Sending a gigabyte costs a small and genuinely uncertain amount of energy — published estimates differ by more than a factor of ten — while storing that gigabyte for a year costs considerably more. That ratio is the only part worth acting on, and it points at deleting files, not at any choice about how you send them.
Why the numbers disagree so much
Look for "energy per gigabyte transferred" and you will find figures an order of magnitude apart. That is not sloppiness; it comes from real choices in how the question is asked.
What is counted? Only the network, or also the data centre, the home router and the screen showing the file?
Marginal or average? Network equipment draws power whether or not your file crosses it. The marginal cost of one more gigabyte is close to zero; the average — total energy divided by total traffic — is far higher. Both are defensible, and they differ enormously.
Which year? Efficiency has improved fast. Figures from a decade ago are wrong by a large factor today, and they are still quoted.
So anyone giving you one confident per-gigabyte number is more precise than the evidence supports — including anyone doing it to sell you something. For scale, the International Energy Agency puts all data centres together at around 1.5% of the world's electricity in 2024 (Energy and AI, April 2025). Real, and small. Everything below uses ratios, because ratios hold up even when absolutes do not.
The comparison that holds
Whatever figures you pick, one relationship survives:
Sending is brief. Storing is continuous.
A transfer uses energy for the minutes it takes. Storage uses energy every second the file exists — drives powered, plus cooling — for as long as you keep it.
525,600
Even if a stored file draws far less power per second than a transfer, a year of storage outweighs sending it once, and the gap widens every year.
Copies multiply the storage side. Three copies in three regions is three times the continuous cost. Nothing multiplies the sending side the same way.
What follows from that
Deleting beats compressing. Compression cuts both costs a little. Deleting removes them.
Short retention can beat renewable power. A service that deletes after a week can have a smaller footprint per file than one keeping everything forever on clean electricity, because duration multiplies whatever the source is. Both are worth having; only one is usually advertised.
Sending twice is cheap; storing twice is not. Re-uploading because a link expired feels wasteful. It is trivial next to keeping every file you ever sent.
Video dominates everything. An hour of ProRes runs to hundreds of gigabytes. Your whole email history is a rounding error next to one project archive. If you work in media, your footprint is your storage.
Keeping the scale honest
For one person this is small. Flights, heating, driving and making new devices dwarf it. Anyone presenting inbox-clearing as meaningful climate action is misleading you, and that framing does damage by making climate action look trivial.
Where it does matter:
- At organisational scale, where never-read data costs real money and energy and nobody owns the decision to delete.
- In media work, where storage per person is enormous.
- As a habit that pays three ways: deleted data costs nothing, cannot leak, and is what data protection law asks of you anyway.
What to actually do
- Cull before archiving. The near-identical frames, the six export versions. This is most of it.
- Give working files a shorter life than deliverables. How to choose the periods.
- Find duplicate copies. Backup, sync and archive often hold the same data three times without anyone deciding that.
- Prefer providers with short defaults and honest disclosure. Smaller effect, still worth ten minutes: how to check a green claim.
- Do not agonise over compression. Do it when it is free.
For file transfer specifically
Which service you send with is low-stakes environmentally. What to look for takes five minutes, and retention defaults are the figure worth comparing — they are documented in a way energy claims often are not.
Disclosure, since these pages are meant to be checkable: I run Yungle. It is hosted at Hetzner in Germany on hydropower, keeps one primary copy rather than three regional replicas, and free transfers expire after 7 days. Paid collections do not expire, which is worse on this axis and is something customers ask for. The rest is on the sustainability page.