There's no reliable square-footage rule for AC sizing, and any contractor quoting your tonnage over the phone based on square feet alone is guessing. The only accurate way to size a system is a Manual J load calculation, which factors in insulation, window count and orientation, ceiling height, duct condition, and how much heat your specific house gains on a 100 degree Texas afternoon. Two houses with identical square footage can need genuinely different tonnage depending on those details.

Why 'One Ton Per 500 Square Feet' Gets It Wrong

That old rule of thumb almost always oversizes a home, and it can be wrong by a wide enough margin that it matters. A well-insulated, well-shaded modern home often needs closer to one ton per 1,000 to 1,400 square feet, not 500. A contractor sizing purely off square footage on a larger newer-construction DFW home can end up recommending a system nearly twice as big as what the house actually needs.

An oversized system sounds like a safe bet, more capacity can't hurt, right, but it's the opposite. A system that's too big cools the air fast and shuts off before it's run long enough to pull humidity out of the house. That's exactly why some DFW homes feel cold and still clammy at the same time. The unit also short-cycles, turning on and off more frequently than it should, which wears out the compressor faster and drives up your electric bill despite the "bigger" system.

When a contractor's quote gets to a tonnage number without asking about your insulation, your windows, or walking your attic, that's worth questioning. A correctly sized system, done right, typically saves meaningfully on the annual energy bill compared to a rule-of-thumb oversized one, and it also runs longer humidity-removing cycles, which is a bigger deal in DFW than in drier climates since humidity is what actually makes a house feel hot even at a "comfortable" thermostat setting.

Metroplex Air & Heat runs a full Manual J load calculation on every system replacement quote in Frisco, Plano, McKinney, Prosper, and Allen rather than sizing off square footage, since getting the tonnage right the first time is what actually keeps a house comfortable and the bill reasonable.

Square footage rules of thumb miss the right AC size roughly 70% of the time. A Manual J load calculation is the only way to size it correctly.

Clear technician walk-throughs

Load calculations, not guesses

Straight answers

Respect for your home

Documented work

Practical next steps

A straight AC replacement, meaning the same type of system in the same location, usually takes 4 to 8 hours and gets finished in one day. What throws people off is the total timeline: once you count getting a quote, ordering equipment, pulling a permit, and finding an open install slot, most DFW homeowners are looking at 1 to 3 weeks from first phone call to cool air blowing again, longer during peak summer.

A two-person crew can usually complete a like-for-like swap in a single visit. The work isn't complicated, it's just methodical: recover the old refrigerant, disconnect and remove the outdoor condenser and indoor coil, set the new equipment, run new line sets if the old ones are corroded or the wrong size, wire it in, pull a vacuum on the lines to remove air and moisture, charge the system with refrigerant, then test airflow, temperature split, and thermostat function before they leave.

What Turns a One-Day Job Into Two or Three

The timeline stretches when the job is more than a parts swap. Switching from a downflow to a horizontal furnace configuration, moving equipment to a new spot in the attic or garage, adding a return air duct, or upgrading an electrical panel to handle a higher-amperage heat pump all add hours or a second day. Older homes in McKinney and Plano with narrow attic hatches or steep roof pitches also slow things down simply because of access, not because the equipment itself is harder to install. Full duct replacement is the one that really stretches a timeline, sometimes into 2 to 3 days, but that's a separate project from the equipment swap itself.

The Real Bottleneck Is the Calendar, Not the Labor

In June, July, and August, DFW HVAC companies are running near capacity. A quote can usually happen within a day or two of your call, but the install date itself often lands one to three weeks out once equipment has to be pulled from a warehouse and a crew has an open slot. This is the part that catches people off guard when their system dies in the middle of a 100 degree stretch and they assume same-day replacement is normal. It can happen, but it's the exception, not the rule, during peak season.

Metroplex Air & Heat quotes most straight replacements within 24 to 48 hours of the initial visit and keeps a stock of the most common residential tonnages on hand specifically to avoid the multi-week wait that hits a lot of homeowners in July and August.

A same-size AC swap takes 4 to 8 hours on install day, but the full process from quote to cool air usually runs 1 to 3 weeks in North Texas.

