One step in the right direction is the inclusion of five categories of water heaters in the Energy Star program: high-performance gas storage, whole-home gas tankless, advanced drop-in or integrated heat pump, solar, and gas condensing. For more details on the requirements for each categories, you can see this Energy Star announcement.
GE hasn't wasted any time announcing two new models that will meet the new Energy Star criteria. The first one is a tankless (aka on-demand) gas water heater that should "save up to 25 percent annually on water heating costs compared to the operating costs of a standard 40-gallon gas tank water heater." The second model is more intriguing. It is a hybrid electric water heater (pictured below) that promises to use half as much energy as a traditional model yet use the same footprint and connections.
It kinds of look like something you would see in a science fiction video game.
The hybrid part works by combining conventional electric heating with a heat-exchanger that absorbs heat from the room to help warm the water. This is a good thing when your house requires cooling, but not when heating is required, so we expect these to make more sense in the warmer regions of the globe.
The hybrid should be available in late 2009, while the Energy Star GE gas tankless will be available May 1, 2008.
::U.S. Department of Energy Implements Criteria for ENERGY STAR® Water Heaters, ::GE® first to announce water heaters that will meet new DOE ENERGY STAR® standards, via ::GE's New Water Heater Could Kill 30 Coal Plants