Energy consumption of network communication

System boundaries

The system boundaries are set differently depending on the study.

Examples of different system boundaries:

mobile network: data transfer between base station and end-user device
data exchange between data centers
internet traffic / transmission network: data transfer between a data center and a end-user device (data center and end-user devices are excluded; differentiation between fixed-line and mobile access is important)

See also the network categories defined by the Technology Carbon Standard:

operational network
backbone internet
public wireless networks
client network

Energy consumption of internet data transfer

Data transfer != network energy usage

Often the metric kWh/GB is used to calculate the energy consumption of network transfer. However, there is no correlation between the amount of transferred data and energy consumption!

→Energy consumption per transferred data is a bad metric

Methodology of the tool Cloud Carbon Footprint

Networking

Source: https://www.cloudcarbonfootprint.org/docs/methodology/#networking (accessed on 2024-01-29)

Currently, our application takes into account only the data exchanged between different geographical data centers.
For networking, it is safe to assume that the electricity used to power the internal network is close to 0, or at least negligible compared to the electricity required to power servers.

[…]

There have not been many studies that deal specifically with estimating the electricity impact of exchanging data across data-centers. Most studies focus on estimating the impact of end-user traffic from the data center to the mobile phone; integrating the scope of the core network (what we are interested in), the local access to internet (optical fiber, copper, or 3G/4G/5G) and eventually the connection to the phone (WiFi or 4G).

[…]

It is safe to assume hyper-scale cloud providers have a very energy efficient network between their data centers with their own optical fiber networks and submarine cable. Data exchanges between data-centers are also done with a very high bitrate (~100 GbE -> 100 Gbps), thus being the most efficient use-case. Given these assumptions, we have decided to use the smallest coefficient available to date: 0.001 kWh/Gb.

Appendix IV: Recent Networking studies

Discussions:

Include estimate of bandwidth leaving a data centre · cloud-carbon-footprint/cloud-carbon-footprint
Research coefficient for networking of data leaving a data center · Issue #379 · cloud-carbon-footprint/cloud-carbon-footprint
Intra-Region network energy/data transfer coefficient is unclear in the documentation · Issue #951 · cloud-carbon-footprint/cloud-carbon-footprint
Networking for traffic leaving a data center · Issue #723 · cloud-carbon-footprint/cloud-carbon-footprint

Data exchange between data centers of the same hyper-scale cloud provider:
0.001 kWh/Gb

Aslan et al. (2018)

Scope: Transmission network

aslan.etal.2018.electricityintensityinternet (comment) (pg. 3)

Transmission network = IP core network (e.g. core/metro/edge switches and routers) + access network (e.g. DSLAM)

Not included: undersea cables, data centers, home/on-site network equipment, user devices

Aslan et al. estimate that data transmission costs decrease by 50% every two years.
Quote:

aslan.etal.2018.electricityintensityinternet (pg. 13)

Estimates for average transmission network electricity intensity that meet these criteria show a halving of intensity every 2 years.

stephens.etal.2021.carbonimpactvideo (pg. 21)

Aslan’s rule
Analysis of estimates for the average electricity intensity of fixed-line internet transmission networks for data transfers from 2000 to 2015 concluded that electricity intensity (in kWh/GB) decreased by half approximately every two years over that time period (Aslan et al., 2018).

stephens.etal.2021.carbonimpactvideo (comment) (pg. 42)

Fixed network energy intensity (2020) = 0.0065 kWh/GB
Mobile network energy intensity (2020) = 0.1 kWh/GB
Home router energy intensity (2019) = 0.025 kWh/GB

Numbers based on Aslan's rule

Formulas:

$0.06 \times {0.5}^{\frac{year - 2015}{2}}$
$Value of year before \times \sqrt{0.5}$

Year	kWh/GB
2015	0.06
2016	0.042426407
2017	0.03
2018	0.021213203
2019	0.015
2020	0.010606602
2021	0.0075
2022	0.005303301
2023	0.00375
2024	0.00265165
2025	0.001875
2026	0.001325825
2027	0.0009375
2028	0.000662913
2029	0.00046875

Andrae (2020)

Wireless access network: 0.18 kWh/GB
Fixed access wired networks: 0.07 kWh/GB

Energy consumption of mobile cellular communications

@Golard.etal.2023.EvaluationProjection4G5GRANEnergyFootprints

Projection for Belgium for 2020–2025 of radio access networks (RAN):

Energy intensity of 4G only in 2025: ~0.15 kWh/GB
Energy intensity of 5G only in 2025: ~0.01 - ~0.06 kWh/GB
Carbon intensity in 2025 with 4G & 5G: 0.05 kgCO2e/GB

@Pihkola.etal.2018.EvaluatingEnergyConsumption

Mobile network in Finnland:

2016: 0.5 kWh/GB
2020: ~0.1 kWh/GB

Energy efficiencies of different networks

Embodied Carbon

Embodied Carbon of Network Infrastructure

Footprint of unwanted data transfer

Energy consumption of advertisements

Carbon footprint of unwanted data-use by smartphones (Uijttewaal et al.)

uijttewaal.etal.2021.carbonfootprintunwanted (pg. 12)

we estimate that the yearly carbon footprint of data-use by advertising and tracking services in smartphone apps in Europe is between 5 and 14 Mt CO2-eq.

Data used by website carbon calculators

The calculation model of SustainableWebDesign.org that is used by the CO2.js library and multiple website carbon calculators not only includes the energy used by the IP network, but also the energy used by consumer devices, data centers and the production of the hardware components.

See SustainableWebDesign.org#Emissions Calculation Formulas for more information.

Videostreaming

Climate emissions of videostreaming