Your audit should include locating and evaluating your water heater. In many homes, the water heater is the second largest energy user, so it's worth taking some time to investigate. Check its temperature setting. Keeping it as low as possible will save energy and money. Place your hand on the tank to see if is warm to the touch. If it is, it may be a candidate for an insulating blanket, especially if it is located in unconditioned space.