Electricity rates in Texas are not fixed. Your rate can vary greatly depending on your usage and your electric plan. Some plans have relatively flat rates, while others can be all over the place. This means that you could end up paying 7¢ for 999 kWhs and 8.5¢ for 1001 kWhs. That would be a 16% increase because you microwaved a few potatoes. Learn more on the different plan types here.
The PUC’s mission is to protect customers, foster competition, and promote high-quality infrastructure. In addition to regulating the states electric utilities and implementing legislation, the PUC offers Texas residents assistance in resolving consumer complaints. If you have a complaint with your electricity company you can go to the official PUC website and file an informal complaint.