When the mobile industry talks about 5G, the discussion is usually focused on the capacity gains and the lightning fast speeds it will deliver. But achieving those 5G benefits requires more macro cell sites as well as small cells, and that equates to increased power consumption and higher energy costs for mobile operators.

But most wireless carriers are so focused on their 5G deployments they haven't stopped to consider the amount of power required to fuel their networks. Chris Antlitz, principal analyst with Technology Business Research, said that energy cost is a big problem that doesn't get talked about very much. "These active antennas in the massive MIMO box require a lot more energy than a traditional eNodeB," he said.

In fact, it takes nearly double the amount of energy to power a 5G cell site using a massive MIMO antenna than it does a 4G cell site. According to Chris Nicoll, principal analyst with ACG, a 4G cell site currently uses about 6 kilowatts to power a three-sector, 12-radio antenna. A 5G cell site using massive MIMO technology uses 10 kilowatts of power.

Energy costs for operators have always been fairly substantial. In an April 2019 blog post, Nokia estimated that mobile operators have racked up over $78 billion in radio access network energy costs.

Nicoll added that the power requirements for wireless networks have been on the rise for many years – even before 5G. He said that over the past 20 years the energy requirements for wireless networks have increased tenfold. And with 5G massive MIMO, those energy requirements will likely double again in the next couple of years.

And it's not just massive MIMO antennas that are causing the big jump in power requirements. Antlitz noted that many operators plan to use mini data centers at the network edge or at cell towers. Those edge computing sites will need electricity. "The amount of energy is increasing, and not just from the radio resources but also from the compute side, which will be transmitting into the sites."

Small cells, big power
Small cells also play a role in increased energy costs. Brian Daniels, senior VP of strategic networks at Zayo Group, which has been building a network of small cells on top of its fiber lines, said that his company works with the power company on every small cell that it builds. "If you add nodes to the network, whether those are macro cells or small cells, you have to power them," Daniels said.

But Daniels added that so far, he hasn't heard of any operators having concerns about power costs. Instead, he thinks they are focusing solely on getting the radios and baseband units deployed for 5G. "As 5G networks evolve, it's logical that the cost will become a bigger issue and the pressure will be put on the equipment makers to become more efficient with space and power," he said.

More efficient cell sites
To their credit, vendors have already been working on making cell sites more efficient. Nicoll said that 5G standards include a "Lean Carrier" specification that is intended to reduce energy consumption by up to 60% over legacy 4G networks.

Nokia is trying to help rein in energy costs for operators and has said that its AirScale basestations consume 60% less energy than some of its earlier models.

Likewise, Ericsson has said that its Ericsson Radio System radios and RAN compute systems can save operators up to 15% to 35% on power consumption.

Nicoll also said that while massive MIMO site technology dramatically scales up the power requirements, the corresponding power per bit drops. "The sites become more power efficient in delivering bit rates that are three to ten times higher than 4G," he said.

But not only is the cell site equipment more efficient, it also doesn't necessarily have to be running 24 hours a day, seven days a week. Nicoll said that equipment makers are looking at ways to minimize energy consumption in certain traffic conditions. For example, Nokia said it is working on features that will put certain parts of the network to sleep when it has a lighter load. Nokia said that these types of features can reduce energy consumption from 10% to 20%.

— Sue Marek, special to Light Reading. Follow her @suemarek.