Heating and air conditioning: when to repair and when to replace

When the air conditioning quits in July or the furnace won’t start in January, the house becomes hard to live in, especially for children and older relatives. This guide is for you if you own your home and your heating or cooling equipment is failing, costing a lot or getting old. It explains when to think about replacing it, what upkeep ENERGY STAR recommends, how to hire a technician and what public help exists if your income is low.

Age of an AC or heat pump at which the DOE says to think about replacing it

10 years¹

The same for a furnace or boiler

15 years¹

At a minimum, change the filter, according to ENERGY STAR

Every 3 months³

How much a poor installation can cut efficiency

Up to 30%³

Signs it’s time to think about replacing it

The Department of Energy (DOE) Energy Saver Guide says to consider replacing your system if any of these is true: your heat pump or air conditioner is more than 10 years old; your furnace or boiler is more than 15 years old; the equipment needs frequent repairs and your energy bills are going up; or some rooms in the house are too hot or too cold.¹

Reaching that age doesn’t mean you must replace it today. The DOE also says your contractor should give you information on the safety and cost effectiveness of repair versus replacement, and on the heating and cooling options available.¹ Ask for that information in writing.

ENERGY STAR adds something important: before investing in a new system, fix the big air leaks in the house and the ducts, because sometimes they are the real problem and not the equipment.³ A new air conditioner hooked up to leaky ducts still cools poorly.

The upkeep ENERGY STAR recommends

ENERGY STAR recommends having a contractor do a check-up every year before each season: cooling in the spring and heating in the fall, because contractors get busy in summer and winter.² A good reminder is to do it when the clocks change.

What a typical check-up includes, according to ENERGY STAR

1. 1. Thermostat and electrical connections

   Every year

   Check the thermostat, tighten connections and lubricate moving parts.²

2. 2. Drain and air conditioning coils

   In spring

   Check the condensate drain, clean the coils and measure the refrigerant.²

3. 3. Gas, burner and heat exchanger

   In fall

   On gas or oil equipment: an improperly operating connection is a fire hazard.²

4. 4. The filter

   Every month

   Check it monthly and change it at least every 3 months.³

5. 5. Carbon monoxide alarms

   Always

   On every level of the home and outside sleeping areas.⁶

The filter is the easiest part to care for yourself. ENERGY STAR says to check it every month, especially in winter and summer; if it looks dirty after a month, change it, and at a minimum every 3 months. A dirty filter makes the system work harder and can lead to expensive maintenance or early failure.³

Ducts matter too. According to ENERGY STAR, nearly half the energy used in a home goes to heating and cooling, and sealing and insulating ducts can improve efficiency by as much as 20 percent, and sometimes much more.³

How to hire the technician

ENERGY STAR gives this advice for hiring a heating and cooling contractor: find out your state’s license and insurance requirements; know your system’s model and maintenance history; ask for references from other customers and call them.⁴

The contractor should look over your home carefully. ENERGY STAR says a bigger system isn’t always better, and that size is figured from your house, insulation and windows.⁴ If someone quotes you a price over the phone without seeing the house, get another opinion.

Get written, itemized estimates, and compare cost, efficiency and warranties. Before work starts, sign a written proposal that states the cost, the model numbers, the job schedule and the warranty.⁴ ENERGY STAR also warns that improper installation can cut system efficiency by up to 30 percent.³ The guide to what a repair quote must include helps you check each point.

Repair or replace the equipment

Younger equipment

Repair

• Makes sense if the equipment is under the ages the DOE names and rarely fails.¹
• Ask the contractor about the cost and safety of repair versus replacement.¹
• Check the filter, ducts and air leaks first.³³

Older equipment

Replace

• The DOE says to think about it after 10 years (AC or heat pump) or 15 (furnace or boiler).¹
• The right size matters more than the biggest.⁴
• Sign a proposal with model, cost, dates and warranty.⁴

Get the comparison in writing before you decide.¹⁴

What should happen when the technician visits

A quick visit isn’t enough. ENERGY STAR says the contractor should spend significant time inspecting your current system and your home. A good contractor inspects the ducts, if there are any, for air leaks and insulation, and measures airflow to make sure it meets the manufacturer’s specifications.⁴

If they propose new equipment, ask them to show you the savings calculations: ENERGY STAR says contractors should be able to do that for equipment with its label. It also recommends checking for rebates on certified efficient equipment before you buy.⁴

While the technician works, write down what they find and ask them to put it in the estimate: which part is failing, what they recommend and why. If you get a second opinion later, the other contractor can compare the same problem and not a different one. Keep these notes with your service invoices: they show how many times the equipment has failed, which is one of the signs the DOE names.¹

The heat pump as an option

An air source heat pump heats in winter and cools in summer. ENERGY STAR says that, in most zones, it can go in as a drop-in replacement when the central air conditioner or the furnace needs replacing, and that its cold-climate certification requires performance testing down to 5 °F.⁵ If your winters are very cold, ask the contractor for a model certified for cold climates and whether you need back-up heat. Ask, too, how the new unit will connect to the ducts you already have, and whether they need sealing first, since leaky ducts waste part of what any new system produces.³

The federal tax credit the IRS gave for heat pumps covered improvements made through December 31, 2025.¹¹ If a seller tells you today that “the government pays part of it,” ask them to show you the rule in writing.

