Smart Water Heater 2021 Update

We just purchased a vacation home that, as luck would have it, has a couple outdated tanked water heaters. I need to replace them soon. Since it's a vacation home, I'd love to integrate with Hubitat for the purpose of (1) remotely managing temperature; (2) setting modes; and (3) managing a whole-house recirculation pump, all in the most efficient way possible. Space is not a particular concern.

I can see some have had luck with Rheem Econet although it appears they switched their integration lately. I thought it might be time for a refreshed view.

  1. Thoughts generally on tankless?
  2. Opinions on how worthwhile to try to integrate with home automation?
  3. POV on specific product(s)?

Ready, go....

We’ll need a lot more details before one can formulate a strategy. Does the house currently have a natural gas or electric hot water heater? Or possibly a boiler system that provides heat and hot water? Does it already have a recirculation pump?

Converting a traditional electric hot water heater over to a tankless electric hot water heater would require quite a few new 240VAC, high current circuits to be run. This can be pricey depending on your current electrical panel’s capacity. When I investigated this option a few years ago, it was way too expensive.

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They require more maintenance, and are terrible option if you have lots of minerals in the water.

In my case, my ground water is so cold I would have a hard time getting the water hot enough when running faucets wide open. Or I would need an astronomically large unit to get enough temp rise.

Tankless make a bit more sense with natural gas, but even then they sometimes require a larger gas meter or piping to the meter. And that isn't cheap or easy to upgrade.

And if you are in a cold climate, and have to drain the heater, you better check to see what a tankless would involve to do so. I bet it would be more involved than a tank-type.

I am fairly happy with it. I don't do extensive automations with Hubitat integration, but I do mess around with changing modes (mine is a hybrid) depending upon outside temp and that function is lacking in the Rheem app. The Rheem app generally works OK after they did some updates a year or so ago, so that is another way to control it.

I think it was almost a year ago that it changed, so not terribly recent. Dominick @dman2306 did an excellent job figuring this new version out. Kudos to him for keeping it operational.

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One of my neighbors got this done ~10-12 years ago. A unit comparable to a 50 gallon tank water heater required 4x40A circuits. She was happy with the conversion for a couple of years, but then the unit failed for the reasons described by @neonturbo. Which was when she discovered that the warranty required twice annual cleanings by a plumbing company licensed to work on that particular heater, while she had her regular plumber flush it out with vinegar to remove scale.

Bottomline - it was pricy ~$1000 for the heater, $2000 for the new circuits to be run (+ drywall repair, painting etc. etc). She is back to using a tank water heater now. I don't remember the name of the tankless heater, but tank heater she has is the Rheem Marathon, which doesn't have a metal body.

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Also just one general suggestion regarding tank water heaters. I would be hesitant to lower the temperature much lower than 140F, because Legionella (the etiologic agent of Legionnaire's disease) grows fairly well at lower temperatures.

Also, constantly shifting the temperature to <140F and then to >140F is a good way to select for Legionella variants that can survive at higher temperatures.

Because I do turn my heaters on/off using a z-wave relay, I drain them once/twice a year, and treat them with a little bleach or hydrogen peroxide before I refill them.

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I view them similar to solar panels. Very expensive to retrofit from traditional, requires much more maintenance and upkeep, You will not break even on the expensive upgrade at all if you don't have either a semi-large family size in the house or stay in the same house for at least a decade, while hoping the unit lasts this long before failing.

As far as smart water heater, I have an Aquanta wifi controller (this way it can be removed and replaced if the water heater gets replaced) on my cheap run of the mill tank water heaters, which I have set to a certain time of day turn on and off, and it has it's own algorithms that get created by your usage on optimal times for it to turn on during the day. I guess you could control it via IFTTT but I haven't really found the need to.

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This is interesting. So, counterpoint: I've been running a Rinnai tankless on Propane, with Well Water for 11 years, no repairs, no faults, and a total install cost of <$3K, for System, propane tank, and a water softener, as I had enough hardness that it seemed advisable (significant mineral buildup, but no iron or other contaminates). The Rinnai is supplied with water from our well using a continuous pressure well pump system (no tank) and is capable of 6.5-9GPM or more of steady hot water flow. I don't recall my incoming water temp, but it wasn't extremely cold.

I run it at 130 degrees, and didn't have a service/flush for 10 years.

In comparison, the tanked water heater it replaced had had the elements replaced at least 10 times, by the record on the side of the tank when I bought the house.

For my money & comfort, you couldn't pay me to take an electric tank heater. My experience with electric tankless while in the UK says no to those as well.

However, I see others clearly disagree. So as usual YMMV!

