Nobody replaces a furnace because they want to. They replace it because a repair estimate landed on the kitchen table and the number was bigger than expected, or because the unit is old and the heating season is coming and they would rather decide now than at two in the morning in January. Either way, the decision is not really about the furnace. It is about four questions, and this is how we walk through them with customers.
The four questions
- How old is it, and what has it cost you in the last two years?
- What is actually broken, and is it the heat exchanger?
- What would a new one save you in gas, honestly?
- Would a heat pump make more sense than another furnace, given the rebates?
1. Age and repair history
Most gas furnaces last fifteen to twenty years. Industry service-life data puts the median around eighteen. ENERGY STAR’s own guidance is that a furnace older than fifteen years is worth considering for replacement, not because it will fail on its sixteenth birthday but because the parts that fail from that point on are the expensive ones.
The rule of thumb we use, and it is a rule of thumb rather than a law: if the furnace is over fifteen and the repair estimate is more than a third of the cost of a new one, replacement is usually the better spend. If it is over twenty, we say so plainly and price both, because at twenty a second repair within a year is likely.
What matters more than the age alone is the trend. One igniter in twelve years is a healthy furnace. An igniter, a pressure switch and an inducer motor inside eighteen months is a furnace telling you something. Add up what you have spent on it in the last two winters before you decide.
In the Sacramento area the age question has a local twist. Sun City Roseville’s homes were built between 1995 and 2000, so its original furnaces are all past twenty-five. Most of Elk Grove, Natomas and the newer parts of Rocklin were built 1990 to 2004, which puts those furnaces at twenty-two to thirty-six. If your home is in one of those tracts and the furnace is original, you are not deciding whether to replace it. You are deciding when.
2. What is broken
Some repairs are worth doing on a furnace of any age. Others are the end.
- Worth repairing at any age: igniter, flame sensor, pressure switch, capacitor, thermostat, a clogged condensate trap. These are inexpensive parts and short visits.
- Worth repairing under fifteen years, worth a conversation past it: inducer motor, blower motor, gas valve, control board.
- The end, at any age: a cracked heat exchanger.
The heat exchanger is the metal chamber where the gas burns and the house air picks up heat on the other side. When it cracks, combustion gases, including carbon monoxide, can enter the air stream. Replacing the exchanger is technically possible and on most furnaces costs close to what a new furnace costs, with none of the warranty. We do not repair cracked heat exchangers. We show you the crack, we shut the gas to the unit, and we quote a replacement. That is the one furnace repair we turn down, and we explain why on every visit where it comes up.
If your furnace is short cycling, banging at startup, or blowing cold air, those are usually not end-of-life signs. Read our guides to a furnace that keeps turning on and off, furnace noises and a furnace blowing cold air before assuming the worst.
3. What a new furnace actually saves
Here is the honest version. A furnace from the 1990s is typically rated around 80% AFUE, meaning 80 cents of every gas dollar becomes heat in the house. A new high-efficiency condensing furnace is rated 95% or higher. Moving from one to the other cuts gas use for heating by roughly fifteen to thirty percent, depending on how leaky the ducts are and how well the house holds heat.
Before assuming the furnace is the reason for a high bill, read why a heating bill is so high. Ducts and insulation are usually ahead of it.
The catch is that Sacramento winters are short and mild. A furnace here runs a fraction of the hours it would in Minneapolis. So the gas savings on their own rarely pay for a furnace in under ten years. That is why we tell people not to replace a working furnace for efficiency alone. Replace it when it is failing, and then choose the efficient one, because at that point the efficiency is close to free. Our article on furnace brands goes into why premium AFUE rarely pays off here and what does.
The savings that do matter in this climate are in the ducts. A 1960s ranch home in Carmichael or Citrus Heights with original ductwork can be losing a quarter of its heated air into the attic or crawlspace. Sealing that is often a better use of money than a higher AFUE number, and we test for it before quoting a furnace.
4. Furnace or heat pump
This is the question that has changed in the last few years. A heat pump heats and cools with the same equipment, runs on electricity, and in a climate like Sacramento’s, where winter lows sit in the high 30s, it heats efficiently without a gas backup.
We go through the whole comparison, including the cases where gas still wins, in our guide to heat pump vs furnace in Sacramento.
What makes it a real option here rather than a talking point is SMUD. If you are in SMUD territory, which covers Sacramento, Elk Grove, Citrus Heights, Carmichael, Rancho Cordova and Folsom’s eastern side, SMUD currently lists $3,000 for a variable-stage heat pump and $2,000 for a two-stage unit when it replaces a gas furnace, plus up to $2,000 toward a panel upgrade if one is needed. The amounts change and the equipment has to go in through a contractor in SMUD’s network, so we confirm the current numbers when we quote. Roseville, Rocklin, Lincoln and Granite Bay are on Roseville Electric or PG&E, where the picture is different.
The City of Sacramento has also adopted a strategy to move existing buildings off gas by 2045. It imposes no requirement on you today. But if you are replacing a furnace in the city in 2026, it is worth knowing which direction the rules are moving.
When we quote a replacement in SMUD territory we quote a furnace and a heat pump side by side, with the rebate applied, and we tell you which one we would choose for our own house. Details on the heat pump side are on our heat pump installation in Sacramento page and our guide to heat pump brands.
The signs that mean decide this season, not next
- The furnace is over twenty years old and has needed a repair in each of the last two winters.
- Rooms that used to be warm are not, and the ducts have been checked.
- The gas bill has climbed with no change in how you use the house.
- Yellow burner flames instead of blue, soot on the cabinet, or a carbon monoxide alarm. Stop using it and call.
- The heat exchanger has been flagged by anyone, ever.
What we do
Our diagnostic is a flat $69, credited toward whatever you decide. If the furnace can be repaired sensibly, we repair it and tell you what to expect next. If it cannot, we give you the replacement numbers, furnace and heat pump, with the rebates applied, and we do not push. Same-day service in Roseville, Rocklin, Sacramento, Citrus Heights, Folsom and Elk Grove. See furnace repair in Roseville, furnace repair in Sacramento, and furnace installation in Sacramento for what the replacement side looks like. We also have dedicated pages for Rocklin, Folsom, Elk Grove and Citrus Heights.
Frequently asked questions
How long does a gas furnace last?
Fifteen to twenty years for most units, with industry data putting the median around eighteen. ENERGY STAR suggests considering replacement once a furnace passes fifteen, because the repairs that follow tend to be the expensive ones.
Should I repair or replace a furnace that is 15 years old?
It depends on what is broken. An igniter or flame sensor is worth repairing at any age. A blower motor or control board at fifteen is a conversation. A cracked heat exchanger is a replacement at any age. Our rule of thumb: over fifteen and a repair more than a third of a new unit, replace.
Can a cracked heat exchanger be repaired?
Technically yes, but replacing the exchanger costs close to a new furnace and carries none of the warranty, so we do not do it. We show you the crack, shut the gas to the unit, and quote a replacement.
Will a new furnace lower my gas bill?
Yes, by roughly fifteen to thirty percent of your heating gas if you move from an 80% unit to a 95% one. But Sacramento winters are short, so the savings alone rarely pay for the furnace quickly. Replace it when it is failing, and choose the efficient one at that point.
Is a heat pump better than a furnace in Sacramento?
Often, yes, especially in SMUD territory where rebates of $2,000 to $3,000 currently apply to a heat pump replacing a gas furnace. Sacramento winters are mild enough that a heat pump heats efficiently without gas backup. We quote both side by side so you can compare.