Ever wonder why the last digit of your National Grid account number changes every so often?  The last two digits of the twelve digit number referenced under "Account Number" on your National Grid bill are referred to as the "Tenant Number"...originally developed by the utility to keep track of changing tenant account ownership in rental properties.  Every time a change in account ownership transpires, the last digit of the tenant number increases by one.  Technically speaking, this is not a change in your account number [which is really the first ten digits]...just an increase in the tenant number.

With the onset of energy deregulation, the same phenomenon occurs every time your utility account changes supplier service [i.e. switching from the utility supplier service to a competitive supplier, or switching from one competitive supplier to another, etc].  The utility's current billing system has no way of tracking changes in supplier, so the utility uses the tenant number to do this.  SilentSherpa has been told by National Grid that this digit change will go away with the roll-out of their new billing system in late 2007.