The report by the CNMC means households may be required to alter their TV aerials and retune their sets.
DTT currently represents 76% of viewing time in Spain.
The government now plans to fast track the process to allow it to take place before June 2020. The freed capacity will then be offered to mobile telephony operators to use for 5G mobile services.
DTT will move to the 470-694 MHz band that will be guaranteed 2030. Its hoped to maintain the current service with enough capacity for 4 high definition channels in each multiplex. Channel providers will be able to continue to offer standard definition channels through to 2023.