Every one of these comes up on service calls. Nobody who believes them is dumb. They're bits of folklore that sound logical and get passed along because nobody ever had a reason to argue. These are the ones we hear most.
Myth 1: Setting the thermostat lower cools the house faster
An AC has a fixed cooling capacity, rated in BTUs per hour. A bigger gap between the room and the setting doesn't make it work harder. A single-stage compressor runs at the same speed with the thermostat at 75°F or at 65°F, and a variable-speed system ramps up the same way at either setting.
Set it 10 degrees lower than you want and the system just runs past the point where you'd have been comfortable. Then you forget to turn it back up, sit in a 65°F house and wonder why the bill jumped.
Set it where you want to end up, and give it time.
Myth 2: Closing vents in unused rooms saves energy
Less space to cool sounds like less work. Your duct system, though, was designed around a specific airflow, and closing registers raises static pressure. Higher static pressure does four things.
- The blower works harder and uses more energy.
- Less air crosses the evaporator coil, which can freeze it.
- Blower bearings and the motor take extra strain and wear out sooner.
- Every duct joint leaks more, so more cooled air ends up in the attic.
If you really want less cooling in certain rooms, install zone dampers, or look at a multi-stage or variable-speed system with smart vents. Leave the registers open.
Myth 3: Bigger AC is better
An oversized AC moves more BTUs per hour, so it satisfies the thermostat quickly and shuts off. That sounds good. In practice it causes three problems.
- In Houston, pulling humidity out is most of an AC's job. That only happens once the coil is cold and the system runs long enough for water to condense and drain. Short cycles leave the moisture behind.
- Startup is the hardest moment on a compressor and motor. More cycles mean faster wear.
- The house ends up cool and clammy.
Right-sized is best. A proper Manual J load calculation accounts for insulation and glass, orientation, infiltration and occupancy, and it often comes out smaller than a square-foot rule of thumb would suggest.
Myth 4: A working AC does not need a tune-up
"It's cooling, leave it alone." We hear it every spring. A system that cools can still be in trouble. It might be:
- Losing capacity to a slow refrigerant leak
- Drawing more amps than spec because the capacitor is failing
- Starving the coil through a clogged filter
- Leaking cooled air into the attic through bad duct joints
The house still feels cool. Meanwhile the bill creeps up and the equipment wears faster. A thorough tune-up catches all four.
Ours is $99, or $79 with our website coupon. Between the capacity you keep and the problems caught early, it pays for itself.
Myth 5: Filters last 6 months / a year / forever
It depends on the filter.
- 1-inch fiberglass (the cheap blue ones) last 30 days. They start out poor and get worse.
- 1-inch pleated, which most homes use, last about 60 days, less with pets.
- A 4-inch or 5-inch media filter in a whole-home cabinet lasts 6 to 12 months. For most homes, that is the one to have.
- HEPA add-ons follow the manufacturer's schedule.
Set a phone reminder that fits your filter type. In summer, pull it and look once a month. If it's loaded, change it.
Myth 6: One room being too warm or too cold is "just how the house is"
Usually there is a cause you can find.
- The room isn't getting enough air. Look for a closed register upstream, kinked flex duct in the attic or a leaky run.
- The room gains heat the system wasn't sized for, like a south-facing room with three big windows or a converted garage.
- It sits far from the air handler at the end of restrictive ductwork.
A duct test and a balancing pass usually fix it. Sometimes a small zone damper, or a mini-split for the one problem room, is the right call.
Myth 7: A new high-efficiency unit will pay for itself fast
It depends what you compare it to. Going from an old 13 SEER unit to an 18 SEER2 system cuts cooling cost roughly 30 percent. On a $1,500-a-year cooling bill, that's about $450 a year. Much of that saving comes from replacing the old unit at all, though. At 3 tons, the step from our two-stage tier to variable-speed adds roughly $3,500 to $5,600, and the efficiency payback on that step alone runs well past a decade.
Some sales pitches promise "pays for itself in 2 years." It won't. A high-efficiency upgrade earns its money in comfort, with no more swings between cold and warm, and in reliability over a 15+ year service life.
Efficiency is one factor among several. Pick the tier by how long you'll stay in the home, how big your bills are and how much comfort matters to you.
Somebody's uncle is out there right now swearing closed vents save money. Ask us instead, for free. Call 281-992-7866 or book online.