CMOS Parameter Group

This CMOS Parameters working group has been established as a working group of the Strategic Panel to assess and review the following Central Systems (CMOS) parameters:

• ILEs: these are estimates of average water usage, grouped by meter size, used for estimation purposes. They are often referred to as ‘backstop’ estimates, as they are only used to estimate volumes for meters which have no specified Yearly Volume Estimates (YVEs).
• VECs: these are caps used in the volume estimation process, for a period after a meter’s latest read, and limit the effects of inaccurate meter reads on volume estimation by setting upper volume limits. There are two caps: the Icap with a value of 10, and the Ycap with a value of 3. The Icap is applied where ILEs are used for volume estimation, whilst the Ycap is applied where YVEs are used for volume estimation.
• RDA: this is an algorithm that determines, based on a meter’s historic reads, whether a read submitted is a rollover or not. In cases where it cannot make a determination, CMOS relies upon the trading party’s indication.
• NMDC: this outlines typical measuring limits for meters, above which measurement of water is likely to be inaccurate. The limits are grouped by meter size
• YVEs are non-negative integer estimates of the annual volume supplied to occupied premises, in cubic meters, initially provided by the Wholesaler and thereafter maintained by the retailer.