Example with real numbers

A family with a 12-year-old air conditioner

An example in words of how the rules apply; prices change with your area.

The equipment

12-year-old central AC; two rooms stay hot

What the DOE says

Over 10 years and rooms too hot: time to think about replacing it

Before deciding

Check the filter, ducts and air leaks

Estimates

Two or more, written and itemized

What you sign

A proposal with cost, models, dates and warranty

The signs come from the DOE;¹ the ducts, leaks and proposal, from ENERGY STAR.³⁴ Plan the cost in your family budget.

Run it with your numbersFamily budget

Public help repairing heating or cooling

The weatherizationweatherizationWeatherization means improvements that make your home more energy efficient, such as sealing doors and windows or making the furnace work better. The U.S. Department of Energy's Weatherization Assistance Program (WAP) makes these improvements in low-income homes to lower their energy costs while protecting their health and safety. States and local organizations run it. Both homeowners and renters can apply; if you rent, the provider gets your landlord's permission before work begins. If you are income eligible, you are placed on a waitlist.See the full definitionClose program, the Weatherization Assistance Program (WAP), is run in each state. According to the DOE, households at or below 200% of the federal poverty guidelines, or that receive SSI, qualify under its rules, and states may use LIHEAP’s limit of 60% of state median income. Homeowners and renters can apply, and if you qualify you are placed on a waitlist.⁹ Many programs repair or replace equipment: Missouri’s, for example, says its typical measures include heating and cooling system repair or replacement.¹⁰

Some LIHEAPLIHEAP (Low Income Home Energy Assistance Program)LIHEAP (the Low Income Home Energy Assistance Program) is a federally funded program that helps with home energy costs, such as heating and cooling. According to the Administration for Children and Families (ACF), it can help with bills, energy crises, preventing shutoffs or reconnecting service, weatherization and minor energy-related repairs. It targets low-income households with a high energy burden or with members who are elderly, disabled or young children. You apply through your local LIHEAP office, and the program does not charge a fee for help.See the full definitionClose offices, the federal energy assistance program, also pay for repairs. In New York City, the HERR benefit helps eligible homeowners repair or replace the furnace, boiler or other heating equipment; it pays the actual cost up to $4,000 for a repair and $8,000 for a replacement, only once every ten years, and the 2026-2027 benefit opened October 1, 2026.⁷ In New Jersey, energy assistance includes emergency heating system services.⁸

Read the weatherization and LIHEAP guides to learn how to apply, and look up your state’s agency in our list of repair-help programs.

If this is you

You live with an older relative and the heat went out

Call your county's energy assistance office and ask about emergency help for the heat.⁸⁷

Your income is low and the equipment is old

Your state's weatherization program may repair or replace it; there is almost always a waitlist.⁹¹⁰

You got only one estimate

Get another one, written and itemized, and compare cost, efficiency and warranty.⁴

Someone feels dizzy near the furnace

Get outside and call 911, as the CPSC recommends.⁶

Costly mistakes

• Mistake: Waiting for the equipment to fail in the middle of summer or winter.

  Instead: Get the yearly check-up: cooling in spring, heating in fall.²

• Mistake: Forgetting the filter for months.

  Instead: Check it monthly and change it at least every 3 months.³

• Mistake: Buying the biggest unit thinking it cools better.

  Instead: Ask for sizing based on your house, insulation and windows.⁴

• Mistake: Replacing the equipment without checking the ducts.

  Instead: Check the ducts and air leaks first.³

• Mistake: Starting work on a handshake.

  Instead: Sign a proposal with cost, models, dates and warranty.⁴

What to do this week

1. Look at the filter: if it’s dirty, change it.³
2. Write down your equipment’s brand, model and age, and when it was last serviced.⁴
3. If your equipment is past the 10 or 15 years the DOE names, get two detailed written estimates.¹⁴
4. Test the carbon monoxide alarms on every level.⁶
5. If your income is low, call your county’s weatherization or energy assistance agency and ask whether there is a waitlistwaiting list (public housing and Section 8)The waiting list is where a public housing agency (PHA) places families who qualify for public housing or a Section 8 voucher when it cannot help them right away. When your name comes up, the PHA contacts you. Because more families need help than there are resources, long waits are common and a PHA may close its list. Each PHA can give preference to certain groups under its written policies. In the voucher program, a PHA may remove you if you do not answer its requests for information, but if that was because of a family member's disability, it must put you back in your place.See the full definitionClose.⁹
6. Add the cost to your family budget and read the contractor scams guide before you sign.