A total of 31 states plus the District of Columbia offer online registration, and another 4 states have passed legislation to create online voter registration systems, but have not yet implemented them.”
According to the 2010 report, Online Voter Registration: Case Studies in Arizona and Washington, Arizona experienced a reduction in per-registration costs from 83 cents per paper registration to 3 cents per online registration. Other states have also experienced significant cost savings in processing registrations.
Implementation costs have in some cases been absorbed within existing budgets, been paid for with Help America Vote Act funds or have required one-time appropriations, ranging from $250,000 to $750,000 for more elaborate systems.
NCSL – Online Voter Registration
Bruce Elfant, Travis County Tax Assessor-Collector, said, “This year  it took our staff 12 days to process all the voter registration forms that were received at the voter registration deadline. Electronic voter registration would end this archaic process.”
Pass and implement online voter registration for Texas
Code – Election Code
Chapter – 31 Officers to Administer Elections
Section – 31.08 Collection of Information; Forum on Election Cost Savings