A British developer, Qreative Medias, has introduced a Home Energy Performance application that works on iPhones and iPads. The idea is that you can either rate your own property OR check out the energy profile of a home you might be thinking about buying. The application cooks up several different types of energy efficiency scores, appropriate for the United States, the United Kingdom or Europe. In the United States, the software uses recommendations from the Environmental Protection Agency's Energy Star program and the U.S. Department of Energy Building America initiative.
So far, the application (which costs $3.99 to download) is available in English, French and Spanish.
Just for grins, I did a quick search on the Apple store to see how many other applications of a similar sort come up if you look for home energy management applications. There are easily 30 of them that have some sort of energy connection, such as a solar panel installation guide ($4.99) from New Jersey Solar Consulting to simple green guides and tips that are either free or pretty inexpensive (99 cents) to a $99 application (yes, $99!) from Mobile Integrated Solutions that is designed to let you manage the intelligent energy controllers throughout your home via your iPhone.
Out of curiosity, I also ran a search on the Appolicous store for Android applications that is run in concert with Yahoo! Although they are harder to find, there are some there, including a free energy savings calculator that lets you figure out cost reductions you might find related to inefficient appliances and lightbulbs.