Any new AC or heat pump installed in Texas has to meet a minimum of SEER2 14.3, which is roughly equivalent to the old SEER 15 rating before the testing standard changed. That's the legal floor, not the recommended number. For a house running its air conditioner from April through October like most homes in Frisco, Plano, and McKinney do, something in the 15.2 to 17 SEER2 range usually pays for itself faster than the bare minimum unit does.

If you're comparing a quote against a number you remember from a few years ago, know that the testing method changed and SEER2 numbers run about 5 percent lower than old SEER for the same physical equipment. A unit rated SEER2 14.3 isn't a downgrade from an old SEER 15 system, it's the same performance measured a stricter way. This trips up a lot of homeowners who think a "15 SEER2" system is worse than the "16 SEER" unit they had before. It's roughly a wash.

Why the Minimum Isn't Always the Right Call in DFW

Efficiency ratings matter more in climates where the system runs constantly, and North Texas is exactly that climate. A house here can rack up 2,000+ cooling hours a year between the humidity and the summer heat. Every point of SEER2 you add above the minimum shaves a real percentage off your summer electric bill, and that percentage compounds every single year you own the system, typically 12 to 18 years. In a mild climate that only runs AC three months a year, chasing a high SEER2 number rarely pays back. In DFW, it usually does within a reasonable number of seasons.

A high SEER2 number on paper doesn't guarantee comfort if the system is sized wrong or the ductwork is undersized. A correctly sized 15 SEER2 system that's actually matched to your home's load will outperform an oversized, mismatched 17 SEER2 unit every time. SEER2 is a factor in the decision, not the whole decision. Ask any contractor quoting you a high number what the total installed cost difference actually looks like against the payback period, in real dollars, not just percentages.

Metroplex Air & Heat walks every DFW homeowner through the SEER2 tiers against their actual electric bill and square footage before recommending a number, since the "right" rating depends more on how the house holds heat and how long you plan to own it than on any one-size-fits-all rule.

Texas requires a minimum SEER2 14.3 rating, but for DFW's long, hot summers, 15.2 to 17 SEER2 is usually the smarter buy. Here's how to decide.

The clearest signs it's time to replace instead of repair: your system is 12 to 15 years or older, it still runs on R-22 refrigerant, the repair quote comes in at half or more of what a new system costs, or it's needed three or more repairs in the past two years. Any one of these on its own is worth a hard look. Two or more together usually means replacement is the better financial call.

Most residential AC systems are built for a 12 to 15 year service life, and Texas heat shortens that window compared to milder climates because the equipment runs harder for more months of the year. A 15-year-old system limping through another DFW summer is running on borrowed time even if it's technically still cooling the house. Parts availability drops off for older equipment too, which means repairs on an aging system take longer to source and cost more per visit than they did five years earlier.

If your system was installed before roughly 2010, there's a good chance it runs on R-22 refrigerant, which the U.S. stopped allowing new production of back in 2020. Whatever R-22 is still floating around the supply chain costs several times more per pound than the R-410A used in current systems, and that price keeps climbing as the remaining stock shrinks. A refrigerant leak on an R-22 system can turn a routine repair into an expensive one fast, and it's one of the clearest signals that the smarter move is replacing the whole system rather than topping off a dying one.

A repair quote that lands at 50 percent or more of the cost of a full new system installed isn't a repair, it's a down payment on a system you're going to need anyway within a year or two. Some contractors also use a rule of thumb where you multiply the unit's age by the repair cost: if that number tops $5,000, replacement usually wins on the math even if the repair itself sounds cheap in isolation.

None of this means every older system should be replaced on sight. A capacitor, a contactor, or a low refrigerant charge on a system that's otherwise under 10 years old is usually a straightforward, inexpensive fix and replacing the whole unit over it would be wasteful. The decision should come down to the specific repair cost against the system's age and history, not a blanket rule that older automatically means replace.

Metroplex Air & Heat gives a straight answer on repair versus replace on every service call, including the actual numbers behind the recommendation, not just a sales pitch for a new system.

If your AC is 12+ years old, needs R-22, or a repair quote tops half the cost of a new system, replacement usually beats another repair. Here's how to tell.

For most of a North Texas winter, a heat pump is the more efficient choice, delivering three to four units of heat for every unit of electricity it uses. A gas furnace pulls ahead when temperatures drop into the 20s and below, producing strong, fast heat exactly when a hard freeze hits. Because DFW gets both mild stretches and sudden cold snaps in the same winter, a lot of homeowners here end up choosing based on which trade-off matters more to them, or opting for a dual-fuel system that uses both.

