Blog

Chellow and general energy billing news. Get in touch if you'd like to write a blog post.

Getting a Connection Agreement Document

Last week I ran a bill check on the latest batch of bills from a supplier, and the DUoS availability charge was flagged up as a problem: You can see that in the actual bill from the supplier, the siz…Continue Reading

2026-05-04

Elexon TLM File Glitch?

On Thursday last week I saw a message on Chellow alerting me to a problem with the automatic imports from Elexon: There were two problems: The date format had changed. There were extra Transmission …Continue Reading

2026-04-25

VTP Pass-through Charge

The Virtual Trading Party (VTP) pass-through charge came to my attention this week, with the prospect of it appearing in the next batch of bills that we receive. I'm still trying to understand the det…Continue Reading

2026-04-18

Market Roles Of A Data Collector

The other day I ran what we call our Chellow vs ECOES report, which creates a list of discrepancies between the characteristics of supplies held in Chellow and their characteristics in the industry da…Continue Reading

2026-04-06

LAFs From Industry Standing Data

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 h…Continue Reading

2026-03-28

Issue Tracking

As you go about validating energy bills, you come across various problems you want to log and then go through ticking them off when they're resolved. It's nice to have a convenient list to send off to…Continue Reading

2026-03-22

Electricity Accruals

I expect that many of you, like me, will be involved with producing the electricity accrual each month for Finance. The accrual is the cost of electricity that's been used, but not yet billed. For Fin…Continue Reading

2026-03-14

Associated MPANs

A large site will often have multiple electricity supplies, each with their own MPAN. However, the connection agreement with the DNO will group the MPANs together for charging certain elements. These …Continue Reading

2026-03-08

ECOES

In the previous post I wrote that each supply has an LLFC, or to be more precise, each MPAN has an LLFC, one for import and one for export if the supply has an export MPAN. The electricity industry vi…Continue Reading

2025-11-29

LLFCs

In the previous post I mentioned that every electricity supply has a Line Loss Factor Class (LLFC), which is a 3 character code that reflects the supply's characteristics. Here's a screenshot from Che…Continue Reading

2025-11-22

Calculating GSP kWh

We've finished a run of posts on calculating kWh at NBP. As a reminder, electricity travels through the transmission system, then through the distribution system and then ends up being measured at the…Continue Reading

2025-11-15

Forecasting NBP kWh

We've had a run of NBP kWh related posts ( Calculating NBP and NBP Reconciliations, and this post rounds off the series by talking about forecasting NBP kWh. Even though actual TLMs are specific to th…Continue Reading

2025-11-08

Reconciliations and NBP kWh

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 …Continue Reading

2025-11-01

Calculating kWh at NBP

Before we get into NBP kWh, there's an update on the previous post on finding DNO tariffs. I've heard from the industry body DCUSA that they're working on an API for DNO tariffs, which is great news. …Continue Reading

2025-10-25

Finding DNO Tariffs

In a pass-through electricity contract, one of the things that is often passed through are the Distribution Use of System (DUoS) charges from the Distribution Network Operators (DNOs. The DNOs publish…Continue Reading

2025-10-18

Forecasting RAB costs appearing in December

The RAB charge is a subsidy for nuclear generation that will appear as a separate item in bills for those with a pass-through contract. The first RAB charges will appear in bills for December's consum…Continue Reading

2025-10-11

Element-Level Billing

An electricity bill is made up of many individual elements, each with a cost attached to them. Some examples of elements are: ccl (Climate change levy) eii (Energy intensive industry support payments…Continue Reading

2025-10-09

Recent changes to Chellow

Here are some notes on recent changes to Chellow: We've begun to address the vexed question of clock-time and UTC. Clock-time is what UK clocks say the time is, and it would seem obvious that this is…Continue Reading

2020-01-04

Missing Bill Elements That Aren't Missing

TL;DR The bill check no longer says that bills are missing when they're not. A Chellow user (we'll call them Jem) said to me, 'When I run the bill check it says that some bills are missing when they a…Continue Reading

2019-11-09

Introduction

Chellow is an open source web application for checking UK electricity and gas bills for large organisations. It's been used in production since early 2006, and so it's about time it had its own websit…Continue Reading

2019-08-26