Since I arrived in Mexico City a couple months ago, I have observed many new and old homes with strange contraptions on the roof. At first I thought they were skylights, but then I realized that they are in fact solar water heaters. This seemed like a great idea, especially for places that get a lot of sun. Not only are they economical, but they also help to save resources. After doing a little research, I learned that heating water is the second largest energy consumer in the average American home, so a more efficient system would mean great savings in energy costs.