High-Efficiency Condensing and Non-Condensing Gas Tankless Water Heaters

Condensing tankless water heaters are more efficient than non-condensing models. Condensing units capture and reuse exhaust heat, achieving efficiency ratings up to 0.95 UEF. Non-condensing models vent excess heat away rather than capturing it for reuse, typically achieving 0.82 UEF. While condensing models cost more upfront and require condensate drainage, they deliver greater energy savings over time.

How do I keep my tankless water heater from freezing?
All A. O. Smith tankless hot water heaters have built-in freeze protection. However, if the heater is installed outdoors, during a power outage you will need to drain the water from the unit to prevent freezing.

Does a non-condensing tankless water heater require a drip pan?
Use a drip pan with your tankless water heater as a precaution. This protects your home from water damage and mold should the water heater leak. Because tankless models don't have storage tanks, a drain pan should be enough to contain any leakage.

Non-condensing tankless water heaters require metal exhaust venting to handle higher temperature exhaust gases. Concentric models use a metal inner pipe with a plastic outer pipe, combining intake and exhaust in a single unit. These units vent excess heat directly outside rather than capturing it for reuse, resulting in hotter exhaust that needs durable metal piping. Outdoor models have built-in vents that eliminate the need for venting through walls. Your installer will determine the proper venting configuration based on your home's layout and local building codes.

No, only condensing tankless water heaters produce condensate that requires drainage. Condensing models capture and cool exhaust gases, which creates moisture that must drain away. Non-condensing tankless water heaters vent hot exhaust gases directly outside at higher temperatures, so no condensate forms and no drain line is needed. However, a drip pan is still recommended as a precaution against potential leaks.