In a recent interview, the Flemish minister of Media mentioned energy efficiency as one of the advantages of DAB+ digital radio over FM radio. (And thus making the decision by the EU to completely switch over to digital radio in the next few years seem ecologically motivated.)
Asked about the (slowly) growing number of DAB+ users, he is reported to have said:
"Dit bewijst meer dan ooit dat DAB+ de toekomst van radio is: betere kwaliteit, groter gebruiksgemak, een ruimer aanbod, zuiniger qua energie, ..."
which translates as:
"This proves more than ever that DAB+ is the future of radio: higher quality, better user-friendliness, a greater choice [of stations], better energy efficiency, ..."
However, an analog radio set is one of the least energy-hungry appliances you'll find in your house; small portable radios and radio alarm clocks sometimes work for several years on a single set of batteries, and you can even build a radio set that doesn't need batteries at all.
Digital radio sets, on the other hand, necessarily contain a processor and DA convertor; a quick search tells me that the power consumption of the most frugal DAB+ radio sets is around 3.5W at the moment.
Therefore it seems unlikely that this claim is true, at least not when looking solely at the receivers.
Is there a way of measuring the power consumption of radio, e.g. by not only looking at the receivers but also at the power consumption of transmitters, that would make the claim that digital (DAB+) radio is more energy efficient than FM radio true at this point in time?