In this free market competing electricity retailers buy electricity wholesale from private power generators to sell at retail to around 85% of Texas residents. The partnership between generators and retailers is governed by the Electric Reliability Council of Texas, or ERCOT, which attempts to balance the power grid’s electricity supply and demand by purchasing small amounts of electricity at 15-minute intervals throughout the day.
When it comes to the electricity itself, there is no difference at all. A cheap electric supply is the same electricity, it's simply provided by a new supplier (unless you opt for green energy - more on that here). As suppliers buy and generate different sets of energy they also have different prices. What's more, you might be on a tariff that is simply more expensive, such as a standard tariff. If you decide to switch electricity don't equate a lower price with worse service.
Texas deregulated most of the state's electricity markets in 2002, a move aimed at lowering electricity costs by letting consumers choose their own electric power providers and their own plans. Some parts of Texas continued to be regulated, including those that get power from municipal utilities, electric cooperatives and investor-owned utilities that operate outside the state's primary power grid.