Rinnai R75LSi, a Rinnai tankless water heater review

Published in Green Product Reviews, Tankless Water Heater on 9th October 2011

Last updated on April 18th, 2021 at 04:00 am

Image from Amazon

Looking to invest in a high-end tankless water heater like the Rinnai R75LSi? The RL75LSi is part of a range of high-end tankless water heaters series by Rinnai. 

Tankless water heaters are products with benefits to help you save energy and lower your carbon footprint. Hence, here is my unbiased review about Rinnai R75LSi.

Benefits Of Owning A Rinnai R75LSi

Production Capacity of 7.5 GPM

It has a production capacity of 7.5 gallons per minute (GPM) of hot water. Production of hot water has also been said to be almost instantaneously by consumers upon the opening of the faucet, with a satisfying whoosh sound!

Compact and sleek design

Rinnai R75LSi is a tankless water heater with a compact and sleek outer design that allows for easy installation indoors in any room for your home or office buildings. The Rinnal R75LSi can also be installed in mobile homes.

Digitally controlled temperature design

Adjusting and troubleshooting of this Rinnai tankless water heater is also controlled digitally via the standard MC-91-1US controller and ranges from 98 Degrees Fahrenheit to 140 Degrees Fahrenheit. Like all LS models of Rinnai tankless water heater, it comes with a commercial heat exchanger that allows for installation indoors for residential, commercial and even for mobile homes.

The consumer can also upgrade the controller can also be upgraded to MCC-91 for commercial purposes that will increase the maximum temperature to 160 Degrees

Runs on Natural Gas or Propane

As compared to oil and coal, natural gas is the cleanest fossil fuel in terms of emission, with the least emissions in terms of sulphur dioxide and nitrogen oxides, with virtually no ash or particulate matter released. Propane is also earmarked to be a viable alternative fuel source.  

Both fuel sources release lower levels of carbon dioxide, carbon monoxide, and other reactive hydrocarbons as compared to oil and coal therefore will have a lesser impact on the environment.

Green Product

Rinnai R75LSi is an Energy Star certified product with a thermal efficiency of 84% and energy factor of 0.82. Installing this tankless water heater also qualifies you for 300 USD under the non-property energy property tax credits. It also meets California and Texas NOx emissions standards. This applies to all Rinnai tankless water heaters except for Rinnai R98LS.

The Rinnai R75LSi, like all Rinnai products, also last much longer than those traditional tank water heaters; up to 20 years more. The primary components that make up all Rinnai tankless water heaters like the digital panel and heat exchanger are also all recyclable making it a green product.

Summary of Specifications for Rinnai R75LSi

DimensionsHeight = 22.9 in.
Width = 14.0 in.
Depth = 9.6 in.
Weight = 50 pounds
Installation ModeIndoor, Residential and Commercial. Can be connected to another unit via EZConnect®.
Production Capacity Maximum of 7.5 GPM
Temperature Range98-140 Degrees Fahrenheit
98-160 Degrees Fahrenheit (Commercial)
Minumum/Maximum Gas Rate (BTUs)9900 to 180,000 BTUs
Energy Star Certified Yes. Possess an energy factor of 0.82.
Warranty12 Year Warranty on Heat Exchanger, 5 Years on Parts, 1 Year Labor for Residential Installation

How does Rinnai R75LSi rate on popular websites?



30 reviewers at Amazon gave Rinnai R75LSi 4.1 stars out of 5 stars. Comments were mostly positive with 21 reviewers giving it 5 stars out of 5 stars.


A survey carried out in 2007 by BuilderOnline.org showed that Rinnai tankless water heater was ranked first in terms of quality ahead of popular brands like Rheem and A.O Smith.

 (Download results of the survey here)


Customer Reviews for Rinnai R75LSi

I have read reviews for Rinnai R75LSi by verified purchasers and summarised them below.


The price of the R75LSi was mentioned to be an issue. To help you to find a more economical and suitable models from Rinnai for your household, there is an option on Rinnai website that aid you in selection. Click here to access this service.

Installation and assembly

Installation of this unit was mentioned to be more expensive with additional venting and materials due to differing installation procedures from a conventional water heater. So it will be good if your installer has prior experience in installing a tankless water heater. The list of licensed professionals aka Rinnai ACE (Advanced Comfort Expert) segregated by regions to carry out installation and servicing of Rinnai products can be found on the Rinnai website. Click here to access the link.


Positive comments include its space-saving design, consistent hot water production, and almost instantaneous hot water upon turning on the faucet. Other positive reviews include visible savings on the utility bills and ability to support a wide range and capacity of usage.

Some negative feedback include brief initial spurts of cold water, amount of water wasted caused by the delay between turning on the faucet and getting hot water.  

A related point to consider is the temperature of the water supply in the region where you are based in; if your region is too cold, the maximum temperature of 160 Degrees Fahrenheit might not be sufficient.

Rinnai has an online service that aid you in choosing a suitable model by region, size of your household and fuel source. Click here to access this service.


There is a limited warranty that comes with the Rinnai R75LSi. The heat exchanger is covered for 12 years for residential usage only, 10 years for residential and space heating, and 5 years for commercial settings. There is a 5 year warranty for the other parts and 1 year labour warranty coverage.

Note: In order for this warranty to apply, it is required that a licensed professional who has attended a Rinnai installation training class did the installation of this water heater. Click here to access the link provided by Rinnai to find the licensed professional or ACE (Advanced Comfort Expert) in your region.

Warranty document for Rinnai High Efficiency Plus Tankless Water Heater(Download the Warranty document here)

Best Deals for Rinnai R75LSi

During my research on the Rinnai R75LSi, I discovered that the best place to get it online especially vis reputable sites like Amazon. Comparison between online sites that carry this tankless water heater also reveal that Amazon generally offers a lower price ensuring you get the lowest prices and the best deals for this product.

So if you are interested, here’s the link offered by Amazon for Rinnai R75LSi: Rinnai R75LSi Best Deals

(Download the Specification Sheet for Rinnai R75LSi here)

Operation and Installation Manual for Rinnai R75LSi(Download the Operation and Installation Manual for Rinnai R75LSi here)