Former Comptroller Carole Keeton Strayhorn performed a study of the impact of illegal immigration in 2006. According to the Texas Tribune,
The results showed that if the estimated 1.4 million undocumented immigrants who lived in the state in 2005 were sent home, Texas would have lost about $17.7 billion in gross domestic product that year.
The population also produced more in-state revenue that year — $1.58 billion — than the $1.16 billion it cost in state services. Local governments, however, lost about $1.44 billion in combined health care and law enforcement costs that were not reimbursed by the state, according to the study.
In short, immigrants contribute more to the economy than they cost the state.