HVAC Systems

Everything You Need to Know about Central Heating & Air Conditioning Systems


Furnaces which blow heated air through a duct system are referred to as “forced-air” heating. Natural gas and electricity are the most common furnace fuels in DFW.

AFUE = Annual Fuel Utilization Efficiency. This number tells you how much of the heat produced is usable (versus vented out with the exhaust). An 80% AFUE means 20% of the heat is lost during venting. Today’s furnaces can be as high as 97%. The minimum AFUE rating for a new gas furnace is 80%.

At a glance, it seems you should want the highest AFUE rated furnace available. Due to mild DFW winters, however, the difference in purchase price might be more than the fuel savings during the furnace’s lifetime.

A better investment may be to invest the high-E furnace cost-difference into attic insulation plus a Foil Radiant Heat-Barrier, if you already don’t already have these energy-saving features. The cost of these two energy-savings upgrades may be less than the cost of upgrading to a 97% AFUE furnace AND these upgrades will create a huge reduction in cooling costs too.

Heat Pumps

NOTE: When you buy a heat pump, you are also getting a new Air Conditioner.

A Heat Pump is an air conditioner with the capability to run in reverse. When in reverse, heat is added to your home versus removed. The system switches over to the furnace when temps get too low to efficiently extract heat from the outside air, at roughly 40 degrees.

The diagram to the right shows a heat pump in heating mode.

If you already have natural gas in your home, your Purchase Cost + Operating-Costs are minimized with an 80% gas furnace + central air conditioner.

IF you have an all-electric home (no gas service) — the initial cost to convert to a gas furnace is notably higher due these requirements:

  1. Installing a gas line from the street / alley to the home PLUS
  2. A gas line to the furnace (from the new gas line from the street).

For an all-electric home, It’s less expensive to install a new electric furnace and heat pump, as heating-costs for this combination are similar to a gas furnace. The additional charge for the heat pump will be offset by much lower electric heating charges. The chart above shows the cost of operating an electric furnace is 2-1/2 times that of a heat pump.

Central Air Conditioners

A central air conditioner is what cools most DFW’s homes. The big difference among central a/c units is their energy efficiency and purchase price (which are related).

SEER = Seasonal Energy Efficiency Ratio. This is your guide as to how efficient a central a/c unit is.

Today’s high-efficiency a/c’s have a SEER up to 25. The cost to operate a SEER 14 A/C is 2-1/3 less than a SEER 6. The cost to operate a SEER 25 is less than 1/4 of a SEER 6. It becomes obvious that replacing an old a/c with a SEER 13 in DFW will pay for itself in energy savings over the life of the unit — especially when considering the remaining lifespan of the old a/c, which will have to be replaced sometime in the near future.

Is there is a “best option” of initial purchase cost + operating costs over the lifetime of the unit?

Will a higher SEER produce additional savings over its lifetime? To compute lifetime operating costs (Purchase Cost + Energy Costs) for different SEER’s, use this calculator below.

Ask your HVAC installer to provide their installed price for a 14 SEER, a Mid-Range SEER, and the Highest SEER. You can then enter each cost into the calculator.
TXU’s average price per Kilo-Watt Hour (KwH) = 7.5 cents. You can also look at your electric bill to know specifically what you are paying per KwH.

Using the calculator, you can determine the lifetime cost for each SEER. The calculator automatically enters the average lifespan of each.

Energy & Cost Savings Calculators U.S. Dept. of Energy


Even in DFW, the least expensive option may be a lower SEER rated central air conditioner when considering the purchase cost difference.

Here are a couple of other things to consider:

  • Will you live in the home for the entire lifespan of the a/c (assume 10-15 years)?
  • Will a higher efficiency a/c be a selling feature when selling the home. Yes, of course. However, buyers are not always willing to pay for a home’s amenities. Their decision will be based on the amenity and the price of the home. A high SEER air conditioner will have more impact on a large home than a smaller one.

Also, if it comes down to a Hi-E air conditioner or something which has a high visual appeal (such as granite counters) most buyers will have more interest in what they see.

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If you need a/c or heating repair or a new system installation in the Dallas metro area, give us a call at 972-225-5257 or contact us online.
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