TXU is high because they charge their customers for the "fuel" to run their power plants - that's what the supervisor told us when we called to complain about my godmother's bill. Her actual usuage was $350 and they charged her an additional $350. And she didn't understand the bill so she had been paying it for months until we started looking at it. They are a rip off. Would never recommend them.
On the one hand, long-term, fixed-rate (contract) plans offer stability in pricing. If energy supply costs suddenly go up in your area, you won’t be left paying more than what you bargained for. You’ll have peace-of-mind. If you want to switch out of your contract before it ends with a lower cost plan, you’ll likely face a cancellation fee (early termination fee).