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Electricity in Texas ran 14.94 cents per kilowatt-hour in 2024. A mini split works against that price every time it cycles on, so the efficiency of the unit matters more here than somewhere power costs less. These systems condition the air directly, with no ductwork losing heat or cool air along the way. That alone cuts into the waste a central system can have. The size of the unit and how well it matches the room still decide most of what you pay to run it, so that match is worth getting right at installation rather than fixing later.
NOAA nClimDiv, 1991–2020 normals
Rockwall County runs its cooling six months a year, May through October.
A mini split here earns its keep most of the year, so sizing it right from the start matters.
April is the month to get a mini split installed here, before cooling starts in May. Pick a contractor, work out the sizing, and get it on the wall while there's no rush. Wait and you're making the same decisions on a hot day with a house that's already behind. Whatever goes in during April is what you're living with from May through October, so it's worth getting right before you need it running.
Rockwall is zone 3A, and any mini split going in has to clear 14.3 SEER2 for cooling and 7.5 HSPF2 for heating, the same minimum as any split-system heat pump. That floor is what keeps a unit from running up your bill in a place where summer is long and power isn't cheap. A federal tax credit is available on qualifying systems, worth checking into before you settle on a model.
Find a contractorSix months of cooling, and the hottest stretch averages 93°F in the afternoon. That's what the unit sits under, day after day, from May through October. A mini split sized right for the room handles that load without strain. One sized off a guess runs longer than it should, or short-cycles trying to keep up, and either way the compressor takes the wear for it. Get the sizing right at installation and the unit spends those six months doing its job instead of fighting the room.
A contractor works out sizing from a load calculation, weighing window area and direction, ceiling height, insulation, and what's on the other side of each wall. Square footage alone leaves out too much. Rooms that measure the same can need different capacity depending on how much sun hits the glass and what sits above or below them.
A unit too big for the room cools the air fast and shuts off before it pulls the moisture out, so the room ends up cold and damp at once. It also cycles on and off more, and that start-stop wears the compressor harder than running steady. Bigger isn't a safety margin here. It's the thing that causes the problem.
Installation cost comes down to how much hardware goes in and how hard it is to get it there. A single zone with one indoor head and one outdoor unit costs less than a multi-zone system running several heads off one condenser. Line set length and routing matter too. A straight run through an exterior wall to a condenser sitting right outside costs less than a run that has to travel through framing, around corners, or up to a second floor. Electrical work adds to it if the circuit the system needs doesn't already exist, since that means running new wire back to the panel. Where the outdoor unit lands matters as well. A spot that's easy to service costs less than one that needs a special mount or extra pad work to sit level and drain properly.
The old system doesn't need to come out before the new one goes in, but most installs end that way since the indoor head usually takes the same wall space. If it's a central system being replaced, the air handler and ductwork can often stay in place for a backup or for rooms the mini split doesn't reach, though some homeowners pull the ductwork out entirely once it's no longer doing the main work. A window unit or old split system gets disconnected and hauled off, and the refrigerant inside has to be recovered properly rather than vented, so that's part of the removal, not an afterthought. Whatever came out of the wall leaves a hole or a mounting mark behind, and patching that is worth asking about before the work starts, since not every contractor includes it.
