual (June 2025), checked 2026-10-17
Replacing a furnace?
Call and tell us what you have now, or book a visit online.
Does the Air District's rule affect my replacement?
It can. The Bay Area Air District's zero-NOx rule for gas furnaces applies when existing equipment burns out and is replaced. It has a 2029 compliance date and is under review, so the date may still change. It does not force removal of a working furnace.
One more state rule to know: a replacement heating system can't use electric resistance as its main heat source, except in the narrow cases the Energy Code lists. That rules out a plain electric furnace as a swap.
Source: Bay Area Air Quality Management District, Rules 9-4 and 9-6 Building Appliances, checked 2026-10-17
Tell us what it's doing. We'll take it from there.
Call and describe the problem: the noise, the smell, the room that never warms up. Or book a visit online.