My house is in Northern Virginia, and occupied full time by 4 adults.

The shower is used roughly 6 times per day (total, not each), and we don't limit use of hot water for other functions. We also have Solar, so based on this thread, my judgment is suspect! :smiley:

S.

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I would agree with you. Propane and natural gas tankless heaters are good. And good plumbers swear by the reliability of Rinnai heaters.

My comments were directed at electric tankless heaters - these are a definite no-no in my book.

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How much has your usage on propane increased because of the extremely high BTU capacity of these tankless heaters from before the tankless until now?

I should let @scottgu3 answer, but people whom I know who replaced natural gas water heaters with natural gas tankless heaters have never complained about increased natural gas bills.

Typically, a 50 gallon tanked heater is about 40-50,000 BTU. And it maintains 50 gallons of water at the set point year-in year-out.

Tankless heaters are 10 times as much in their heat demand, so 300-400,000 BTU is common, but the heating is often for very short periods of time.

For someone like me, who lives alone, I would probably use less fuel with the tankless. But I cannot get gas service where I live, so the point is moot.

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This is why last time I did the math on these I went with a wifi controller instead to only heat up the water during the "general time" it was going to be used. You get somewhat of the similar savings of not heating the water 24/7, with only spending $200 and $400 for a new heater every 7-10 years versus $3k.

Based on the stats of that controller the heater is only around 100kWh or about 10% or less than my total electric bill with these settings, (only 2 in the house)

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Agreed 100%.

I do something very similar. I use a 240V, 80A relay whose coil is controlled by a z-wave outlet (for each of my two heaters). And I also have noticed a substantial saving in my electric bill.

TO make @waynespringer79 's point further, this is the electricity consumption (daily) in kWh for one of my water heaters. Before turning it for select amount of time each day, the average consumption about 5 kWh/day. Now it is about 3 kWh in the summer, and 4 kWh in the winter.

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My 50 gallon hybrid averages less than that for two of us, and we aren't shy about water use or washing clothes in hot water. I keep it at 135 degrees. And it helps to cool and dehumidifies the house in the summer, so I get some benefit there too.

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Good question!

I only have Propane for the Rinnai, and my typical propane cost is between $120-150 per quarter. It fluctuates a fair bit due to the cost of propane being tied to Gasoline refining, but my usage is fairly consistent.

S.

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Here is the sats from Aquanta


Yearly

Daily

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Fair points. I freely admit, I didn't buy mine for any sort of cost savings. I love it for its reliability, low space requirement, and almost literal unlimited amounts of hot water.

Also, I don't have to mess with turning it on or off, and during power outages, I can run it pretty much as normal without drawing down my batteries much.

I would prefer natural gas to propane. If I had natural gas, my operating costs would be substantially lower!

S.

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They are definitely a much more convenient option, especially if you have a larger household.

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Also, to be totally fair, I bought mine in 2008, and the Rinnai was only $900-$1000 at the time. Much of my cost was the propane tank, gas plumbing and installation of the tankless, the softener and removal of the old unit. Today, the cost of the Rinnai is similar for an equivalent model, and a replacement would probably be $1500 installed.

Still a lot higher than a conventional WH. But doing the math, my Rinnai has been going for going on 13 years trouble free, so I can live with that. :slight_smile:

But I think a lot of good points have been made about other factors that really drive differing solutions for each of us. I recall reading with utter astonishment in another thread where someone posted that they were going on demand Electric because....Solar. My mind couldn't quite grasp how he got there, but he did it, and it seems to work for him!

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Straight electric of any kind vs a heat pump water heater, the heat pump always wins, by a lot. Like straight electric is by nature 100% efficient, but a hybrid typically runs between 300% and 400% efficiency. So even with solar, I don't get wanting a demand electric...

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I have a Rinnai tankless, runs on Propane, and have been happy with it so far. I am in the South and I actually have the tank mounted on the outside of my house. We don't have to worry too much about freezing. We have only had it for 10 months now so I can't speak to longevity. Hopefully it will last as long as Scottgu3's

It's just two of us. The tank water heater that was in the house was installed in the laundry room and we wanted it out. The original plan was to move it into the garage but after reviewing the tankless I decided to give it a try. Mounting it outside saved quite a bit on the install since there is no venting required. The unit we got was $1200.00. The plumbing was pretty easy as the unit basically sits on the outside wall right behind where it was in the house.

I used 45 gallons of propane in 6 months, we also switched from an electric to gas cooktop. When the tank was initially filled the price was $1.94/gal. So it's costing about $14.50/month, or about 137 kwh/month based on my current electric rate. That is cooking and hot water. This is less than the estimates you see online for a standard tank hot water heater.

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