Reconciliations and NBP kWh

2025-11-01

If you have a complex pass-through tariff, you'll notice that after the initial charge for an element, you'll often get one or more subsequent charges. These subsequent charges can even arrive months after the contract has ended, which prompts questions from the business. It's our job to make sure that the total billed amount is correct, and this post discusses this in the context of our old friend the TLM (Transmission Loss Multiplier). In a previous post I discussed the forthcoming RAB charge, which is billed at NBP kWh. Some other pass-through charges calculated at NBP kW are:

I talked before about how to calculate NBP kWh, but let's now dive deeper into TLMs. I'm a programmer working on Chellow, and here's a screenshot of the TLMs file being downloaded into its database:

TLMs being downloaded into Chellow

You can see the URL of the TLM file, with my scripting key blurred out. It's free to register for the Elexon Portal and then you get a scripting key that's unique to you. Here's what the TLM file looks like:

TLM Spreadsheet

The Settlement Date and Settlement Period tell you the half-hour that the TLM is for, the Zone maps to the GSP Group and the bit we're going to focus on is the Settlement Run Type. The run is the version of the data, with later runs being issued as the data becomes more accurate. The runs are:

II
1 Week
SF
1 Month
R1
2 Months
R2
4 Months
R3
7 Months
RF
14 Months
DF
28 Months

So for example if a TLM is labelled SF, it means that it was issued one month after the date that the TLM was for. You can see where the reconciliations come from now. Say the supplier produced the first bill before SF, then when SF occurs the charges passed through to the Supplier may have changed, and they may change again in the future, which can result in the supplier issuing reconciliations to the customer.

Where does that leave us as bill validators? Firstly we need to be able to model this, so that as soon as a new run comes out we should tell the business the impact this will have on the bills and include it in the accrual. Then, when a reconciliation arrives we need to check that it's accurate. Also, we need to chase things up with the supplier if an expected reconciliation doesn't arrive, especially if it's in our favour 🤑

Finally, in checking the bills, we need to know which settlement run the supplier used to produce the bill. Unfortunately, in my experience, suppliers aren't good at doing this, but I'd be interested to know what your experience is.

See you next time! ✨