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Reporting rules · Ontario

Data Centre Playbook and municipal pauses

Ontario does not ask you to report. It decides whether to approve you, and it decides on a water claim nobody can check.

Takes effect

Now

The playbook was released in August 2026. Oakville's one-year pause is approved. Mississauga voted in July to draft an interim control bylaw and it returns for a further vote in September 2026.

Who reports

Nobody. There is no reporting duty here at all.

No penalty attaches to the operator, because the duty is not theirs.

Claims register

Every figure on this page is recorded with its source in our public register, under C-022 and C-023.

Open the register →

What it actually requires

Read narrowly. Where the statute is narrower than the coverage suggests, the narrow reading is the one that governs.

  1. A facility taking more than 50,000 litres of water per day may require provincial authorization, depending on the circumstances.
  2. The province states it will target proposals that plan to use virtually no water during operation.
  3. Proposals using closed-loop cooling and reusing waste heat, for instance to warm nearby buildings, are prioritised.
  4. Oakville has approved a one-year pause on data centre development, the first Ontario municipality to do so. Mississauga's interim control bylaw returns for a further vote in September 2026.

What it does not measure

This is the part that decides whether the published number helps you or harms you.

  1. This is an approval preference, not a measurement requirement. Nothing obliges anyone to verify that a closed-loop claim is true.
  2. So the claim that wins you the approval is the same claim that, once you are operating, nobody is checking. That asymmetry is why the pauses happened.
  3. A council facing a room of residents cannot distinguish a genuine closed-loop design from an optimistic one, because the evidence to do so does not exist in either case.
  4. The 50,000 litre threshold is a taking figure. It says nothing about how much of that is returned, which is the number a community actually cares about.

What we would do about it

Meter both sides of the boundary, continuously, on the lines that matter. Close the balance every fifteen minutes: withdrawn, returned, reused, consumed, with the unmeasured paths shown as unmeasured rather than folded into an estimate. Sign each window and chain it, so the figure a council reads is the figure the operator reads and either can verify it independently.

It does not replace the filing. It gives you something to put beside it. Request a water assessment →

Questions people ask about Data Centre Playbook and municipal pauses

Short answers, because most of what circulates about these rules is wrong in the same two ways: who reports, and what gets counted.

Is there a moratorium on data centres in Ontario?

Oakville council has approved a one-year pause on data centre development, the first Ontario municipality to do so. Mississauga voted in July 2026 to draft an interim control bylaw for a one-year moratorium and it returns for a further vote in September 2026. These are pauses on approval, not reporting requirements.

Do data centres in Ontario need a water permit?

A facility taking more than 50,000 litres of water per day may require provincial authorization, depending on the circumstances. That is a threshold on water taken, and it is assessed as part of approval rather than reported continuously.

What does Ontario's data centre playbook say about water?

The province says it will target proposals that plan to use virtually no water during operation, and will prioritise closed-loop cooling and waste-heat reuse. It is an approval preference rather than a duty, and it carries no verification requirement.

How does a data centre prove a closed-loop claim in Ontario?

At present there is no established way to. The playbook prioritises closed-loop designs but requires no independent verification that a facility operates as claimed, which is precisely the gap that led municipalities to pause approvals rather than trust the submissions.

Why did Ontario municipalities pause data centre approvals?

Because approval turns on a water figure the applicant calculates themselves. A council cannot check it, the return side is rarely metered, and residents ask who verified it. Pausing is what a council does when it is asked to approve something it cannot assess.

Sources

We publish these because a page about a statute that cannot be checked is worth exactly as much as a water figure that cannot be checked.

This is a plain-language summary written by a company that sells water measurement, not legal advice. Read the instrument, and take counsel on how it applies to your facility.