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Rinnai R85e Tankless Water Heater Review

We just installed two of these on a house we built here in Austin, TX so I thought I’d give you a review of this product.
First, let’s talk briefly about the merits of tankless water heaters. The manufacturer mainly touts their energy efficiency and their ability to provide “endless” hot water. I would also say that space savings, carbon monoxide safety, and longevity are big selling points for me. I estimate that annual gas savings will be between $75 and $125 per year for most installations. You don’t have standby loss with these units and they are generally more efficient at converting gas BTU’s to hot water than their tanked counterparts. The endless hot water ability is nice if you plan to have a few teenage kids at home who are taking back-to-back showers but I don’t see that as a main selling feature for most of my clients. My favorite thing about this particular model (R85e) is that it is mounted on the outside of the house. I’m doing a remodel of my 30 year old house and the 40 gallon water heater was in the laundry room taking up space. By hanging it outside, I’ve gained usable floor space inside. Also, with this unit being mounted outside we have no metal flue going through the house. This eliminates another hole in my thermal envelope (breaking the attic insulation), eliminates another penetration in my roof (one less leak possibility), and eliminates any possibility of back drafting carbon monoxide into my home (it CAN happen). I also like the fact that they are supposed to last upwards of 20+ years. That’s double the life expectancy of a tanked heater. One last plus, they’re made in Japan! I have to admit that I love Japanese manufacturing.
Ok, now for the not so good. First, they’re more expensive (you do get what you pay for). This unit runs between $1100-1300 for this exterior mounted model. However, look for rebates, our local gas utility gives $300 back and I believe you can claim $300 on your Federal Taxes (See your accountant). Next, you need to pay for the beauty cover. That’s the white cover that extends about 18″ below the unit and covers the exposed piping. I hate that they don’t tell you about this extra $100 expense till you’re paying for the unit at the supply house! Lastly, they do require maintenance. The boilers on these units are about 5x the engine size of a tanked heater which allows them to heat enough water “instantly” to run 3 appliances (faucet, shower, dishwasher, etc) at one time. This huge engine needs periodic de-scaling that is accomplished by pumping vinegar through the boiler once a year for an hour. I would guess that most plumbers would charge $100 to $200 for this maintenance. Rinnai says that needs to be done annually. If you’re my customer I need to tell you to follow the manufacturer’s recommendations so you don’t void the (rather long) warranty. If you are not one of my customers I’d say use your best judgment and don’t go longer than 18-36 months between servicing. One last item on the down side, use a plumber that’s actually installed one of these before! They are a bit more complicated to install and they take an electric feed so you’ll need an electrician to complete the process. The electric feed fires the boiler and helps with frost protection. (They’re good to -20!) Oops, one more thing, they take a huge gas line so make sure you figure that into the cost too.
Lastly, let’s talk about actually living with one of these. If you are reading this post and have lived with one please add your own comments to this blog. I am just now installing an R85e in my personal remodel so I can only comment from previous customers who have lived with this unit. Generally speaking, most people won’t know any difference between living in a home with a tankless heater vs one with a traditional tanked unit. They have a cool remote temperature module that you can set your tankless’s output temp from a location in your house, but other than that most people won’t know. The only two use issues that might be different are the “cold water sandwich” effect and the reduced output if you have many fixtures on at once. The “Cold Water Sandwich” means that in a traditional tanked heater when you turn on a fixture (say to shave) and turn that fixture on/off/on over a period of say 20 seconds you’ll always have hot water in your water line. In a tankless situation, you flip on your faucet and there is a paddle wheel inside the unit that spins and tells the boiler to fire up. When you turn that fixture off again the boiler stops. Then, when you open it again there is a brief delay before the heater fires up again. So, when you off/on/off/on your fixtures you trap some cold (er) water in between hot water. If you were showering an doing this off/on/off/on you’d notice more of a temperature difference with this tankless unit compared to a standing hot water tank where the line always pulls from a hot tank of water (assuming it’s not out of hot). Did I explain that well enough? Here in Austin, TX that’s not a huge concern because our water from the street coming into the house is around 65 to 70 degrees F year round. In say Minnesota if you had 40 degree water coming in from the street in the winter that cold water sandwich would be a lot more noticeable! Ok, back to the reduced output. This R85e goes up to 200,000 btu’s of power which is about 5 times that of a conventional tanked unit, but it can only generate so much hot water at a time. Generally speaking, here in Austin my R85e unit can run 3 (2.5GPM) fixtures at a time without slowing down. If I were to open a fourth shower head, for instance, the tank can’t heat 10GPM so each of those 4 shower heads would have reduced flow down to a total of around 7.5GPM. This is mostly a non-issue unless you have a large house with lots of occupants. If you do have a big house, you might need two of these units to properly supply hot water for that house (as was the case in a recent job of ours).
So, let’s emulate the European and Japanese who have been using these for the past 20+ years and finally dump those inefficient tank style heaters for good! I think this is an excellent product and I try to install one in everything we build.