by • November 29, 2013 • Water Heating & Plumbing & ToiletsComments (21)13691

Rinnai’s new RH180 Water Heater VS “Standard” Rheem 50 Gallon Gas WH

  Water heaters are boring to most people, but if you’re reading my blog you aren’t like most people!  You are like me, you are a researcher.  Most likely you’re a male, between the age of 45-55, possibly an Engineer or Physician, and you are most likely handsome (guessing here).  No offence ladies, but my blog stats show this profile fits 80% of the people reading here.  Ok back to the water heaters…
   Most houses in America that have access to Natural Gas use a standard 50 gallon gas water heater like this one.  Rheem makes a pretty good unit, and I’ve used this model for a few houses over the years. 

Rheem Fury 50 Gallon Gas Water Heater

  I’ve got three issues with these “standard” tank units.

  1. Low capacity.  They are typically 40,000 BTU inputs and deliver 70-90 gallons of hot water in the first hour of use.  That is enough hot water for small 1-2 person households, but once you fill a bathtub the person showering after that might get cut short on hot water.  
  2. Low efficiency.  These standard gas tanks are between 55-62% efficient in their use of gas.  That means for every dollar of gas I spend I’m only getting 55 cents back, the other 45 cents is lost to inefficiency.  
  3. Venting.  This doesn’t affect you if you are reading this for tank replacement advice, but if you are building a new house you might have this tank inside your conditioned space and the standard metal “B” vents are terrible for combustion safety, and for air leakage. 

Finally there is a competitor to the standard tank!
I was reading one of my trade journals last night and came across this really cool new product from Rinnai!  I’m a big fan of this company, and have used their tankless units for years (including my house with an outside mounted tankless unit) so this really stood out to me.

Rinnai RH180 Hybrid Tank-Tankless Water Heater

It appears to be a smallish tankless unit that’s married to a standard 40 gallon storage tank.  Here’s a link to the Rinnai website if you want to check the details, but here’s what I like about this unit.

  • It would make a great replacement to an existing 40-50-75 gallon gas unit.  Same 1/2″ gas line, same connections, and roughly the same space needed.  It also uses a standard 4″ metal B-vent like 99% of the homes in America have currently.  Any plumber should be able to install this without special training. 
  • Their stats show double the hot water capacity of a 50 gallon gas unit.  First Hour Rating of this unit is 180 Gallons compared to that Rheem I cited above that has 90 Gallons FHR. 
  • Efficiency.  This unit is 80% efficient compared to the Rheem which is 62% efficient.  Less waste is a good thing! 

Overall this unit shows alot of promise.  I’m sure I will have a house in future that will be a good fit for this unit so hopefully I’ll have a future Post-Install review to share.  Please comment if you have any direct experience with this new unit.
UPDATE DEC 2, 2013:
I had my supplier price this for me to see how it compares and it’s about $500-600 more than a standard Rinnai tankless unit.  That isn’t “cheap” but I think for a well built unit that should last 20+ years that’s not a bad price for the performance.  If you are thinking of swapping out your standard tank and going tankless you will easily make up that $500 in extra costs for labor/gas lines/venting.  This unit is well priced and I can’t wait to install one on 2014.

Matt Risinger
Risinger Homes in Austin, TX

Risinger Homes is a custom builder and whole house remodeling contractor that specializes in Architect driven and fine craftsmanship work. We utilize an in-house carpentry staff and the latest building science research to build dramatically more efficient, healthy and durable homes.
Be sure to check out my video blog on YouTube, and follow me on Twitter @MattRisinger 
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  • Well I’m only 36, I am male, I’m neither a Engineer or Physician (I’m presently a Registered Nurse), but I’m most definitely handsome!!! LOL. Anyway, great product idea just like the LED lights you just posted about. Thanks for keeping us informed on all of the newest products!

    • Ryan, Well, you pegged “most” of the demographics! Always appreciate you reading and commenting my friend! Best, Matt

    • How much does this model sell for?

    • PeterPete, I believe this is in the $2000 range. Matt

  • I have two old (as in 13/19 years) 50-gal conventional gas fired tanks. They are installed in series (one tank feeds into the other. Don’t ask me why the builder did that). Which would be better as a replacement – a tankless unit or the Rinnai RH180?

