The buses are in addition to the 150 articulated hybrid buses already in its fleet.
"With the budget challenges we face we are constantly seeking ways to be more cost efficient. These hybrids represent significant savings. Once all 58 hybrid buses are in service, the CTA will have a total of 208 articulated hybrid buses in its fleet," said CTA President Richard Rodriguez.
The CTA says hybrid buses are quieter, cleaner and run more smoothly.
It's estimated that the hybrid technology will help save the agency more than $7 million annually.