TDU Delivery Charge: TDU stands for transmission and delivery utility — in other words, the utility company in your area that is actually piping the energy from the power generation companies into your home. (Remember, REPs in Texas are just the middleman.) The TDU delivery charge is set by the utility and is consistent from plan to plan and provider to provider within its service areas. For example, AEP , the TDU for Corpus Christi, charges the same delivery fee for all TXU, Direct Energy, and Reliant plans. You don't typically get a choice in utility company, and therefore, these fees are pretty much unavoidable, non-negotiable, and won't factor into choosing an electricity plan or provider.
As you choose your energy plan, you might want to consider a variable-rate plan. The wholesale price for electricity changes constantly and a variable rate allows you to take advantage of its ups and downs. When prices are low, your electricity rate can drop to reflect the market change. On the other hand, electricity prices can rise, causing you to pay a higher rate.
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.
Compared to the rest of the nation, data from the U.S. Energy Information Administration which publishes annual state electric prices  shows that Texas' electric prices did rise above the national average immediately after deregulation from 2003 to 2009, but, from 2010 to 2015 have moved significantly below the national average price per kWh, with a total cost of $0.0863 per kWh in Texas in 2015 vs. $0.1042 nationally, or 17 percent lower in Texas. Between 2002-2014 the total cost to Texas consumers is estimated to be $24B, an average of $5,100 per household, more than comparable markets under state regulation. 
1Offer valid for new residential customers in Texas only. Provisioned smart meter required. Free power begins on Fridays at 6:00 PM and ends Sunday at 11:59 PM. To utilize all features of the Echo Dot, you will need an 'always on' Wi-Fi internet service. If you cancel your plan early there's a fee of $135. You cannot return your Echo Dot to avoid the early cancellation fee. Terms and Conditions apply. All Amazon trademarks and copyrights are property of Amazon.com or its affiliates. The Echo Dot is provided by Direct Energy, Amazon is not a sponsor of this energy plan offer.
Variable-rate plan:A variable-rate plan means the rate you pay for your electricity may fluctuate based on the market price of energy. Energy price depends on many factors, like weather, demand, fuel prices, the distribution system and the market. Variable-rate plans are flexible because you are not locked into a contract; however, you’ll pay a higher price in high-demand seasons like summer. A variable-rate plan might be ideal for you if you like to shop around and keep an eye on prices.
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.