The ZigBee Smart Energy system offers core technology for monitoring, controlling, and automating the delivery and use of energy and water.
Overall, the ZigBee system is a home automation and monitoring network. It is a data network specifically purposed for home automation purposes. "The goal of the ZigBee Alliance is to provide the consumer with ultimate flexibility, mobility, and ease of use by building wireless intelligence and capabilities into everyday devices. ZigBee technology will be embedded in a wide range of products and applications across consumer, commercial, industrial and government markets worldwide. For the first time, companies will have a standards-based wireless platform optimized for the unique needs of remote monitoring and control applications, including simplicity, reliability, low-cost and low-power."
This image may make the role of this technology a little clearer. It facilitates collecting information about energy use within a home setting, a corporate setting, and may facilitate sending information to a utility or retrieving information from a utility. For example if utility companies were to send out real time pricing information, the customer devices could make real time decisions about which gizmos to turn on or off.
The Z-Aperture™ products from Alektrona interface a ZigBee network to the Internet. That allows one to write or acquire software packages running on the Internet (e.g. a home WiFi system) and interact with or monitor ZigBee devices on a home network.
The Landis + Gyr Focus AX endpoint is an advanced metering endpoint that provides two-way communication with the utility, meter and home-area networks. I tried going to their website but didn't find the specific product page. It's clear that they provide utility grade power meters such as the one on your house, and having a smarter utility meter is important for the pictured scenario above with data exchange to/from the utility companies.