In addition to ensuring the highest efficiency levels, Rheem gas water heaters are also durable and energy-efficient. These water heaters are made with a bowl-shaped tank, ensuring that water drains out straight. Additionally, non-metallic tanks minimize the chance of rusting, and titanium elements replace the anode rods. Despite the brand's reputation for quality and durability, consumers have few complaints about their water heaters. The Tempra tankless model from Stiebel Eltron boasts patented Advanced Flow Control technology, which allows for even heating when water flow varies. This feature helps the tankless water heater keep the water at a steady temperature even if there is a sudden rise in demand. Similarly, tankless electric water heaters from other manufacturers do not respond to fluctuations in demand and may cause sudden cold showers.