I was recently interviewed by IEEE Spectrum for the article: The 5G Dilemma: More Base Stations, More Antennas—Less Energy?
Since 5G is being built in addition to the existing cellular networks, the energy consumption of the cellular network infrastructure as a whole will certainly increase when 5G is introduced. It is too early to say how much the energy consumption will grow, but even if the implementation would be vastly more energy efficient than before, we need to spend more energy to gain more in network capacity.
It is important to keep in mind that having a high energy consumption is not necessarily a problem. The real issue is that the power plants that power the cellular networks are mainly extracting energy from non-renewable sources that have a negative impact on the environment. It is the same issue that electric cars have – these are only environmentally friendly if they are charged with energy from environmentally friendly power plants. Hence, we need to keep the energy consumption of cellular networks down until cleaner power plants are widely used.
If you want to learn more about energy efficiency after reading the article in IEEE Spectrum, I recommend the following overview video (you find all the technical details in Section 5 in my book Massive MIMO networks):