A power consortium that distributes a mix of "green" and conventional electricity is implementing an XML-based settlements system that drives costs out of power distribution.

The Northern California Power Agency is one of several state-chartered coordinators in California that schedules the delivery of power to the California power grid then settles the payment due the supplier. NCPA sells the power generated by the cities of Palo Alto and Santa Clara, as well as hydro and geothermal sources farther north.

Power settlements are a highly regulated and complicated process. Each settlement statement, which can be 100 Mbytes of data, contains how much power a particular supplier delivered and how much was used by commercial vs. residential customers. The two have different rates of payment, set by the Public Utilities Commission.

The settlements are complicated by the fact that electricity meters are read only once every 90 days; many settlements must be based on an estimate of consumption that gets revised as meter readings come in.

On top of that, there are fees for transmission across the grid, sometimes set by the PUC to apply retroactively. On behalf of a supplier, NCPA can protest that fees for transmission usage weren't calculated correctly, and the dispute requires a review of all relevant data.

Getting one or more of these factors wrong is a commonplace. "Power settlements are never completely settled," said Bob Caracristi, manager of power settlements for NCPA, in an interview. Negotiations over details may still be going on a year or two after the power has been delivered.

Furthermore, "the enormity of the data" has in the past required a specialist vendor that creates software to analyze the massive settlement statements produced by the grid's manager, the California Independent System Operator.

NCPA sought these vendor bids three years ago and received quotes that were "several hundred thousand dollars a year in licensing fees and ongoing maintenance," said Caracristi. The need for services from these customized systems adds to the cost of power consumption for every California consumer.

Faced with such a large annual expense, NCPA sought instead to develop the in-house expertise to deal with the statements. Senior programmer analyst Carlo Tiu and his team at NCPA used Oracle's XML handling capabilities gained in the second release of 10g, a feature known as Oracle XML DB. They developed an XML schema that allowed Oracle to handle the data and an XML configuration file that contained the rules for determining supplier payment from the data. That file can be regularly updated, without needing to modify the XML data itself.

In addition, his team created a file that contained the scripts for configuring Oracle to handle the XML schema and data.