An environmental figure appears to conclude a discussion. However, it changes when the boundary changes: network or transaction, page or project, operational electricity or manufacturing. The issue is not that every estimate is useless, but rather the comparison of figures produced with different boundaries.
Before comparing, one must define the system
A work may involve manufacturing, electricity, data centres, networks, devices, storage, travel, transport, materials, maintenance, and end-of-life. No examined calculator automatically gathers all these layers and attributes them to a work.
Ethereum: a real architectural shift
Ethereum executed The Merge on 15 September 2022 and replaced proof of work with proof of stake. Ethereum.org attributes an approximate 99.95% reduction in network consumption to this change.
The figure describes Ethereum, not every blockchain or every activity associated with a work.
An estimate is not a meter reading
Ethereum publishes an approximate estimate of 0.0026 TWh per year, derived from a CCRI study based on node configurations. The result changes with nodes, hardware, clients, and electrical intensity.
From the network to a work
Distributing annual consumption across transactions produces a communicable figure, but not a direct physical measurement of the consumption caused by a work. It may serve as an accounting rule if the method is declared.
Web calculators use proxies
The Sustainable Web Design Model estimates emissions based on data transfer and distributes energy between data centres, networks, and devices. Its version 4 includes operational and embodied components. It does not measure the actual electricity of each visit.
Changing the version changes the result
Version 4 updated sources and the formula. The Green Web Foundation notes that it produces estimates approximately two-thirds lower than version 3 in equivalent comparisons. Website Carbon adopted v4 in July 2025 and CO2.js uses it by default.
A website may obtain a lower figure without having changed if different versions of the model are compared.
Website Carbon and CO2.js may share a model
Obtaining similar figures with both tools does not constitute two independent validations if they share SWDM v4. The useful comparison is to repeat the test with the same tool and version after an intervention.
The art sector prioritises other sources
The Gallery Climate Coalition prioritises travel, artwork transport, and building energy, and adds materials and digital activity. Its calculator does not automatically distribute the manufacturing and end-of-life of each screen among specific works.
A work does not coincide with an organisation
Attributing an institution's emissions to a work requires a rule: exclusive or shared use, hours, surface area, visitors, transfer, lifespan, travel, and transport. Each rule answers a different question.
The digital is not immaterial
Transfer activates data centres, networks, and devices. However, adding the entire manufacturing of a piece of equipment to every work duplicates the same burden. The embodied footprint requires a lifespan and an allocation criterion.
Publish the method alongside the figure
A declaration should include the object, period, boundaries, model, version, measured and estimated data, electrical intensity, manufacturing, assumed use, exclusions, and uncertainty.
What the cases do not demonstrate
The fall of Ethereum does not render any use of blockchain irrelevant. Web calculators do not measure the total footprint of a work. Renewable hosting does not eliminate networks, devices, or embodied emissions.
To take action
The guide The environmental footprint of a digital work allows for the inventorying of sources and the declaration of boundaries. This article also links to Mass technology and ethical consumption.
About the open conversation
It remains to be determined which boundaries, models, and data should accompany an environmental figure so that it may be interpreted and compared. What is included in the scope and what is excluded? How is a direct measurement distinguished from an estimate?
An isolated figure does not allow for the comparison of projects if the method, date, and exclusions are unknown. An estimate, however well-constructed it may be, is not equivalent to a direct measurement.
If you have measured the footprint of a project or an exhibition and are able to share the method, date, scope, and exclusions, this notebook remains open: write to me. Without such data, an isolated figure provides little insight.