Rinnai Tankless Water Heater

If you want hot water on demand 24 hours a day, seven days a week, your best option is to get a tankless water heater. One of the more popular manufacturers of these tankless water heaters is Rinnai. This is a Japanese company based in Nagoya, Japan. It manufactures gas appliances like energy-efficient tankless water heaters, home heating appliances, and boilers. Since we’re on the topic of tankless water heaters, the best one that Rinnai offers is the Rinnai RUC98iN Ultra Series. Keep reading this article to find out why this tankless gas water heater is the best that Rinnai has to offer.

Main Characteristics

The first thing you need to know about the Rinnai RUC98iN Ultra Series is that it is an indoor type gas tankless water heater. It is best suited for both residential and commercial applications. It can either use propane or natural gas and offers multiple venting options. This versatile tankless water heater is not only bigger and heavier than the most home tankless water heater brands, but it is also more powerful. It has an energy factor of 0.95 whether you use it with natural gas or propane. For those who don't have a clue what that means, that is a higher value than the average gas-powered water heaters and it means that it is very energy efficient. It is also an Energy Star-certified heater. It has a minimum-to-maximum gas burn rate that varies from 15,200 to 199,000 Btu. Aside from that, the heater has very wide hot water flow rate range is at 0.26 to 9.8 gpm. It has a minimum activation flow rate of only 0.4 gpm. These numbers mean that this tankless gas water heater can power multiple faucets and showerheads and can also be used in multi-bathroom households without worrying about interruption to hot water flow. The standard model is capable of heating water to temperatures of 95 to 140 degrees Fahrenheit, while the commercial model can provide water as hot as 185 degrees Fahrenheit.

Pros and Cons


  • Occupies less space than other water heaters even though it is quite bulky
  • Energy efficient
  • Above average hot water flow rate
  • Can simultaneously provide hot water to multiple faucets and showers
  • Very versatile
  • Very durable


  • Requires professional help when installing
  • A bit bulky
  • Expensive


Probably the main reason why the RUC98iN is the best Rinnai tankless water heater is because of its design. Its dimension of 26  x 10 inches allows you to easily find a place to install it. Plus, it only weighs 61.7 pounds. Although it is quite bulky, its compact and sleek design can offset the size. But make no mistake, it is not a lightweight water heater. This tankless water heater has a gunmetal gray exterior that provides the extra weight. Rinnai also placed the controls of this tankless water heater on the lower lip of the front panel for easier access. It has a power button, water temperature and gas control buttons, and a digital display, just what you would expect from any control panel. You can also lock the temperature button to prevent unauthorized access, which is an excellent child-proof feature.

Special Features

The most redeeming feature of the RUC98iN is its capability to power multiple faucets and showerheads. This will allow you to use multiple bathrooms or faucets in your house simultaneously without interruption to hot water flow. Plus, as you can see, it is using tankless technology. That means it only operates when hot water is needed. You will be able to save on energy and utility costs significantly. Lastly, this tankless gas water heater gives you options at the time of installation depending on your needs, which will provide you more efficiency in terms of gas consumption.


For residential models, it has a Limited 12-year on the heat exchanger, 5-year warranty on parts and a 1-year warranty on labor (plus an optional 5-year warranty on labor). For commercial units, it has a limited 5-year warranty on the heat exchanger, 5-year warranty on parts, 1-year on labor (plus an optional 2-year warranty upgrade on labor).


The RUC98iN is the best that Rinnai has to offer because it is a sleek and highly efficient gas tankless water heater that can use either natural gas or propane. It also comes with multiple venting options. The downside is, it is a bit bulky and can be tricky to install. It is one of the most powerful tankless water heaters on the market today. Plus, it does not make any noise when heating the water. It is what you would expect of Rinnai in terms of service, maintenance and of course the quality.

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