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Introduction to the API


The ETM API is versioned as v3, but at the time of writing is not semantically versioned. While we seek not to change the public API in a way that would break clients, it's nonetheless constantly in development.

All paths to the API are prefixed with /api/v3.


We operate two versions of the ETM. You should almost always use the production environment unless you have a specific reason to use staging.

EnvironmentEndpointGit branch


This is the standard version of the ETM. Features area generally complete, well-tested, and ready to be used by the general public. We aim for the production environment to be available 24-hours a day and 365-days a year, except during occasional, short periods while we perform updates.

We intend to store owned scenarios created on the production server forever.


The staging environment is used to test new features before they are ready for the general public. While this means you can get access to access to cutting-edge features earlier, results from the staging server are subject to change. Scenarios made on the staging environment cannot be transfered to production, and vice-versa. Your settings and user account from the production server do not carry over to the staging server; you need to create a separate account.

We have no plans to delete scenarios from the staging server, but we reserve the right to do so including owned scenarios.

The staging environment may occasionally be unavailable.

Response status codes

As a REST API, the Energy Transition Model uses a range of status codes to indicate the success or failure of the request.

200 OKThe request was successful.
201 CreatedThe request was successful and a new resource was created. Note that a number of API endpoints use 200 OK instead.
400 Bad RequestThe server was not able to process the request due to it being malformed.
401 UnauthorizedThe request was rejected due to not having permission to access the resource.
404 Not FoundThe resource requested does not exist at the current time.
406 Not AcceptableThe Accept header did not specify a content type which can be generated by the server.
422 Unprocessable EntityThe request was correctly formed (unlike a 400 Bad Request response), but contained errors which prevent it from being accepted. Typically an "errors" parameter will contain more information. See Errors.
429 Too Many RequestsThe request was rejected due to exceeding the API rate-limit. At the time of writing, the ETM has no rate-limits; while there are no plans to change this, but your application should be prepared.
500 Internal Server ErrorAn error occurred with the ETM.


Some endpoints return paginated data – where there are too many items to show at once. Examples include the scenario and saved scenario lists. To get the full list of items you must iterate through all pages.

Paginated responses contain three keys:

  • data - an array of items, such as scenarios or saved scenarios
  • meta - information about pagination, the number of items in the data array, the total number of items belonging to you, etc.
  • links - links to the first, previous, next, and last pages in the set


  • limit - the requested limit for how many items should be included on each page of results
  • count - the number of items on the current page; this may be lower than limit when viewing the last page of results
  • total - the total number of items which belong to you
  • total_pages - the total number of pages of items
  • current_page - the number of the current pages
  • first - link to the first page of items
  • prev - link to the previous page of items, or null if you are on the first page
  • next - link to the next page of items, or null if you are on the last page
  • last - link to the last page of items


Many endpoints within the ETM will respond with useful error information if the received request could not be processed. This will be in the form of a 400..499 response code, and a JSON response containing an errors key.

HTTP/1.1 422 Unprocessable Entity
Content-Type: application/json; charset=utf-8

"errors": [
"Curve must have 8760 numeric values, one for each hour in a typical year",
"Curve must only contain numeric values"
"error_keys" attribute

Some endpoints also provide an error_keys attribute – used for localization on official ETM websites. This attribute is not considered stable, and may be subject to change in the future. Please do not rely on it in your own applications.