Water heaters provide hot water for homes and other buildings. Electric water heaters have screw-type immersion elements and over-temperature protectors that provide automatic shutoff. Gas water heaters are typically installed in areas where electricity is more expensive than liquid propane (LP) or natural gas. Tankless water heaters provide hot water on demand. Since they are not constantly heating and reheating water in a tank, they are more efficient than water heaters with a storage tank.