Choosing the Best Natural Gas Tankless Hot Water Heater: Featuring 3 Models With Distinct BTU Outputs

The Verdict, and the Basis for It

The Rinnai V75IN Tankless Hot Water Heater is the best Natural Gas Tankless Hot Water Heater because it delivers a high 7.5 GPM flow rate for heavy-duty household use.

Choosing a tankless system often feels overwhelming because the difference between a unit that handles a full bath and one that runs out of hot water mid-shower is significant. Selecting the wrong model can lead to cold water during peak usage times when multiple fixtures are active.

The Rinnai V75IN Tankless Hot Water Heater provides the high-volume flow needed for large households, while the Noritz NRC66DVNG serves those needing a high-efficiency condensing model and the CAMPLUX unit suits users seeking a budget-friendly copper-tank design. We evaluated the tankless water heater installation options we track against this topic’s criteria at Green Writer.

The prices for these selections range from $489.99 to $1091.16, with a median price of $629.99 across the 7 products in our comparison.

Full Comparison Table

Prices are approximate and move frequently – check the current price before deciding. “Not stated” means the manufacturer listing does not give that figure – we do not estimate it.

The Rinnai V75IN offers the strongest price-to-spec ratio because it provides the highest 7.5 GPM flow rate among the high-capacity options.

Each Pick, Reviewed

The 3 picks below run from $489.99 to $1091.16, reviewed in rank order.

Rinnai V75IN Tankless Hot Water Heater

The Rinnai V75IN made this list because it provides a high-volume flow rate and a 10-year residential factory warranty on the heat exchanger, making it a reliable choice for natural gas users needing consistent performance.

What we like: The Rinnai V75IN delivers a flow rate of up to 7.5 GPM, which exceeds the 3.5 GPM threshold required for a standard shower head. It also supports up to 5 appliances at once and carries a 4.4 rating from 2,812 buyers.

Keep in mind: This unit is intended for indoor installation and requires a professional installer to ensure the gas lines and venting meet local safety codes.

Noritz NRC66DVNG Indoor Condensing Tankless Hot Water Heater

We selected the Noritz NRC66DVNG for its high-efficiency condensing technology and its position as a more budget-friendly option for natural gas systems.

What we like: This model offers a 6.6 GPM flow rate and includes a remote thermostat and a 6-foot power cord. It features a 4.3 rating and is priced at approximately $489.99.

Keep in mind: The 6.6 GPM flow rate may be insufficient if you need to run two showers and a sink simultaneously, which typically requires a 10 GPM threshold.

CAMPLUX Natural Gas Tankless Hot Water Heater

The CAMPLUX unit is included for its compact design and its ability to provide hot water to multiple points like the laundry room and kitchen simultaneously.

What we like: This unit features a pure copper water tank and a BLDC variable-speed fan. It provides a 5.28 GPM flow rate and is priced at around $629.99.

Keep in mind: With a 5.28 GPM flow rate, this model is best suited for smaller households or those with 2-3 water points rather than high-demand multi-bathroom setups.

How many gallons per minute (GPM) do I actually need for my household?

The GPM you need depends on how many fixtures you run at once. You need at least 3.5 GPM for a standard shower head, but you should aim for 10 GPM if you need to run two showers and a sink simultaneously without a drop in temperature.

How much clearance do I need around the unit for local building codes?

Clearance requirements vary by municipality and the specific model’s venting needs. You must confirm the required clearance for your specific model and local codes with a qualified installer before purchasing, as many units cannot be placed in tight spaces due to safety spacing requirements.

You might also compare various tankless water heater alternatives to see if a different system fits your needs.

What Separates One Tankless Water Heater Installation From the Next

Maximum Flow Rate In GPM

Prioritize a flow rate that matches your household’s peak demand, such as the 3.5 GPM required for a standard shower or 10 GPM for simultaneous use across multiple fixtures. The Rinnai V75IN provides the highest flow rate among the options we compared at 7.5 GPM. For smaller spaces, the CAMPLUX offers 5.28 GPM, which supports 2-3 water points at once. If you need to run a shower and a sink simultaneously without a drop in temperature, look for units exceeding 6 GPM.

BTU Input Capacity

BTU input capacity determines the unit’s ability to heat water quickly in cold climates; a low BTU deficit can prevent a unit from reaching the desired temperature. While the specific BTU values for these models vary by climate rating, the Rinnai V75IN is designed for high-volume output. Ensure the unit’s BTU rating meets the requirements for your local climate and the number of fixtures you intend to run at once. Consult the manufacturer’s technical sheet to confirm the BTU output matches your specific hot water demands.

Condensing Vs Non-Condensing

Choose a condensing unit if you want higher energy efficiency, but be aware that condensing models like the Noritz NRC66DVNG require specific Schedule 40 PVC venting. Non-condensing units are often less complex to vent but may have higher monthly gas costs. The Noritz NRC66DVNG features high-efficiency condensing technology, while the Rinnai and CAMPLUX serve as standard high-performance options. Weigh the higher upfront cost of a condensing model against your long-term monthly gas bill savings before choosing.

Fuel Line Pressure Requirements

Fuel line pressure requirements dictate the necessary gas supply to the unit to maintain a consistent flow rate. Because these are natural gas models, you must confirm your home’s gas pressure meets the specific requirements for the Rinnai, Noritz, or CAMPLUX models before purchase. If your gas pressure is insufficient, the unit may fail to provide the rated GPM. A qualified installer must verify your gas line’s pressure and diameter to ensure the heater receives the necessary fuel volume.

To better understand the technical details, view our guide to tankless water heater specs explained in plain English.

What You Need vs What These Picks Deliver

Match the job you actually need done to what it requires, then check whether anything on this page reaches that level. Where nothing does, the row says so.

Thresholds are the levels this category is generally held to, not manufacturer claims. Check them against your own workload before buying.

Who Buys Tankless Water Heater Installations, and What It Really Costs

Questions Buyers Ask Before Choosing

How much BTU capacity does my gas line need?

Your existing gas line must provide sufficient BTU capacity to power the specific tankless unit you select. Because these units heat water on demand using high-intensity burners, you should consult a qualified installer to measure your home’s piping and confirm it meets the requirements for a high-flow system.

What is the expected lifespan and warranty for these units?

The Rinnai V75IN provides a 10-year residential factory warranty on the heat exchanger and a 5-year warranty on labor. For other models like the Noritz NRC66DVNG or the CAMPLUX unit, you must verify the specific manufacturer’s warranty terms at the time of purchase as these vary by model.

Which model should I choose for high-volume flow?

If you require the highest flow rate, the Rinnai V75IN provides a 7.5 GPM output, which is the highest among the options we evaluated. The Noritz NRC66DVNG follows with a 6.6 GPM flow rate, while the CAMPLUX offers 5.28 GPM.

Is the CAMPLUX model worth it for a smaller home?

The CAMPLUX is a practical choice for smaller spaces as it provides hot water for 2-3 water points simultaneously and saves over 50 of available space. This unit is priced around $629.99 and includes a pure copper water tank and a BLDC variable-speed fan.

Who Should Skip These Tankless Water Heater Installations

You should not choose these models if you require a flow rate of 10 GPM or higher. None of the three selected units reach the 10 GPM threshold required to run two showers and a sink at the same time.

If you require a higher volume of water for a multi-unit commercial setting, you should look for commercial grade units. You can also find specialized options in the best condensing tankless hot water heater guide.