How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

Should I repair or replace my old air conditioner?

Saturday, October 6, 2018

   Generally, from an accountant’s total-cost standpoint and allowing for the time-value of the delayed expenditure for a new system, it’s less expensive to nurse your existing a/c unit until it dies. But one other factor may tip the scales toward earlier replacement: already-inefficient air conditioning systems get even less efficient as they get older, especially after about 20-years. The compressor draws more amps as it ages, and the temperature split (difference between the ambient room air and the cold air coming out the ducts) tends to decrease too. Your a/c service tech can give you a rough evaluation of the system’s current efficiency as a guide when you’re trying to decide whether to repair or replace. 

   Although the SEER rating is not marked on older units, the average SEER for a system manufactured from 1970 to 1996 was between 9 and 10, trending up gradually towards 12 between 1997 and 2006. If your current SEER is 9 or below, then a new system will be at least 40% more efficient. So replacing an HVAC system that is 20-years old or more will make a significant dent in your monthly electric bill.

   When it is time for replacement, systems with SEER ratings up to 20 and beyond, like the one shown above, are available. Each notch of efficiency means more initial outlay and, for the very high SEER systems, more maintenance because of the more complex components. For most situations, the minimum or near-minimum SEER is the most cost-effective choice; but the length of the cooling season and cost of electricity in the region can change the equation. At the southern tip of Florida in Key West, for example, where the cooling season is longer and the cost of electricity is higher than normal, a high-SEER system makes both environmental and budget sense. 

    Also see our blog post What is the SEER of my old air conditioner?


  To learn more about heating and air conditioning systems, see these other blog posts:

How can I find out the SEER of my air conditioner? 

My air conditioner won't turn on. What's wrong? 

How can I find out the size of my air conditioner? 

How can I find out the age of my air conditioner or furnace?

How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

Where is the air filter for my central air conditioner and furnace? I can’t find it? 

Does an old air conditioner use more electricity as it ages? 

How did homes stay cool in Florida before air conditioning?

How can I find out the size of my air conditioner? 

How can I find out the age of my air conditioner or furnace? 

•  What is wrong with an air conditioner when the air flow out of the vents is low?

Why has the thermostat screen gone blank? 

Why does it take so long to cool a house when an air conditioner has been off for a while? 

Why is my air conditioner not cooling enough? 

What are the most common problems with wall/window air conditioners?  

Will closing doors reduce my heating and cooling costs? 

    Visit our  HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests



When It First

Became Code

"Should I Buy A..."

Park Model Homes


Shingle Roofs




Wind Mitigation

Roof and Attic

"Does A Home


Pool and Spa

"What Is The Difference Between..."




Concrete and

Concrete Block

Metal Roofs


Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants


Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil





Exterior Walls

& Structures


Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers



Doors and Windows



Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps


Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.






Air Conditioner & Furnace Age/Size


Electrical Switches





Water Intrusion

Electrical - Old

and Obsolete


Foundation Certifications

Tiny Houses

About McGarry and Madsen



Buying a home in North/Central Florida? Check our price for a  team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.

Moisture Problems

Crawl Spaces