How long does an HVAC system last?

Every machine, both publishers

Fixr's furnace guide adds two exceptions: oil furnaces can last up to 25 years and an electric furnace can last 20 to 30 years with good maintenance. What each of those costs to buy is on our oil furnace page and electric furnace page.

Where they disagree, and it is always the same edge

Look at the two disagreements. On furnaces, This Old House runs five years longer at the top. On air conditioners, Fixr runs five years shorter at the bottom.

Our reading, marked as ours. Neither gap is about the equipment. Both are about the sentence attached to the number. This Old House writes that air conditioners last 15 to 20 years "when properly maintained". Fixr's 10 to 20 has no such condition and reports an average of 15 inside it.

So the two are compatible: 10 to 20 is what happens, and 15 to 20 is what happens if you keep the service up. The shorter bottom end is the un-maintained case, and our maintenance page has what keeping it up actually costs.

We would plan on the lower figure and treat the upper one as the reward for the annual visit, rather than as the expectation.

Who told them

This is the part we always check, and both numbers have a named source worth knowing about.

This Old House attributes the furnace figure to the International Association of Certified Home Inspectors. Home inspectors do not sell furnaces, which makes that a more disinterested source than most in this section. It is still a trade body, and its members have a professional interest in houses needing inspection, but not in this particular sale.

Its heat pump figure is attributed to "local installers", unnamed. Installers sell replacements. We are not saying the figure is wrong, and Fixr's 10 to 15 brackets it from the shorter side, which is the opposite of what an interested party would push. We flag it because an unnamed interested source is exactly what we flag everywhere else in this section, including the trade association behind the highest figure on our duct cleaning page.

And one publisher disagrees with itself

Fixr's heat pump guide says heat pumps last 10 to 15 years. Fixr's geothermal guide, updated six days earlier, prints a comparison table giving an air-source heat pump 10 to 25 years.

That is a ten-year gap between two pages of the same publisher, about the same machine, in the same month. We cannot reconcile it and neither page mentions the other.

Our conclusion: we use 10 to 15, because This Old House's roughly 15 years sits inside it and nothing supports the 25. This is the same approach we take wherever a publisher contradicts itself, and in this section it has most often been This Old House, as our whole system page and heat pump vs furnace page show. It is worth recording that Fixr does it too.

The components do not last as long as the machine

Fixr's repair guide gives two component lifespans, and they cut across the table above:

Our arithmetic, marked as ours. A compressor at 10 to 15 years inside an air conditioner expected to last 10 to 20 means the most expensive single part is likely to fail before the machine does. That is not a defect; it is how the numbers sit. Our AC compressor page works through what to do when it happens, and the answer is usually that the repair arrives too late in the machine's life to be worth it.

The blower motor at about 20 years outlives most of the systems it sits in, which is why our blower motor page treats a failed blower on an old system as a signal about the rest of it.

Two rules for when to stop

This Old House publishes the 50% rule:

if a repair costs more than half of what a new model is worth, it's time to consider replacing it

Fixr's air conditioner guide publishes the opposite instinct, and we think it deserves equal weight: some professionals say that as long as the system is still running, you do not need to replace it unless you dramatically increase the SEER rating.

Our reading. These are not in conflict, they answer different questions. The 50% rule answers "something has broken, do I fix it". The Fixr line answers "nothing has broken, should I upgrade anyway", and its answer is no, unless the efficiency gain is large. Our AC repair page works through a third rule, which multiplies the repair cost by the system's age.

What a year of equipment costs

Our arithmetic, marked as ours, and the reason this page exists. Lifespan is only useful next to price. Taking the midpoint of each lifespan and the installed averages from our own cost pages:

A heat pump does the work of a furnace and an air conditioner, which is the argument for it on our heat pump vs furnace page. It also reaches the end of its life about five years before a furnace does, which is the argument against. Both facts are true and most comparisons publish only one of them.

What actually changes the number

Fixr's boiler guide gives the four factors, and they generalise across every machine here: the climate, the type, the brand, and how appropriately it is sized for your home.

That last one is why our sizing page matters more than it looks. An oversized air conditioner short cycles, and This Old House names reduced lifespan through compressor wear as a direct consequence. A machine at the wrong size does not reach the figures in the table above, no matter how well it is serviced.

What we would do with these numbers

1. Find the installation date before anything else. It is usually on the data plate, and it decides every repair-or-replace question on this site.
2. Use the lower end of each range unless you have the service records to justify the upper one.
3. At year 10 on an air conditioner, start pricing the replacement even if nothing is wrong. The compressor is in its failure window and a quote in hand beats a quote in August.
4. Do not replace a working system for efficiency alone unless the SEER gain is large, which is Fixr's own advice. The same test applies to windows, where our replacement page sets surveyed prices against modelled ones. Our SEER rating page explains how to tell a real gain from a change of measuring scale.
5. Check the ground loop separately on a geothermal system. At 50 years and more it outlives several heat pumps, and that is the part you already paid for.

Which machine you are counting the years on is itself a choice, and our furnace vs boiler page sets out why the house usually makes it for you. What a repair costs on the shortest-lived of these machines is on our heat pump repair page. One age signal is not on the data plate at all: if the system still runs R-22, our Freon page explains what that tells you about its remaining life.