DFW winters spend most of their time in the 40 to 60 degree range, and that's the sweet spot where a heat pump operates at its most efficient. If you're not on natural gas already, a heat pump also avoids the cost of running a new gas line, which can add several thousand dollars to a furnace install in a home that doesn't already have gas service. Heat pumps also double as your AC in the summer since the same outdoor unit runs in reverse, which simplifies the whole system down to one piece of equipment instead of two.

When a cold front drops temperatures into the 20s or lower, which happens most North Texas winters at least a handful of times, a gas furnace produces heat faster and holds it more consistently than a heat pump working near the bottom of its efficiency range. If your priority is fast recovery after the front door's been open, or you've been burned by a heat pump struggling to keep up during a February freeze, a furnace solves that directly.

The Dual-Fuel Option Most DFW Homeowners Don't Know About

A dual-fuel system pairs a heat pump with a gas furnace and switches between them automatically based on outdoor temperature. The heat pump handles the mild months efficiently, and the system kicks over to gas only when temperatures drop low enough that gas becomes the better performer. It costs more upfront than either system alone, but for a North Texas winter that swings between 60 degree days and sudden freezes in the same week, it removes the trade-off entirely instead of asking you to pick a side.

Don't decide this based on efficiency alone. Factor in whether your home already has a gas line, how long you plan to stay in the house, and how much a rare hard freeze week actually bothers you versus how much you care about a lower electric bill the other five months. There's no universally correct answer here, only the one that fits your specific home and how you use it.

Metroplex Air & Heat installs all three configurations across Frisco, Plano, McKinney, Prosper, and Allen and can run the actual cost comparison against your current gas and electric rates before you commit to one.

Heat pumps handle about 90% of a typical DFW winter more efficiently than gas, but hard freezes favor furnaces. Here's how to pick, including dual fuel.

The biggest red flag in choosing an HVAC contractor is a quote that comes in thousands of dollars below every other bid you got. That gap has to come from somewhere, and it's usually unlicensed labor, no permit, cut-rate equipment, or a plan to pad the bill later with "surprise" issues once the job has started. Beyond price, watch for missing licensing, vague written estimates, no mention of a permit, and pressure to sign the same day.

Why the Lowest Bid Is Often the Most Expensive One

A legitimate HVAC company quoting thousands less than everyone else is doing it by cutting something you can't see at the time of the quote: skipping the permit, using a smaller or lower-quality line set, sending a single unlicensed installer instead of a trained crew, or planning to hit you with change orders once your old system is already torn out and you're not in a position to say no. Comparing three quotes side by side is the easiest way to spot an outlier before it becomes your problem.

Texas requires HVAC contractors to hold a state license through the Texas Department of Licensing and Regulation, and a legitimate company will give you that license number without hesitation. Ask about liability insurance and workers' comp too. If a worker gets hurt on your property and the contractor isn't properly insured, that liability can land on you as the homeowner, not the company that sent an uninsured crew to your house.

Every North Texas city requires a mechanical permit for a full HVAC replacement, and that permit triggers an inspection that verifies the work meets code. A contractor who doesn't mention a permit on the quote is either planning to skip it, which is illegal and can void your equipment warranty, or planning to charge you for it separately after you've already committed. Either way, ask directly and get the answer in writing before you sign anything.

A Legitimate Quote Takes Time to Put Together

A contractor who quotes a full system replacement over the phone without seeing your attic, your ductwork, or your electrical panel is guessing, and that guess tends to turn into change orders once the crew shows up and finds something the phone quote didn't account for. An in-person visit before a firm number is a basic sign of a contractor doing this the right way.

Metroplex Air & Heat provides its TDLR license number and proof of insurance on every quote request, and every full system quote includes an in-person visit and the permit cost spelled out in writing before any work is scheduled.

A quote thousands below competitors, no permit mentioned, or high-pressure tactics are the top HVAC contractor red flags. Here's what to check before signing.

What Size AC Unit Do I Need for My House?

Why 'One Ton Per 500 Square Feet' Gets It Wrong

Why Oversizing Actually Hurts You

What a Manual J Actually Looks At

What This Means for Your Quote