Water heaters can account for a significant portion of your home's energy usage. According to the U.S. Department of Energy, water heaters are the second largest energy consumer in most residential households, after space heating and cooling. There are a number of factors that affect how much energy a water heater uses, including the type of water heater, the size of the unit, the efficiency of the unit, and how often it is used. Electric water heaters are typically the most energy-efficient option, followed by gas water heaters. Tankless water heaters are also a more efficient option than traditional storage tank water heaters. If you're concerned about your home's energy usage, you can install a low-flow showerhead, which will reduce the amount of water you use without sacrificing water pressure. You can also insulate your water heater and pipes to help keep heat in and reduce energy loss. And, if you're in the market for a new water heater, be sure to choose an ENERGY STAR certified model, which can save you money on your energy bills.