Ranking Criteria: The most efficient water heaters, ranked by Energy Factor, based on likely annual energy consumption. ENERGY STAR also uses this calculation.
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#1

Eternal
GU145(S)

This is a medium-sized gas-condensing tankless water heater.

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#1

Navien America
NP-180, NR-180

This is a medium-sized gas-condensing tankless water heater.

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#2

Navien America
NP-180A, NR-180A

This is a medium-sized gas-condensing tankless water heater.

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#3

Rinnai
RC80HPe, RC80HPi

This is a medium-sized gas-condensing tankless water heater.

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#4

Quietside
ODW-120A

This is a medium-sized gas-condensing tankless water heater.

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Category Last Modified: September 15, 2011