Out of all the appliances in your home the water heater can be using most of your energy. According to the Department of Energy the water heater uses on average 17% of an American households energy. Typically, an electric hot water heater uses $438 worth of energy a year compared to a gas water heater which is around $224. Gas is usually cheaper but it is still a fossil fuel and cannot be supported by a solar system. Tankless water heaters are usually 20%-30% more efficient as well. Some keys to keeping your water heater bill down is to turn the thermostat down to 120 degrees, take quick showers/turn the water off while soaping up, install low flow water heads, insulate your tank, upgrade to a more efficient model, and be conscious at all times with how water is being used.