Stiebel Eltron Tempra Plus whole-house tankless electric water heaters are 99% efficient and feature advanced flow control to automatically keep output temperature consistent, while supplying a continuous hot-water flow. Stiebel Eltron notes the heaters provide a minimum of 15% to 20% energy and water savings, and includes a three-year warranty. At a space-saving 17” by 15” by 5”, the Tempra Plus is easily installed with no venting. Tempra Plus units are ideal backups for solar-thermal systems.