LAFs From Industry Standing Data

2026-03-28

In a previous post I talked about distribution losses, and using the LAF (Loss Adjustment Factor) to find the GSP kWh from the MSP kWh:

(GSP kWh) = (MSP kWh) x LAF

There's a published LAF for every half-hour for every LLFC for every DNO, which is an enormous amount of data. Chellow used to try and import only the ones it needed, but that got too fiddly so now we just import the whole lot. The LAF files from the Elexon Portal in the PTF format look like:

The LAF files can be retrieved from the Elexon Portal in two ways, API and manual download. The API method is preferable because it can be automated, so that's Chellow's primary method. The call to the API is of the form:

https://downloads.elexonportal.co.uk/svallf/download?key=8jrjfglsjkjj&ldso=LDSO&format=SPF|PTF|UFF|SUM

The drawback is that you can only download the LAFs for the current financial year, but we want to load all the available LAFs for future years for forecasting. So to get future years we turn to the manual download page:

We manually download the files we need and then put them onto the Rate Server which all Chellow instances then automatically download from.

That all works, but it always bothered me that there was a manual step. Looking at the Industry Standing Data (which replaces the Market Domain Data, I saw that it contains the full set of LAFs.

I've made a start on getting Chellow to use the ISD, but it's still a work in progress. There's an API where you can call:

https://datastore.helix.elexon.co.uk/api/ISD

and it'll download the full set of data. My plan is to get Chellow to automatically check every few days for a new version and then import the LAFs if a new version has come out. In time we'll use the ISD to completely replace the Market Domain Data, and that'll be another step forward for automation.

See you next time! ✨