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Texas homes paid 14.94 cents per kilowatthour in 2024. That's the number your new system has to work against every time it cycles on. A unit sized right for your house and running at a high SEER2 rating pulls less power to do the same job, and in San Marcos that difference shows up on the bill month after month. An old or oversized system wastes power regardless of the rate, but at Texas prices that waste costs more than it would somewhere cheaper. When you're comparing installation quotes, the efficiency rating on the unit matters as much as the price tag on the job.
NOAA nClimDiv, 1991–2020 normals
A bigger air conditioner isn't a safer bet, it's a worse fit.
Oversized units cool the air fast and shut off before they pull the moisture out, so the house feels clammy even at the right temperature.
Hays County is zone 2A, a hot and humid climate where cooling carries most of the year's load. That's why the minimum efficiency here is higher than what the rest of the country requires. Split-system central air conditioners installed in the Southeast have to hit at least 14.3 SEER2 below 45,000 Btu/h, compared to the national manufacturing floor of 13.4. If a contractor quotes you something at the lower number, it isn't legal to install here. A federal tax credit is also available for qualifying high-efficiency equipment, on top of meeting the regional minimum.
Hays County saw 108 severe weather events between 2015 and 2024, including hail and damaging wind. Statewide, a third of households lost power for a day or more in 2024. Your outdoor unit sits through all of it, so where it goes and what shields it matters. Worth deciding before install day, not after a storm.
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Seven months of cooling here, April through October. June, July and August push the afternoon high to 94 degrees on average, so the system runs long hours against real heat, not mild days. A unit sized right for your house will cycle on and off at a steady pace through all of that. One sized wrong runs long and still falls behind, or shuts off before it pulls the moisture out. Either way the strain lands on the compressor first, and it shows up sooner here than in a place that only asks this of a system for a few months a year.
A straight swap means the old condenser and coil leave before the new ones go in. The refrigerant gets recovered first, it can't legally be vented to the air. If the line set or pad is being reused, it gets checked before the new unit sits on it. Anything cracked or undersized gets replaced rather than reused, since the new system depends on it too.
Older systems run on a refrigerant that's being phased out, and newer units don't use it. That means the old line set, coil and condenser usually can't mix with new equipment even if the metal looks fine. Expect the whole matched set to go, not just the loudest or oldest-looking piece of it.
Estimates for a typical Hays County home, from EIA household energy data, Texas fuel prices and NOAA climate normals. Your home will differ.
The crew shows up with a load calculation already done, not a tape measure and a guess. That number decides the tonnage, so the sizing argument is settled before anyone touches the old unit. Expect the indoor coil and outdoor condenser swapped as a pair, the line set checked or replaced, and the new unit set on a pad that's actually level, since a tilted pad strains the compressor from day one. The ductwork gets a look too. A new system moves a specific amount of air, and supply runs that are crushed, leaky or undersized choke that airflow no matter how good the condenser is. Startup means the refrigerant charge gets weighed in and verified, not eyeballed, then the system runs through a full cycle while static pressure and temperature split get checked. A good install ends with someone walking the thermostat settings with you, not just the invoice.
