Rinnai RUC98iN Review

As an Amazon Associate we earn from qualifying purchases. Learn More.

If the Rinnai RUC98iN Natural Gas Tankless Water Heater isn't on your short list, you might want to take a second look. This powerful condensing heater is not only one of Rinnai's most popular units, but also one of the best tankless water heaters we have tried, read below and we'll show you why.

Tankless water heaters have gained in popularity recently because they are energy-efficient appliances that can save you money on your monthly utility bill. They require less space than a tank-style water heater and they're better for the environment.

Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe

Rinnai RUC98iN Ultra Series natural Gas Tankless Water Heater

The Rinnai RUC98iN is an indoor-only tankless water heater. It has a sleek exterior with a digital display and controls located within easy reach. The heater is Wi-Fi capable and can be operated wirelessly by your smart phone.

Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe
  • INDOOR installation only. Fuel Type: NATURAL GAS.
  • Concentric or PVC venting option
  • Up to 0.96 Energy Factor/Up to 0.92 Uniform Energy Factor
  • The space-saving design allows Indoor Installation type
  • Ultra low NOx emissions

This unit is part of Rinnai's RUC line of tankless water heaters which are designed to be ultra-efficient and emit a very low amount of nitrogen oxide. Which results in a water heater that is better for the environment since it produces less toxic greenhouse gases.

All RUC models have a number of advantages that make them attractive choices for cost-conscious consumers. With a high Uniform Energy Factor (UEF) of at least 0.92, the heaters within the RUC line-up are quite energy efficient.

The higher the UEF rating, the more energy efficient the tankless heater, so you can expect that the RUC98iN will use less natural gas to heat the water in your home.

Like the majority of Rinnai products, the RUC line-up comes recirculation pump ready. When enabled, this feature will not only allow you to have instant hot water, but it'll also help you save hundreds of gallons of water each year.

The RUC98iN was discontinued by Rinnai in September of 2019. However, the RU199iN is a direct replacement for this model. See below for more details.


The RUC98iN is an excellent example of an energy-efficient tankless water heater. It has a high UEF rating of 0.92 and uses an electric ignition system, which consumes less energy than a traditional pilot light.

Like the majority of Rinnai products (read a review of all Rinnai tankless heaters) the RUC98iN is Wi-Fi capable and can be controlled by a proprietary app. When the system is in use you'll be able to set timers for the water heater, control when it turns on and off, and even lock the water temperature to prevent others from changing your settings or wasting energy.

One major advantage with using Wi-Fi is that you can register your tankless with a professional technician. He'll be able to monitor the performance of your appliance, and should you require repairs, he'll know exactly what the problem is before he pulls into your driveway!

  • Maximum GPM: 9.8
  • UEF Rating: 0.92
  • BTU: 199,000 maximum
  • Location: Indoor
  • Venting: Concentric or PVC
  • Energy Star Certified: Yes


The RUC98iN is a condensing tankless water heater, which, put simply, means that expensive venting isn't necessary. However, what makes this model unique is the dual venting design.

There are two venting options available. Your installer will have the ability to use either concentric or twin-pipe PVC venting, which ever works best to meet your individual installation needs. 

Rinnai is the only manufacturer that offers dual venting options. It's a feature that will save you both money and time.


Consult with a Local Plumber

Get FREE Quotes Today

Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe

Rinnai RUC98iN Price

Since the RUC98iN is a condensing tankless water heater, you can expect it to carry a higher price tag than non-concentric heaters. What's the difference between condensing and non-condensing? Well, actually quite a bit. But without going into a lot of detail, the main difference is how the acidic exhaust gas is processed.

Non-condensing tankless heaters are less expensive to purchase, but  require expensive stainless steel venting to handle the corrosive exhaust. This drives up the costs of installation, and often results in a higher overall project price.

Where a condensing tankless water heater is more expensive to purchase since they handle the acidic exhaust within the unit, and less expensive to install because the exhaust can be vented using inexpensive PVC pipe.

We highly recommend purchasing a condensing tankless such as the RUC98iN. The technology is superior and you'll frequently have more bells-and-whistles. And, when you think about it, wouldn't you rather put your money into your tankless appliance instead of your venting?

If you are looking for a cheaper model, then read our Rinnai RL75in review

Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe
  • INDOOR installation only. Fuel Type: NATURAL GAS.
  • Concentric or PVC venting option
  • Up to 0.96 Energy Factor/Up to 0.92 Uniform Energy Factor
  • The space-saving design allows Indoor Installation type
  • Ultra low NOx emissions

Where to Buy

Rinnai sells their water heaters at large box stores such as Lowe's and Home Depot, as well as through online retailers like Amazon. Always make sure to purchase from an authorized Rinnai dealer.

Many homeowners prefer to purchase their tankless water heaters from a professional dealer who will come to your home and assess your needs, recommend the right unit for your household, and install it for you. 


Consult with a Local Plumber

Get FREE Quotes Today

RUC98iN Warranty

Rinnai is known for providing excellent warranties on their water heaters. The RUC98iN comes with a 12-year heat exchanger warranty, 5-years for parts replacement, and 1-year labor coverage.

Proper installation is essential for the warranty to be valid. Many homeowners like to save a few dollars and do the installation themselves, but these units should be installed by a qualified professional who has been trained by Rinnai.

Purchasing a tankless water heater is an investment that, if properly maintained, will be operating for 20+ years. Saving a few dollars today is not worth losing years of service life or voiding your warranty. 

