Mostly from coal...some from solar...some from nuclear. Not from oil or petrochemical...which is Texas's mainstay.
Wow you have no clue how diverse the energy portfolio is in Texas and where electricity comes from.
Coal is on the way out due to the low cost of nat gas and excessive and intrusive EPA regulations from the Obama administration. More and more coal is being sold over seas to countries like China.
Old coal fire plants are being retooled or demolished and rebuilt for nat gas. see the FPL plant in Florida a few weeks ago.
Texas has vast nat gas reserves.
Texas is one of the largest wind power states (disclosure I am a wind tech)
Solar power accounts for less than 1% of all power put on to the grid.