When old air conditioners have to be replaced the question is what to replace – the entire air conditioning system or the failed parts only. The answer is the entire air conditioner needs to be replaced.

There are two main parts in an air conditioner – the evaporator and the condenser. You’ve never seen the evaporator. It quietly sits inside the ductwork and absorbs heat from inside air into the refrigerant. The condenser, the other main part, sits outside of the house and looks like it’s doing all the work. Actually, it’s only doing half the job. The condenser squeezes heat out of the refrigerant into the outside air. Most of the time the culprit is the condenser since this is where all the wear and tear happens. You might be tempted to replace the condenser only.

Condensers and evaporators are not good at all at adjusting to each other. If the evaporator absorbs too much heat from the house, the condenser will overheat. If the evaporator doesn’t absorb enough heat, it will freeze itself. The only

way make sure an air conditioner will work properly is to match its two main components – the evaporator and the condenser.

It’s fairly easy to match components when you install a new air conditioner, as you can see at
ARI Reference Number page. However, it’s much more difficult to match the components of aging systems. Virtually all the systems that may require condenser replacement today were designed to work in 6, 8, or 10 SEER air conditioners. All the air conditioners that are on the market today are 13 SEER and up. Good luck matching 10 SEER (or even 8 or 6 SEER) evaporator with 13 SEER condenser.

This is why; if you have to replace your old air conditioner, replace everything.


EPA stands for Environmental Protection Agency
It is an agency which was created for the purpose of protecting human health and the environment by writing and enforcing regulations to protect the environment and human health


The AHRI reference number for an air conditioner guarantees it to have Energy Star efficiency, the proper SEER rating, and the right amount cooling. Every new air conditioning unit sold must have the AHRI reference number.

What is AHRI reference number?

A residential central air conditioner has two main parts: the condensing unit installed outside of the house and the evaporator installed inside the ductwork. For an air conditioner to work up to specs or even to work at all, these two components must be properly matched.

Each condenser works properly with only a limited number of evaporator models. Each of the matches has a unique identifier — the AHRI reference number.

Another must have a component of the air conditioning system is air flow. Airflow is provided by the furnace (fan coil, air handler). For most of 14 SEER units and for virtually all higher SEER air conditioners and heat pumps, manufacturers also prescribe the particular furnace (air handler) models to be used. If this is the case, the furnace model is also included in AHRI number.

It brings the total number of must have components to three:

  1. Condensing Unit
  2. Evaporator (coil, blower coil)
  3. Furnace (fan coil, blower coil, air handler)

How To Check AHRI Reference Number?

On the invoice, among other information, you contractor must show three crucial pieces of data –

the model number for the condenser, the model number for the evaporator, and the AHRI reference number.

Before the evaporator gets concealed inside the ductwork for good, check that the model number on the evaporator matches the number on the invoice. Do the same for the condenser.

Go to HRAI Directory. Enter the AHRI reference number from the invoice as shown below. Click “Search”. The site will give you the model numbers for the condenser and for the evaporator, as well as the SEER rating for the air conditioner and its cooling capacity (See the picture at the bottom). The numbers must match the numbers on the invoice. (Symbol * stands for any digit or letter)

As we can see in the picture, this particular AHRI number 3598225 describes a system that also includes the furnace.
About AHRI. It stands for Air-Conditioning and Refrigeration Institute. AHRI is an internationally recognized leader in developing standards for HVAC products, as well as certifying their performance.

AHRI number


AHRI Reference Number
♦ AHRI Air conditioners and heat pumps
Replacing Air Conditioner
Cost of Air Conditioning



AFUE stands for Annual Fuel Usage Efficiency. The AFUE shows how efficiently a furnace transfers heat from the energy created by burning the gas to the house. The higher the AFUE rating the more energy-efficient the furnace. The mandatory minimum AFUE rating in Canada is 90 percent.

The top of the line Signature (SLP98) furnaces have 98% efficiency! Most of the Elite (EL) furnaces have 96% efficiency.


SEER rating tells how much heat (BTU) can an air conditioner remove out of the house per watt of electricity it uses. Higher SEER rating equals higher efficiency of the air conditioner.

SEER ratings help when comparing two or more air conditioners. The higher SEER the more efficient the air conditioner. The spreadsheet below shows cost of air conditioning with different SEER rating.

The cost of electricity is assumed 6 c/kW. The amount of heat produced by different physical objects is in BTU/hr. All the numbers are approximate.

A human body:
-Resting – 350
-Hard Working – 2,000

A regular 100 W bulb – 340

A kitchen stove:
– A small burner – 5,000
– A Large burner – 20,000
– An oven – 20,000

A computer – 1000

Example 1

The size of your air conditioner is 1 ton. How much does it cost you to run your air conditioner for 1 hour?
One ton of cooling is 12,000 BTU/h. After we enter 12000 into the spreadsheet, it returns us the cost 9 cents an hour for an old 8 SEER air conditioner and 5.14 cent for a Energy Star 14 SEER air conditioner.

Example 2

A 3 ton air conditioner runs on average half of the time around the clock. How much electricity does it use?
Since one ton of cooling removes 12,000 BTU/h of heat, we enter 12,000×3=36,000 into the spreadsheet. It returns 27 cents an hour for the old air conditioner, 13.5 for the new and 15.43 for a mainstream 14 SEER unit. With this numbers the old unit costs $0.27x24x0.5=$3.24 a day to run. The 16 SEER unit costs $1.62 and the 14 SEER unit costs $1.85 a day to run.

Example 3

You are planning a party for 10 people. The party will last 4 hours with some activities, like dancing – 800 BTU/h per person. Total 800 x 10 x 4 = 32,000 BTU One hour of cooking will precede the party. Oven and 2 large burners will produce 20,000 x 3 = 60,000 BTU. All the extra heat in the house will total 92,000 BTU.

Cost of cooling is 69 cents with an old air conditioner and 39.4 cents with 14 SEER new one. Perhaps you can afford cooling of your party if you can afford the party itself.

One more consideration though.

While cooking you will need 60,000 BTU/h EXTRA cooling capacity, and this is 5 ton of cooling – the size of the biggest residential unit on the market. You do not have that much EXTRA cooling available. The most effective way to fight cooking heat and moisture would be using of the kitchen exhaust fan.

Extra heat from 10 people will require less than 1 ton of cooling . Most probably your air conditioner will be able to handle it if it’s not too busy fighting sun load.

Now you are ready to play with numbers yourself.

ARI Reference Number
Replacing Air Conditioner
Cost of Air Conditioning