    • My recommendation would be the RH180. Easy to swap, great output, space saving compared to two tanks. It’s a great unit for your situation. Best, Maty

  • Greetings, Matt. Thanks for this article, and even more so for the one from June comparing the Rinnai tankless to the AO Smith Vertex and the heat pump options. Great information and a lively read. We live up in Boston, and our old oil-fired steam boiler with a tankless hot water insert is dying, so for heat we’re keeping our two-pipe steam radiators and updating to a gas steam boiler since it’s too risky/troublesome/expensive to go to a condensing forced hot water boiler in our old house. We’re a bit overwhelmed trying to decide what sort of DHW system to install. An advanced hot water heater would work, but we’re leaning towards a single gas tankless system since our water is much softer than in Austin, the HW output is fine even in the winter, and the heater would go in the basement. It seems from the Energy Star ratings that the Vertex would be a more energy efficient choice than the RH180. One concern I have with both the Vertex and the RH180 is that with glass lined tanks vs. stainless steel, they won’t last very long compared to a well-maintained tankless or a water heater with a stainless tank like the HTP Phoenix line. All the new-tech storage water heaters seem pricey versus the latest tankless heaters, both in initial and lifecycle cost. (Sorry for the wordiness.) Your thoughts?

    • Greg, Very good evaluation. I would tend to agree on using tankless for DHW on it being a lowest cost, especially with soft water. I wonder if you might have issues with a cold inlet temp for water? Have you heard of the cold water sandwich effect? In Austin we rarely have inlet temps below 60 degrees so I don’t often have problems with my Rinnai with the cold water sandwich. I could see that problem being more pronounced if your inlet temps were in the 40’s or 50’s. Thanks for commenting. I wish you the best, Matt

  • Jay Santos

    Would this make $$$ sense if we are going to be selling our houses in about 5 years? Thanks.

    • Yes, I would say that it still makes sense. You’ll get some great benefits in the meantime and I expect it to be worth more at resale time. Best, Matt

  • Steve Pilkington

    I have both a new conventional water heater and a new tankless Bosch unit. How can I connect them together? The goal is to use the Bosch as a peaking unit only for high demand periods. Perhaps a temperature sensor in the tank hot water outlet to operate a control valve at the tankless cold water entry or a simple timer set for 15 minutes. A back flow preventer in the existing piping may be needed.

    • Good qustion. Never done that before. Not sure this is a great use for either unit. Matt

      • Steve Pilkington

        Ok. Similar in concept to the hybrid RH180 you discussed and to a Bosch cascaded system of multiple tankless units. I’ll keep looking.

  • Phil

    One of the issues know one seems to zero in on with these units, and the tankless models to even a greater extent, is the HUGE natural gas requirement. IIRC, this unit requires 90,000 BTU/hour. Many of the tankless models are right at 200,000 BTU/hour. The “275” gas meter is ubiquitous. Most gas companies install them as the “default” meter. They are rated at 275,000 BTU/Hour. That’s got to serve the whole house…not just the water heater. It’s just a TREMENDOUS amount of energy these units require, equal to more than 56,000 Watts for the bigger ones. You may have to call your gas company and ask for a bigger meter. In some cases, your home’s piping may not be sufficient. You really need to run a pressure drop calculation if it is to be installed very far from the gas supply. Also, anecdotally, the tankless units seem to have some maintenance issues. One or two extra service calls during the lifetime of the unit will negate any money saved due to energy use. I’m still on the fence on this one.

    • Matt Risinger

      I can see your point on this. The maintenance is not something to underestimate either. Thanks for commenting. Matt

  • Kyle Gregory

    Matt, any updates? Have you installed any of these units (rh180) yet? I’m looking to put one in my home this weekend. I’ve seen several great bias reviews, but nothing as far as actual users if they are happy or not. Like the reviews, I see the potential this unit offers, but sounds too good to be true!

    One thing I’ve noticed, it’s just shy of the 90% efficiency rating to receive any state or nat’l gov’t incentives or rebates. And Rinnia doesn’t offer the wi-fi feature that I’m seeing on other tankless models Rinnai offers.

    I’ll call Rinnia tomorrow directly to see if they can answer some questions. Thanks for the blogs!

    • Sorry Kyle. Still haven’t installed one. I’m generally using the AO Smith Vertex on my houses, but this model uses a smaller gas line which is great for retrofits. Matt

      • Updates? I just saw one of these on clearance at Lowes for a grand — trying to figure out if it’s a viable replacement for a conventional 50-gal unit.

        • Seems like a steal at $1k! I’d go for it. Unfortunately, i’ve not personally installed one as this is really a retrofit model. Let me know your experience. Best, Matt

  • ricklaborde

    I am considering a RH180P as a replacement for my existing 75
    gal propane tank heater. I am concerned with 1) the fact that I live at
    7000′ elevation and most likely need a restriction on the jet to
    accomidate for less oxygen, I am assuming that the
    existing hot water heater was working with a restricted jet but this unit has a much higher btu rating. I already have water, gas, electricity and vent at the
    current location so it should be an easy swap. Currently these are
    selling at Lowes for $999 a deal compaired to listed price.

    • Go for it! Looks like a killer deal at that price. Let me know what you think… Best, Matt