The cost of the energy needed to power 5G is shaping up to be one of the biggest headaches for operators rolling out the new networks.
Experts believe that a 5G network will consume three and half times as much electricity as 4G, thanks to a combination of massive MIMO antennas, legacy networks in multiple bands and the massive proliferation of small cells.
Jake Saunders, the managing director at ABI Research, says a typical LTE cellsite today might draw about 6 kilowatts (kW) in power, rising to perhaps 8-9kW at peak traffic periods.
In five years, a 3.5GHz site deploying massive MIMO with four transmitters and four receivers (so-called 4T4R) might draw 14kW on average and up to 19kW under peak load, he said.
"In that scenario, the basestation will be also supporting 2G, 3G and 4G as well, in as many as seven different bands from 700MHz up to 3.5GHz. That's where you're seeing the multiplication take place," he said.
Beyond that, another two or three times as many small cells sites will have to be deployed in order to achieve full 5G coverage and throughput.
A Huawei analysis based on operator data draws similar conclusions.
The power consumption of 5G equipment in 3.5GHz, with 64T64R and massive MIMO, will be "300% to 350%" of a 4G basestation, it says.
It says a cellsite today deploying 2G, 3G and 4G in five different bands will on average consume 5.9kW in power, with a peak of 7.3kW.
In three years, with the addition of 5G equipment in 2.6GHz and 3.5GHz bands, this will almost double to an average of 10.4kW, with 13.7kW during peak periods, Huawei predicts.
In five years, following the deployment of mmWave, this will rise to 13.4kW on average and 18.9kW at peak times.
The steep rise in energy consumption is a problem that is vexing Chinese operators, which have already deployed around 80,000 basestations and will formally launch 5G service on Thursday. (See China Operators Head Into 5G With Lackluster Results.)
Huawei estimates that by 2026 Chinese operators will have deployed 4.75 million 5G macro basestations and another 9.5 million small cells using mmWave.
Yan Binfeng, director of the technical committee of China Unicom Research Institute, agrees that the 5G power bill would be more than three times that of 4G.
The state cell tower company, China Tower, has forecast that the electricity cost of 5G basestations is about ten times the annual rent, the IT Home website has reported.
Some regional governments keen to see 5G rolled out quickly are now offering electricity subsidies.
Jiangxi province authorities are offering a power subsidy of RMB8,000 ($1,134) this year for every additional basestation built beyond a baseline target, with further subsidies in 2020 and 2021. Shenzhen city and Shanxi province are also subsidizing 5G electricity costs. (See China Telcos Rack Up 9M 5G Advance Subs.)
Saunders said the 5G power consumption and cost "is a complex one, and I think operators are only just starting to fully digest it."
He expected some telcos would ditch their legacy 2G and 3G technologies to help manage the power load.
"I think over time the solutions will become more cost-effective, but massive MIMO does require an awful lot of power. It will take a number of generations before we can get substantial energy savings built into the silicon," he said.
But he also notes that in the next few years operators are likely to start deploying mobile edge computing, which could mean extra significant power loads at the edge and a new problem to solve.
Ericsson said in a statement that while massive MIMO consumes more energy as more antennas are deployed, legacy networks "will by far consume the largest share of the energy used."
Despite that, it says that massive MIMO, which extends coverage and capacity and can quickly change between low and heavy loads, is important for efficient energy consumption, along with ultra-lean designs that allow basestations to sleep during off-peak periods.
— Robert Clark, contributing editor, special to Light Reading