Real_time Price Message Line 525 spec wd-08

[ed@cazalet.com]

Initial thoughts on defining real-time price messages at line 527 of draft spec wd-08. - Ed Cazalet 3-16-10
We have defined real-time price as a price for any amount of energy.  Forward prices and forward transactions are also to be defined, but this note focuses only on real-time price and transactions.
Real time prices can be defined for any interval of time.  60 minutes, 15 minutes, and 5 minutes are typical interval lengths for real-time prices. However, as technology improves, real-time intervals can be the shortest interval that can be read by a meter.  For example, I have been told that the meters now being installed by PG&E will provide readings on six second intervals over the home area network, but intervals of 15 min will be typical for backhaul to the utility.
A real-time price is typically ex-ante or ex-post.  An ex-ante price is a price quoted to the customer before the real-time interval. An ex-post price is a price known to the customer after the interval is passed.  An ex-post price has the advantage to the supplier in that she will know amount purchased before a price is set.  An ex-ante price quote has the advantage to the customer that she will know the price before deciding how much to buy.
In fact both ex-ante and ex-post prices can be used.  In this case the a quantity is transacted at the ex-ante price and any difference between the meter quantity and the transacted quantity is priced at the ex-post price.