The other possibility is that your A/C units are old and inefficient. Many of the houses were built in the 70s-90s, and their A/C have been repaired instead of replaced when required. The minimum SEER is now 15, while the original units were probably 10-12 at best, and you can get as high as around 25. Whether this has a good economic payback is doubtful, but you can get better dehumidification and comfort. There are also good cold temperature heat pumps with Federal income tax rebates available.

My first summer in Texas, I had a $450 bill. I was on a Reliant month-to-month plan (very expensive), one A/C I upgraded after moving in, as the old unit wasn't working, and I wasn't going to throw good money into an old unit. I got a cheaper electrical plan. I also had an old, inefficient pool pump. I replaced the second unit a couple years later, and got a more efficient pool pump. My highest bill this year was $240. The insulation is still inadequate, and more air sealing would help get this a little lower. The windows are also inefficient, but until more of them are foggy, I'm holding off on them, as there's a limit to the return.

Ideally, the first step is to sign a contract for a cheaper electric plan. Stay away from the gimmick "free nights and/or weekends". Next is to air-seal the house and add insulation if needed. Then, you may be able to get smaller A/C units, since there is a lower heating and cooling load, if the HVAC runs an honest Manual J calculation, instead of replacing capacity. A heat pump might force a bigger unit than A/C alone. This might also drive the need for a variable speed A/C, to prevent short-cycling of the equipment in Spring and Fall, as the A/C will be oversized. Once everything has been done, you can consider Solar, but the way the rates are set, Texas doesn't have compelling rates to make solar have a very short payback.