Rinnai RUC98iN Problems

The RUC98iN, like all of Rinnai's tankless water heaters, are excellent products. If the appliance isn't functioning properly an error code will display on the front panel, and your owner's manual will identify the problem so you can determine when to call for service.

If you use register your tankless with a service professional, any issues will be transmitted to his office immediately. Whether your unit requires maintenance or repairs, your service technician will be prepared when they arrive.

Regular Maintenance

All tankless water heaters require regular maintenance. They also need to be flushed to prevent limescale build-up. The process of flushing isn't difficult and can be done by the homeowner.

Many homeowners choose to have a professional flush their tankless heater and complete an annual inspection at the same time. Rinnai offers excellent support through their website with answers to many frequently asked questions. In addition, they can be reached by phone or through email by filling out their contact form.


Consult with a Local Plumber

Get FREE Quotes Today

Rinnai RUC98iN Energy Efficiency

Rinnai offers a few models with a UEF (Uniform Energy Factor) up to 0.95, and although the RUC98iN doesn't quite reach that mark, it does turn in a very respectable 0.92 UEF rating.

Compared to other gas tankless water heaters on the market, 0.92 is quite high and considered an excellent energy efficiency rating.

RUC98iN Energy Star Rating

There are very strict requirements that need to be met for an appliance to be Energy Star certified. The RUC98iN meets these requirements, and therefore can sport the Energy Star blue logo.

You can have peace of mind knowing that you're not only saving money each month on your utility bills, but you're also operating an appliance that's better for the environment.

Rinnai RUC98iN Installation

Installation is far less complicated with the RUC98iN because it utilizes condensing technology and is designed with dual venting options. But that doesn't mean you should install it yourself.

Hiring a Rinnai trained professional will ensure that your new tankless heater is correctly installed and the warranty is not compromised.

These are complex appliances which require knowledge in electrical, ventilation, and plumbing systems, as well as natural gas. The money you spend having the system installed is well worth the investment.

RUC98iN Manual

An owners manual will come with each RUC98iN tankless water heater. These manuals are packed full of useful information from troubleshooting to operating instructions, and you'll likely need to refer to it from time-to-time.

Rinnai offers manuals to download on their website as well as technicians to answer your questions, however, there are also third party sites where you can download a manual if you should misplace yours.

The Rinnai RU199iN

As we mentioned above, the RUC98iN was discontinued. However, it was almost immediately replaced with a more advanced model by Rinnai. Like its predecessor, the RU199iN is categorized as a Super High Efficiency Plus model, although it goes above and beyond in several respects.

For starters, it has a slightly higher UEF rating of 0.93 compared to the RUC98iN's UEF rating of 0.92. This might not seem like much, but this extra energy efficiency can eventually pay dividends in terms of water heating bill savings over the long-term.

Rinnai RU Series Sensei SE+ Tankless Hot Water Heater: Indoor Installation, RU199in - Natural Gas/11 GPM

Like the RUC98iN, it's recirculation capable and it's powered by natural gas with a maximum BTU generation limit of 199,000. In other words, it can get just as hot even if it's slightly more efficient with the energy it takes and produces.

What might be the biggest selling point with the RUC98iN, is it's maximum GPM flow rate. Although the RUC98iN's max rate was an impressive 9.8 GPM, the RUC98iN can deliver up to 11 GPM - enough for even the most demanding households.

Like the RUC98iN, it's Wi-Fi enabled, and it's also rated as Low NOx, so they're about equal in that respect. It also has dual venting options for vertical or horizontal orientaions in your home. 

In terms of warranty options, you can expect about the same for the RU199iN as you get for virtually any other Rinnai tankless water heater. In a nutshell, compared to the RUC98iN, the RU199iN is:

  • A little larger
  • Has a higher maximum flow rate (GPM)
  • Is slightly more energy-efficient (UEF)
  • Has the same green aspects
  • Has the same venting options
  • Also uses natural gas

This is a great replacement in our eyes, especially if you can't find the RUC98iN, as exisitng models will likely be depleted sooner or later. The RU199iN is the offical replacement by Rinnai, so it makes sense that it serves a similar purpose and is basically just a slight upgrade in terms of energy efficiency and flow rate.

Rinnai RU199iN Condensing Tankless Hot Water Heater, 11 GPM, Natural Gas, Indoor Installation
  • Endless Hot Water: Our tankless hot water heaters offer unlimited whole-home hot water flow and come equipped with Circ-Logic for pairing with an external pump to reduce wait time for hot water via scheduled or on-demand recirculation
  • Energy and Space Efficient: The tankless design of this small hot water heater saves on space and conserves energy as it heats only when necessary
  • Optimal Water Pressure: With a hot water flow rate of up to 11 GPM, this tankless water heater provides a powerful, constant stream that can accommodate up to 7 appliances at once
  • Professional Installation Recommended: Visit the Find a Rinnai PRO page on our website to locate a qualified technician in your area to install your water heater; We do not recommend installing a water heater without a technician
  • Guaranteed to Last: 15-, 5-, and 1-year residential for heat exchanger, labor, and parts, respectively; Wifi monitoring available with Controlr module (not included)


Consult with a Local Plumber

Get FREE Quotes Today

Last update on 2024-04-16 / Affiliate links / Images from Amazon Product Advertising API

Related Posts