While the cost of running an AM or DAB station is roughly the same, broadcasting is far more expensive for both AM and FM.
Analogue stations are broadcast on separate radio waves, whereas DAB channels can be grouped together as they are broadcast into what is known as a “multiplex”. Each AM and FM frequency carries only a single station, whereas DAB multiplexes each carry between 11 and 22 stations, making it much more efficient.
As a result, AM and FM networks need more infrastructure than DAB to broadcast the same number of stations, and therefore use more energy. Around three-quarters of energy use in the UK radio industry comes from power-hungry analogue broadcasts, despite the fact that the majority of listening is digital.
AM is also much more expensive than FM because the older technology is less efficient. Radio expert James Cridland says…
