Unidentified Gas (UIG)

It’s difficult to forecast UIG with great certainty because as the ‘balancing figure’ each day, UIG can be influenced by many different factors including:

• Accuracy of Total Local Distribution Zone (LDZ) Energy forecasts/measurements/stock change
• Accuracy of DM Energy forecasts/measurements
• Accuracy of Non-Daily Metered (NDM) Demand forecast which can be impacted by:
  • Annual Quantity (AQ) accuracy
  • Unexpected reactions to weather by Non-Daily Metered (NDM) sites
  • NDM sites in an inappropriate End-User Category (EUC) (e.g. not in a WAR Band EUC)
  • Imperfections in the NDM demand models or supporting sample data
  • Accuracy of forecast/actual weather data
• Levels of incorrect theft in the LDZ
• Missing sites in the LDZ, e.g. shipperless or unregistered sites

All these influencing factors can mean that at D+5 Exit Close-Out, UIG may be negative. UIG will subsequently be subject to Reconciliation, as individual Meter Point Reconciliations occur.

Note: D+5 = the fifth day after the end of the Gas Day which is when Daily Allocations are finalised (Exit Close-Out in Uniform Network Code terminology).

UIG only applies to Local Distribution Zone (LDZ) sites.

Non-Standard sites on Local Distribution Zones (LDZs) will be allocated a Class and End-User Category (EUC) based on site attributes and will attract the appropriate UIG Weighting, based on the prevailing set of Weighting Factors.

The Registered System User’s (RSU) total system outputs include their share of Local Distribution Zone (LDZ) UIG.

The RSU will not be billed for their UIG allocation on the Network. They will only be billed for any excess or shortfall in the gas that they have delivered to the total System compared to total outputs. This is a System-wide calculation, not LDZ by LDZ.

This means that the RSU share of UIG will not appear on any invoice. Instead, it will be just another input to the existing Energy Balancing process. As UIG meters are part of the overall daily imbalance (they are within the allocated outputs of your overall daily imbalance) - timings, prices etc are unchanged.

As stated above, UIG is not cashed out or billed separately. Imbalances prior to D+5 are not chargeable – it’s only the D+5 closed-out position that feeds into Energy Balancing. The overall daily imbalance is cashed out at the relevant System Marginal Price (SMP).

There are no Scheduling Charges on UIG or Non-Daily Metered (NDM) allocations, so no penalty or incentive to buy the exact quantity as per the Nominations.

This is explained further in our Unidentified Gas Education Pack.

Unidentified Gas (UIG) can be re-calculated up to four times a day for the day ahead (‘D-1’) and up to five times within-day (for ‘D’) whenever there has been a change to a Daily Metered (DM) Nomination or the forecast Composite Weather Variable (CWV).

Unidentified Gas (UIG) could be negative for one or more Local Distribution Zones (LDZs) for any given Gas Day. This is not necessarily an error, as UIG at D+5 is only an interim accounting position and subject to further reconciliation.

Where negative UIG occurs for a number of LDZs this is likely to be as a result of NDM modelling error e.g. where the estimate of NDM demand is too high for the day meaning UIG goes negative (as the balancing figure). The NDM Modelling Error presentation provides more detail.

From March 2022 to the end of summer 2023, the industry saw an extended period of negative UIG across all LDZs. This was due to the unprecedented drop in consumption as a result of the energy crisis, which resulted in the NDM Algorithm significantly over allocating the NDM population.

We hosted a webinar to explore this further – please view the presentation to find out more.

Meter Reads are used to reconcile the consumption of each individual Meter Point, with the System Average Price (SAP) rates used to calculate the monetary value.

Note: The System Average Price (SAP) can be found on National Gas Transmission’s data portal. 

The equal and opposite amount of all individual reconciliations’ energy (and monetary value) amends the Unidentified Gas (UIG) position. Those Reconciliations appear on the monthly Amendment Invoice.

UIG Reconciliation is shared out based on the latest (reconciled) allocations or measurements for the last 12 billing months, using the applicable UIG Weighting Factors.

Meter point reconciliation, both Daily Metered and Non-Daily Metered, can be processed back to the Line in the Sand (i.e. 1 April minus three years).

Depending on the accuracy of the original measurements and estimates used in Allocation, UIG Reconciliation may be a debit (charge) or credit (refund).

It takes many months or years for all meters to be read and trigger reconciliations. As of March 2022, there are over 170,000 sites which have not had a meter reading since the current “Line in the Sand” (the Code cut-off Date of 1 April 2019), so there is still scope for further Reconciliation movements.

This means that the monthly positions will keep changing and may switch between debit and credit over time.

The net charge for UIG Reconciliation each month reflects the equal and opposite of the net effect of all the primary Meter Point Reconciliation processed each month.

However, all the meter point reconciliations back to that date for a month are summed up, and all charged/credited to UIG. There is no gain or loss of energy in the process.

The sum of all the meter point reconciliations is divided by 12 and shared back across 12 months of weighted throughput.

 The Unidentified Gas (UIG) smear is calculated as a flat smear across all the qualifying months, rather than being smeared back to the months of the underlying transactions, which could be longer or shorter.

For example, if the primary Rec quantities in a Local Distribution Zone (LDZ) totalled 12m kWh debit:

• Monthly UIG smear: +12m kWh / 12 = 1m kWh credit per month.
  
  

The monthly UIG would be shared out in line with the latest weighted throughputs.

There are two online screens and one Application Programming Interface (API) through which Shippers can view both Forecast and Allocation Unidentified Gas (UIG) Quantities.

Screens

Shipper Forecast UIG Report

Shipper Allocation UIG Share Report 

API
View Shipper UIG Values

Currently, total Unidentified Gas (UIG) is not visible on Shipper screens (Shippers only see their own share) however, it can be viewed on a spreadsheet (both energy and %).

You can access this spreadsheet in UK Link Secured Documentation *

(Then 18. NDM Profiling and Capacity Estimation Algorithms/Demand Estimation Project Nexus/LDZ UIG Values)

*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

Following the launch of a new industry settlement regime in June 2017, Unidentified Gas (UIG) became (and remains) a priority issue for the gas industry. In our role as the Central Data Service Provider (CDSP), we created a UIG Task Force that was responsible for investigating and making recommendations on how to reduce UIG levels and volatility.

Between 2018 and 2020, our Task Force worked with an analytics provider to:

1. Investigate and report on the causes of UIG
2. Suggest how the level and volatility of UIG could be reduced

We summarised the output from the Task Force in this closedown report, which is available on the Joint Office of Gas Transporters’ website.

You can find more detailed information on the UIG Task Force in our UK Link Docs secure area.

(Folder 18.NDM Profiling and Capacity Estimation Algorithms / UIG / UIG Task Force)