Navien Tankless Sizing

In this section, the sizing of Navien units is simplified for you. If you wish to see the math behind these calculations, see the section entitled "The Math of BTUs and Tankless Sizing" on the "Learning Center" page section of the Navien website.

Many tank-type water heater manufacturers have simplified the sizing of tanks to the number of people living in the home or to the total number of fixtures. Sizing a Navien tankless water heater is different. Navien units are sized to meet the number of fixtures that a home owner expects (or wants the capability) to run simultaneously. Because of the varying ground water temperatures across North America and across seasons, the flow rates will change depending on the region you live, but typically, Navien tankless units can typically provide either 2 or 3 major fixtures simultaneously without problem even on the coldest of winter days.

Cold Weather Climate Residential Rule of Thumb Sizing Chart

If you live in an area identified in red in the map below, please use the cold weather scenarios to select your water heater.

Examples of Typical Cold Weather Residential Scenarios

1) Light Residential Volume in Cold Weather Areas:

If 2 people are living in a bungalow style home that only has one shower, a Navien CR-180(A) (our smallest unit) may be the perfect solution. Given that there are only two people living in the home, using more than 1 hot water fixture at any one time would probably not occur very often. If it was occurring, adjusting schedules to ensure fixtures are run consecutively may not result in any major change in lifestyle pattern (i.e. starting the dishwasher only after a shower is finished rather than at the same time, in most cases, should not result in any significant inconvenience).

2) Standard Residential Volume in Cold Weather Areas:

If there are 5 people living in a home (for example, 2 parents that both work 9~5 and 3 teenagers), having 2 showers (or 1 shower and the kitchen sink, etc.) running simultaneously on a daily basis is highly likely, especially in the morning when everyone will be trying to get to work or school at similar times. For this type of family, the CR-210(A) or CR-240(A) would be the recommended units.

3) Heavy Residential Volume in Cold Weather Areas: For heavy volume, multiple units will be required. A typical scenario would be if there are 3 or more showers in a home that expect to be used simultaneously, or if you have a high volume body spray shower system requiring more that 4 GPM of hot water. In addition, multiple units will speed the fill time on large volume whirlpool or soaker tubs. For this type of family, multiple CR-240(A) units would be recommended.

End User Expectations for Cold Weather Areas

The CR-180(A) can provide enough volume to supply 1 shower and 1 lavatory basin simultaneously in the worst of winter weather. To simplify sizing, Navien America typically advises that the CR-180(A) can do 1 fixture at any one time. For those end-users that expect to use hot water fixtures consecutively (one after the other; no simultaneously usage), the CR-180(A) is the perfect unit. Please do not expect the CR-180(A) to supply 2 or more major fixtures simultaneously.

For those who need even more, the Navien CR-240(A) is capable of supplying 3 showers worth of water simultaneously or when multiple CR-240 units are manifolded together as a system, Navien can supply as much volume as you need to run any application. Please see the commercial sizing section below for sizing suggestions.

Residential Sizing Determination Tip Before Making a Purchase

To determine how many fixtures are in use simultaneously, suggest to the end-user that over the next few days, each time they turn on a hot water fixture, make a mental note of how many other fixtures are on at exactly the same time. If most of the time, there are no other fixtures running, the CR-180(A) would be ideal. However, if they find that much of the time 2 fixtures are running simultaneously, then the CR-180 (A) would not be enough for that household and it would be recommended to step up to a larger model such as the CR-210(A) or CR-240(A).

If you prefer to size based on GPM rather than fixtures, the Navien units will produce between 3 ~ 8.7 gallons per minute (GPM) depending on the model as outlined in the chart below (based on a cold water supply of 40˚F and the unit output set at 120˚F which would be standard design for cold weather areas):

For ground water temperatures other than standard design, please see the follow chart for corresponding delivery capability: