How to tell if a service is actually green
Three claims get made using the same word, and only one of them means the electricity was clean: renewable supply, renewable-matched, and carbon-offset. Working out which one you are being sold takes about ten minutes and comes down to whether the provider names a supplier, a location and a figure — or whether it shows you a leaf.
The three claims, in descending strength
Renewable supply
The facility runs on renewable electricity, ideally under a direct supply arrangement with a named generator. The electrons powering the servers are clean, at the times they are consumed.
This is the strong version. Providers that have it tend to say so specifically, because it was expensive to arrange and they want credit for it.
Renewable-matched
The provider buys certificates equivalent to its annual consumption. The certificates are real and the market for them is real, but the generation may have happened elsewhere, at other times, and the facility may have drawn from a fossil-heavy grid at 3am in February.
This is the most common claim among large providers and it is a legitimate thing to do. It is not the same as the first, and it is usually described in language indistinguishable from the first.
The tell is annual matching. Ask whether matching is hourly or annual — hourly matching is substantially stronger and providers doing it will tell you.
Carbon-offset
The provider emits, then pays for reductions elsewhere: forestry, cookstoves, avoided deforestation. Offset quality varies from good to worthless, and the weaker end of the market has been documented at length.
This is the weakest claim and often the one dressed most enthusiastically. It is not nothing — but it is a payment made after the fact, not a change in how the service runs.
The five questions
Ask these directly. The quality of the answers separates real disclosure from decoration faster than any amount of reading.
1. Which data centre, and where? A named facility and country. Grid carbon intensity varies enormously across Europe, so the country genuinely matters. "Our servers are in the EU" is a jurisdiction answer, not an energy answer.
2. Who supplies the electricity, and on what terms? A named supplier and whether it is direct renewable supply, matched certificates, or offsets. Vagueness here is the single most reliable signal.
3. Is matching hourly or annual? If they know what you mean, that is informative in itself.
4. What is the PUE? Power usage effectiveness — total facility energy divided by energy reaching the computing equipment. Modern efficient facilities are near 1.1–1.2; older ones are much worse. A provider that does not know its own PUE is not measuring.
5. How long do you keep files, and how many copies? The question nobody expects, and the one with the largest effect. Storage is a continuous cost and replication multiplies it, so a provider keeping three copies forever has a much bigger footprint per file than one keeping a single copy for two weeks — whatever powers either.
Warning signs
A logo with no registry. Certifications worth having have public registries you can search. If you cannot look it up, it is a graphic.
"Carbon neutral" with no scope. Neutral across what? Scope 1 and 2 only, or including the supply chain and hardware manufacturing? The last is where most of it usually sits, and excluding it quietly is standard practice.
Tree planting as the headline. Planting trees is good. It is not a substitute for how a data centre is powered, and when it is the most prominent claim it is usually standing in for the absence of a stronger one. I say this as someone who gives a tenth of profit to rainforest protection — it is a thing I chose to do, not evidence about the electricity.
No figures anywhere. Substantive disclosure has numbers in it. Marketing has adjectives.
A sustainability page with no date. Claims go stale. An undated page tells you nothing about now.
Weighting the answers
Once you have them, the ranking that reflects actual footprint:
- Retention and replication — how long, how many copies. Largest effect, almost never advertised.
- Energy source — supply beats matching beats offsets.
- Grid location — real, second-order.
- PUE — real, smaller.
- Everything else — tree planting, carbon neutrality claims, badges.
That order is close to the inverse of how these things are usually presented, which is the useful takeaway.
Applying it
For file transfer specifically, what to look for walks through the same checks against this category, and the retention figures for the main services are documented and checkable even where energy claims are not.
And keep the scale in mind. Cloud storage is a real but modest share of anyone's footprint, and choosing a vendor carefully is a small act. The large one is on your side of the line: delete what you will never open again.
My own answers
Since I am asking you to interrogate providers, here are mine, checkable and unflattering where relevant.
One server in Germany, on renewable power. One primary copy, not three regional replicas — an efficiency choice that is equally an availability choice. Free transfers expire after 7 days; paid collections do not expire, which is worse for the footprint and is a feature people want. A tenth of profit goes to rainforest protection, which is a donation rather than a claim about electricity.
I do not publish a PUE, because I rent capacity rather than operate a facility, and quoting the provider's figure as though it were mine would be exactly the kind of thing this page is about.