3.1. Overview of the conventional approach

Characteristics

• Utilises average transmission network energy intensity estimates derived from academic literature

• Relies on an allocation approach to attribute the energy consumption of a shared network to the services that use the network

• Transmission network energy consumption is allocated to streaming based on data volume transmitted for one hour of streaming

• Data centre and user media devices energy consumption is allocated based on viewing duration

Intended use

• Organisational foot-printing for video streaming service providers

• Network/system level carbon footprint estimation

Strengths

9 Well understood and accepted by the industry

9 Accounts for all energy consumption across the network when scaled to network level

9 Straightforward accounting and allocation approach

Limitations

X Representative of a particular network and period of time

X Sensitive to characteristics of the transmission network considered for estimation. These network characteristics include network equipment efficiency, quantity of network users and data traffic

X Unsuitable for estimation of the marginal carbon impact due to a change in level of service, such as a change in video quality

The conventional approach may be described as an average energy intensity approach, as it utilises average transmission network energy intensity3 to estimate the network energy consumption attributable to video streaming. Furthermore, as the transmission network is an interconnected system of network users and services, the energy consumed by the network is shared among the various users and services that access the network. In order to divide the network energy consumption among the various users and services, an allocation approach is employed. In this case, the transmission network energy consumption is allocated based on the volume of data transmitted across the network by the video streaming service, hence the utilisation of transmission network energy intensity. An implication of this is that energy consumption of idle network equipment is allocated based on the internet service’s transmitted data volume, with higher bitrate services like video streaming receiving a larger share of idle energy. Other allocation approaches are conceivable, such as network energy allocation based on share of peak network traffic or based on duration of use, but allocation based on data volume is the typical focus in academic studies and therefore the most widely understood.

As the energy intensity is derived at the network level, the conventional approach is widely accepted as an appropriate estimation methodology for organisational foot-printing for organisations that provide internet services, such as video streaming providers, and if employed across an entire transmission network, would account for all of the energy consumed. This approach is also appropriate to use for a network or system level estimation of video streaming’s carbon footprint. For this study, the conventional approach has been adapted to estimate the carbon impact for one hour of video streaming. There are sensitivities and limitations to the conventional approach, which should be understood as well. The conventional approach is representative of a particular network and period of time. For this study, the parameters used are characteristic of mature transmission networks in 2020 such as those found in Western and Northern Europe. As networks are continually evolving, the parameters used in this approach should be updated to reflect the characteristics of the network during the period of time being evaluated. Transmission network energy intensities in particular are quickly outdated, as discussed in the preceding sections of this paper. Additionally, while the conventional approach is suitable for organisational footprinting purposes, it is unsuitable for estimation and analysis to assess the marginal carbon impact due to a change in level of service, such as comparing the carbon emissions of streaming in different resolutions. This is primarily due to the conventional approach’s reliance on average transmission intensities, which do not reflect the dynamics of network transmission equipment as network load changes.

3 Transmission network energy intensity relates the network energy consumed to a metric, in this case the data volume transmitted through the network. The unit of measure for transmission network energy intensity is kWh/GB, where kWh represents the energy consumed by the transmission network and GB represents the data transmitted over the network, in gigabytes. Transmission network energy intensity estimates are generally derived and published through academic literature using a top-down evaluation of energy consumption of a transmission network and the volume of data that is transmitted across the network over a specified period of time.