Assessing the environmental impact of software

Efficiency Angel

Article from Issue 258/2022

Germany created Blue Angel, the world's first eco-label for software, back in 2000. The methodology behind Blue Angel could serve as a model for other countries as governments turn their attention to the environmental impact of software.

It is one of those annoying things that I hope consumers will never get used to, nor should they accept it. A device that costs a large amount of money is suddenly no longer of use simply because the required security update is not available. Or perhaps the new application software needs more powerful components or the interfaces are incompatible with other devices? In all these cases, consumers have no option but to replace devices that are actually still working. In other words, the software forces an unnecessary upgrade to the hardware. This common scenario can lead to significant waste of energy and raw materials.

The greatest environmental impact from information and communications technology products happens during the manufacturing process. A rumor still persists that replacing existing technology with more energy-efficient technology is good for climate protection, but the truth is, considerably higher CO2 emissions are produced during manufacture of that "energy efficient" device than during use, so in many cases, the best thing you can do for the environment is keep using the device you already have rather than drive demand for more production.

Now you could argue that short replacement cycles would not be so bad if accompanied with an effective program for recycling. But, in practice, recycling processes do not exist for some metals, which means that valuable materials are irretrievably lost when you throw away a computer. Large quantities of electronic scrap ends up in landfills.

Until now, the focus of regulation, research, and manufacturer activities has been exclusively on hardware. Environmental labels, voluntary commitments, and minimum legal requirements created the foundation on which laptops, computers, and monitors were able to become significantly more energy efficient in recent years.

Unfortunately, a similar success story cannot be told when it comes to software. Certainly some software is developed by teams that place an emphasis on long service life, but this is by no means true of all software products. Negative examples include programs that force you to disable the computer's power management to avoid data loss, applications that become so bloated with updates that they respond to commands very slowly or crash frequently, and software that consumes more energy than is actually necessary. This list of bad features could easily go on.

Keep in mind that there are software features that reduce the environmental impact during use. The design of the software architecture determines how much hardware and electrical energy you need. For example, depending on how intelligently it is programmed, the software might require less or more processing power and memory. Figure 1 illustrates the various effects that software has directly on hardware and indirectly on the environment.

Figure 1: Model for understanding the effects of software on the environment. All phases of the software lifecycle can have an effect on hardware usage. © ETH Zurich

The path of the search for effective environmental criteria has been rocky and difficult. Why has software flown under the radar until now? Why is there so little research and regulation on this subject? There are at least two crucial reasons for the lack of attention to software's environmental effects. On one hand, the relationship between cause and effect is far less easily discernible for software than for hardware, making it difficult to set verifiable minimum requirements. On the other hand, the large number of different software products and areas of application make it difficult to assess the full scope of the problem.

In spite of the obstacles, the German government is currently developing a methodology that will allow it to rate software for its environmental impact. The Blue Angel eco-label developed by German scientists could serve as a model for similar rating systems in other countries.

The Research

In a recent research project [1], Germany's Federal Environment Agency, in collaboration with the ÷ko-Institut, the Environmental Campus Birkenfeld of the University of Trier and the University of Zurich, initially undertook a classification of various software products (Figure 2). With the help of this classification and a detailed impact model showing the interactions between hardware and software, the researchers developed a catalog of criteria for sustainable software. In total, the catalog lists 76 individual criteria, which it groups under three categories: resource efficiency, influence on the duration of the hardware use, and autonomy of use. Each criterion can be evaluated by reference to one or more indicators.

Figure 2: Classification of application software.

The project developed an evaluation and measurement methodology that you can use to determine the energy requirements, hardware resource usage, and other environmental characteristics of software. The research report examined software products with the same functionality from four different product groups to assess the methodology. In a standard scenario, in which the typical functions run automatically in a defined sequence, the differences between the software products were very much apparent (Figure 3). The energy consumption of the least efficient software (bottom) is four times higher than that of the better-performing product (top). The difference in energy usage is particularly relevant in light of the fact that excessive use of hardware in the inefficient candidate leads to slower execution. In a worst-case scenario, the user will just throw away the computer and replace it with a newer, faster model, when all they really needed to do was replace the software.

Figure 3: Sample test result for two word processing programs.

The First Eco-Label

Germany's Federal Environment Agency has used the results of this study to develop the Blue Angel eco-label for software. To be eligible for the Blue Angel, software must still run on a computer that is at least five years old and ensure security updates for at least five years. It must not interfere with the computer's energy management, and it must disclose the data formats, so that future use of the data is possible. In addition, the applicant must disclose the software's energy consumption and hardware resource utilization test results. To this end, the German government has developed a test method, including software that can be used to determine energy consumption data and hardware utilization.

The first version of the eco-label imposes requirements for local application software (software intended for computing and storage on the local computer). Ongoing research projects will expand the scope of Blue Angel certification to include distributed software and applications for smartphones or tablets.


With the results of its research, the Federal Environment Agency has opened up a view window onto the environmental impact caused by software. But the real challenge is not to rate the software after it is created but to provide the information necessary for developers to make the right decisions early in the software planning and development phase, supporting optimized tools and methods that result in environmentally friendly software.

Another project of Germany's Federal Environment Agency, the SoftAWARE Research project, launched in 2021, is intended to contribute to the goal of encouraging more sustainable software design. The project, which is a collaboration with the Sustainable Digital Infrastructure Alliance and the ÷ko-Institut, will examine the energy efficiency and resource efficiency of programming languages, components, and container classes. This work should enable developers to create more energy-efficient and hardware-friendly software. This task will require information about the energy consumption and hardware usage of software components, as well as development tools, optimization information, and recommendations for an improved energy efficiency index. The project will also sponsor a hackathon next year to find solutions to documented problems and to award prizes to the most energy-efficient software solutions.


  1. Development and application of evaluation principles for resource-efficient software:

The Author

Marina Köhn is a computer scientist who has worked as a researcher with Germany's Federal Environment Agency since 1992. Her work focuses on environment-related system comparisons, particularly in the field of information and communication technology (ICT). Köhn has been working on issues relating to green IT for over 20 years. As part of this activity, she participated in developing the Blue Angel system and other methods for measuring the energy and resource efficiency of data centers, cloud services, and software.

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