Tankless Water Heaters

Tankless water heaters heat water only when a tap opens, so there is no storage tank to keep hot and no 40- or 50-gallon limit on a long shower. This collection brings together every complete tankless unit we carry, gas, propane and electric, from Navien, Rheem, Noritz, Stiebel Eltron, Intellihot and IBC. Valve kits, vent pipe and repair parts are listed separately.

Gas, propane or electric

Natural gas units deliver the most hot water for the fuel cost and run from 120,000 to 199,900 Btu/h for whole-house use. Propane models are built for LP and suit homes off the gas main, and many Navien and Rheem IKONIC units are field-convertible between the two fuels. Electric tankless heaters need no vent or gas line, but an 18 to 36 kW whole-house unit draws roughly 75 to 150 amps, so check your electrical panel first. Small point-of-use models serve a single sink.

Condensing or non-condensing

Condensing units reach 0.93 to 0.96 UEF by recovering heat from the exhaust, so they vent through PVC, CPVC or polypropylene and need a condensate drain with a neutralizer. Non-condensing units cost less up front but need stainless steel Category III venting. Outdoor models skip indoor venting altogether.

Sizing in GPM

Size a tankless heater by flow rate, not by gallons. Add up the gallons per minute (GPM) of the fixtures that run at the same time, then check each unit's flow at your winter temperature rise. A 199,900 Btu/h gas unit gives about 5 GPM at a 70°F rise, enough for two showers at once in most of the country. Colder groundwater means less flow from the same heater. Our guide on what size tankless water heater you need walks through the math.

Shop by type or brand: gas tankless water heaters, electric tankless water heaters, propane tankless water heaters, Navien and Rheem. For the install, add tankless valve kits.

Comparing with a tank? See Rheem 40 gallon and Rheem 50 gallon water heaters, or heat pump water heaters. Need heating and hot water from one unit? See Navien combi boilers.