FWIW, you probably want a soft wash not a true power wash. I'm in 77007, we had someone soft wash our house about 5 years ago and they did a really good job, but needing it again soon. Trying to dig through my email to find the company.....
I'm in 77008 and ironically got this flyer on my gate yesterday. No idea if they're any good or not but they do say their exterior house wash is a low pressure soft chemical process.