What actually sets the price of a new AC or heating system in Dallas

The house sets the price, not the box

The price of a new air conditioner or heating system in Dallas is set mostly by your house: the size of system the home actually needs, the efficiency and staging you choose, the condition of the ductwork, and the electrical, drainage and code work the installation requires. That is why we do not quote replacements over the phone. Two homes with the same square footage can need different systems, and two quotes for the same home can be far apart because one includes work the other quietly leaves out.

I am Brandon Quigley. My family has run Quigley Heating & Air in Farmers Branch since 1945, and across three generations we have watched homeowners compare a low number with a complete one without realizing they were looking at two different jobs. This guide walks through each cost driver so you can read any estimate, ours included, and know what you are paying for.

Size: why a bigger unit is not a better deal

The first driver is capacity. A larger system costs more to buy, and many people assume extra capacity is free insurance against a brutal August. It is not. ENERGY STAR's guidance for hiring a contractor puts it plainly: a bigger system isn't always better, and equipment should be sized from the house itself, including its size, insulation and windows. In our experience, oversized equipment turns on and off too often, which means less comfort and more wear on the parts that start the system.

An oversized air conditioner cools the air quickly and shuts off before it has pulled enough moisture out, so the house feels clammy at the right temperature. An undersized one runs nonstop on the hottest afternoons and still loses ground. Many older systems were sized by rule of thumb, and if the attic has been reinsulated or the windows replaced since then, the right size may have changed. Our comfort consultant evaluates the home rather than copying the number off the old nameplate, and the correct size is usually the cheapest one to own over its life.

Here is what a real sizing visit looks like. Someone walks the house, asks which rooms run hot and when, notes which way the large windows face, looks at the attic insulation and follows the duct layout. If a contractor writes a quote after glancing at the old outdoor unit, the size on that quote is simply the old size, whether or not it was ever right for the house.

Efficiency and staging: paying now or paying every month

The second driver is how efficient the equipment is and how it runs. A single-stage system is either fully on or fully off. A variable-speed system adjusts its output, running longer at lower speed. Our top recommendation for replacements is Lennox or Trane high-efficiency variable-speed equipment, because it holds steadier temperatures, controls humidity better and uses less electricity than older units. It also costs more on installation day.

Whether that premium pays you back depends on how long you plan to stay in the house, how hard your system works and what your bills look like now. ENERGY STAR says that if your heat pump or air conditioner is more than 10 years old, certified equipment can cut heating and cooling costs by as much as 20 percent. Efficiency ratings help you compare: on SEER2, the current cooling efficiency rating, a higher number means a more efficient system. That is why our estimates come in tiers. You can see what each step up in efficiency costs and decide where the value is for your house, instead of taking our word for it.

Ductwork is where quotes quietly split apart

The third driver is the duct system, and it is the one most often left off a low quote. ENERGY STAR estimates that about 20 to 30 percent of the air that moves through a typical duct system is lost to leaks, holes and poorly connected ducts. In most homes around here those ducts run through a hot attic. Connecting a new high-efficiency system to leaking, crushed or undersized ducts means paying for efficiency you will never receive.

When we look at a replacement, we look at the ducts: whether they are sealed, whether the returns are large enough to feed the new system, and whether sections need repair or replacement. If ductwork has to be extended or rebuilt, the installation takes longer and costs more, and the estimate should say so in writing. If one quote includes duct work and another does not, you are not comparing prices yet.

Ask about the return side as well. Many homes have one small return grille trying to feed a system that needs far more air coming back to it. The result is a noisy system, a starved coil and rooms that never quite catch up. Adding or enlarging a return is not glamorous work, but it is often the difference between a new system that performs as rated and one that only looks new.

The parts of the job nobody photographs

The fourth driver is everything around the equipment. These items rarely appear in advertising, but they decide whether the system runs safely and lasts. Ask every contractor which of them are included, because each one is a place where a low price can come from skipping work.

The drain matters more than people expect. In many homes the indoor coil sits in an attic above a finished ceiling, and a clogged drain without a working float switch is how a cooling problem becomes a drywall problem. Electrical work matters for the same reason: new equipment connected to a breaker or wire that no longer matches it is a safety issue, not a detail.

• Electrical: the outdoor disconnect, breaker and wiring sized for the new equipment
• Condensate drain line, drain pan and safety float switch for the indoor coil
• Refrigerant lines evaluated, and reused or replaced as the new equipment requires
• Thermostat compatibility, especially with variable-speed equipment
• Permits and inspections where your city requires them
• Removal and disposal of the old equipment
• Access work in tight attics or closets

Replacing heating and cooling together, or one at a time

The fifth driver is scope. Replacing the heating and cooling systems together is generally more cost-effective than doing them in two separate projects, because the labor, the matched components and the setup happen once. The indoor coil and the outdoor unit also have to be matched to perform as rated, so swapping only the outdoor unit on an older system is rarely the bargain it looks like.

That does not mean you always replace everything. If your furnace is much younger than your air conditioner and in good shape, replacing the cooling side and the coil may be the right call. ENERGY STAR suggests having a furnace evaluated once it is more than 15 years old. The type of heat matters too: a gas furnace, a heat pump and a dual-fuel system that uses both are priced differently, and I explain the tradeoffs in my guide on choosing a heat pump or gas furnace.

Timing, financing and what the system costs after installation day

The sixth driver is timing. Early spring and fall are the easiest seasons to schedule a replacement with little wait, and you have time to compare options carefully. A replacement forced by a breakdown in July still gets done, but you are making a large decision in a hot house. If your system is aging, planning the replacement before it fails is the cheapest kind of urgency.

For many families the real question is the monthly cost. We offer Wells Fargo financing with approved credit, with monthly payments and online account management, and our office can explain the current promotions. Then there is the cost of keeping the system healthy. Our Q Club maintenance plan starts at 17 dollars a month for the first system, includes two tune-ups a year and builds loyalty credits toward future equipment. I cover what a plan should include in my guide to whether a maintenance plan is worth it.

Reading two estimates side by side

ENERGY STAR recommends getting written, itemized estimates and a signed proposal that lists the costs, model numbers, job schedule and warranty information. That is good advice, and it also gives you a way to compare quotes fairly. Lay them next to each other and check each line below. Where one estimate is silent, ask. A missing line is either included and unstated, or not included at all, and you want to know which before you sign.

• Model numbers for the outdoor unit, indoor coil and furnace or air handler
• Efficiency rating and whether the equipment is single-stage, two-stage or variable-speed
• How the size was chosen, and whether anyone measured the house
• Duct sealing, repair or replacement, spelled out
• Electrical, drain, thermostat and permit work
• Parts and labor warranty terms, and who honors them
• Installation schedule and financing terms

What our estimate visit includes

When you ask us about a replacement, a comfort consultant comes to the house, asks which rooms bother you and when, looks at the existing equipment and the ducts, and evaluates the home. You get a tiered written estimate with clear options, from a solid standard system to Lennox or Trane high-efficiency variable-speed equipment, along with the financing details. You decide on your own timeline. If the system is younger and a repair makes more sense, we will tell you that instead; my guide on an AC that runs but does not cool explains how we make that call.

If you go ahead, a new system is typically in service in under a day, longer when ductwork has to be extended. I walk through that day in what happens when the AC is replaced. We serve Dallas, Farmers Branch, Carrollton, Coppell, Frisco, Garland, Highland Park, Plano, Richardson and University Park, and our Texas license number is TACLA23686E.

Questions people ask me