Repair or Replace a Furnace or AC: When It Is Time

By Ray Bennett · Updated 2 October 2026 · 5 min read · Checked against the sources at the end

Repair or Replace a Furnace or AC: When It Is Time

Short answer

ENERGY STAR's line is 10 years for a heat pump or air conditioner and 15 for a furnace or boiler. Past that, with repeat problems, costly repairs and rising bills, it is worth weighing a replacement. ENERGY STAR's own table says that if two or more of its replace signs apply, it is probably time. Younger, with a good record and a small fix, repair it.

When a furnace or air conditioner breaks, the quick repair is tempting. ENERGY STAR’s own advice is to weigh more than the bill in front of you: the system’s age, its overall condition, its efficiency, and the energy and repair costs to come.

This page sets out ENERGY STAR’s checklist and its repair or replace table. It also shows which of its signs can point at the ducts or the thermostat rather than the machine.

Before you start

What to carry: a torch, a pen and your last year of energy bills. Ten minutes to find the age.

Gas or electric? Both, but the line differs. ENERGY STAR uses 10 years for a heat pump or air conditioner, and 15 years for a furnace or boiler. The age is on each unit’s plate: how old is my furnace or AC.

Find the age. The installation paperwork or the company that services the system can tell you when it went in.

Some faults decide it for you. A cracked heat exchanger. On a furnace it can let combustion gases into the air, and the answer is a new furnace: a cracked heat exchanger.

A failed compressor. On an older air conditioner or heat pump, it usually means a new system.

Whichever you choose. ENERGY STAR says to make sure a professional contractor does the complete job, because only a proper installation delivers the efficiency you paid for.

ENERGY STAR’s repair or replace table

ENERGY STAR's own table. Two or more in the right column, and it says it is probably time to consider a replacement.

Check 1

Count the replace signs

The rule. ENERGY STAR says that if two or more items apply to you in the replace column, it is probably time to consider a new, ENERGY STAR certified system.

Keep repairing if. It is under 10 years old, or under 15 for a furnace or boiler. It has a good service record, a major repair was made recently and only a minor one is needed, the on and off cycling is not excessive, it performs as expected, or you are moving soon.

Time to replace if. It is over 10 years old, or over 15 for a furnace or boiler. It has had repeat problems, it needs extensive or costly repairs, the cycling seems excessive, it is not performing as expected, or you are staying in the home a long time.

Keep repairing if	Time to replace if
Under 10 years old, under 15 for a furnace or boiler	Over 10 years old, over 15 for a furnace or boiler
A good service record	Repeat problems
A major repair made recently, only a minor one needed	Extensive or costly repairs needed
On and off cycling not excessive	On and off cycling seems excessive
Performing as expected	Not performing as expected
Moving soon	Staying in the home a long time

The signs ENERGY STAR lists

ENERGY STAR's age marks, and what it says a certified replacement saves.

Check 2

Go down the list

A heat pump or air conditioner over 10 years old. ENERGY STAR says a certified unit, installed correctly, can save up to 20 percent on heating and cooling costs. What the ratings on a new one mean: SEER2 and the 2023 minimums.

A furnace or boiler over 15 years old. ENERGY STAR says a certified furnace is 15 percent more efficient than a conventional one, and a certified boiler 5 percent more efficient than a new standard model.

Frequent repairs and rising bills. ENERGY STAR says the equipment may have become less efficient.

A noisy system. ENERGY STAR names an undersized duct system or a problem with the indoor coil of the cooling equipment: evaporator coil problems.

When the sign is not the machine

Check 3

Rule out the house first

Rooms too hot or too cold. ENERGY STAR says the cause can be the equipment, but also duct problems or poor insulation: one room hotter or colder than the rest.

Humidity problems. ENERGY STAR lists poor equipment operation, the wrong equipment, and leaky ductwork, which can leave the air too dry in winter or too humid in summer.

Too much dust. ENERGY STAR says leaky ducts can pull dust from attics, crawl spaces and basements through the house, and that sealing them may be the answer: leaky ductwork.

Nobody home all day. ENERGY STAR’s answer is a programmable thermostat, not new equipment.

If you do replace

Check 4A contractor's quote

Get the installation right

The complete job. ENERGY STAR says only proper installation makes the equipment run at its peak efficiency.

Seal the ducts too. ENERGY STAR says a well designed, sealed duct system may let you choose a smaller, less costly system that also dehumidifies better.

Signs that point to a new system. ENERGY STAR mentions noisy cooling, uneven rooms, excess dust and frequent cycling as signs of an inefficient system worth reviewing with a contractor: how often to service it.

Questions people ask

How old is too old for a furnace?

ENERGY STAR’s mark is 15 years for a furnace or boiler. Past that, with repeat problems or costly repairs, it is worth weighing a replacement.

How old is too old for an air conditioner or heat pump?

ENERGY STAR uses 10 years. It says a certified replacement, installed correctly, can save up to 20 percent on heating and cooling costs.

Should I repair or replace my AC?

Count ENERGY STAR’s replace signs: over 10 years old, repeat problems, costly repairs, excessive cycling, poor performance, staying for years. Two or more, and it says it is probably time.

Is it worth replacing a furnace that still works?

ENERGY STAR suggests considering it past 15 years, especially with rising bills. A certified furnace is 15 percent more efficient than a conventional one.

Could the problem be my ducts instead?

Often. ENERGY STAR ties uneven rooms, humidity trouble and dust to leaky or undersized ducts as well as the equipment.

Should I repair it if I am moving soon?

ENERGY STAR’s table puts moving soon on the repair side, and staying in the home a long time on the replace side.

Sources: ENERGY STAR "When is it time to replace?" and its sample article "Repair or Replace? You Decide.", and the ENERGY STAR Duct Sealing brochure (EPA 430-F-09-050)