Rinnai.

The company’s new condensing tankless water heaters offer the continuous hot water of a traditional tankless unit with even greater energy savings: The Energy Star–qualified units operate at 95% thermal efficiency, according to the company. The water heaters feature two commercial-grade heat exchangers; a concentric venting design provides for better safety and easier installation. Four models are available. 866.746.6241. http://www.rinnai.us/.