I have a non-smart water heater that I want to automate so that it does not heat all the time.
I want to automate it with a schedule based on our normal routine of needing hot water, which is fairly predictable. I have found a way to integrate a Zooz smart switch (Z-wave) to turn it on/off, but I am looking to see if there is a recommended way or app to schedule the on/off times for it? Ideally I would like for it to consider our Time Of Use plan for electrical rates. So basically it would be turning on/off the Zooz switch as needed, but other than a straight "turn on at 5am, turn off at 10am" rule sets, I was hoping for something more elegant.
Any suggestions on apps for setting this up & maintaining / changing it easily?
I guess it all depends upon how complex you want to get.
Do you want to only heat during off-peak rates?
Do you want to incorporate heating when say a washer or dishwasher is on, maybe incorporate a power monitoring plug.
What about when you have guests over, or weekends?
Is your electrical rate different Winter vs Summer? (mine is)
How about incoming water temps, I know I need to heat a lot longer in the Winter due to nearly freezing cold water, so maybe you would have to start earlier to achieve the temps you need.
By the way, watch the water temperature, water that sits warm like this is a breeding ground for Legionella, you really should maintain temps high enough to kill it.
And is this gas or electric? I don't know of any electric water tanks that can run off a Zooz plug. (Zooz is 120V 15A, most electric water heaters are 240V 30A)
How old is the water heater? If you really want to save electricity, get a Hybrid water heater. It cut my bill by many hundreds of dollars a year compared to my older electric only water heater.
It's wifi, I believe it has limited integration with IFTTT, but I don't bother trying to integrate it to hubitat. I just have it set on scheduled timers for on/off. It also learns your usage patterns and will build an algorithm to automatically reduce heating the water when you don't normally use it.
It also has nice graphs in the app that chart your historic electrical usage. I've had it about 4 years now and can retrieve the usage from all the way back then if needed.
The best benefit to using this over smart water heaters is you can continue to save money buying the cheaper dumb heaters and just swap this out from your old one to the new one and recycle the smarts from water heater to water heater.
I've never really understood this thought process myself. If you let water cool it takes a lot of energy to heat up the water in the tank...(Let's assume a 55 gallon tank). Far more energy then it occasionally coming on to top off the hot water in the tank. Add to that the risk of Legionella, I don't see a real benefit to shutting it down.
I agree with those comments regarding the growth of Legionella bacteria in a tank filled with tepid water.....this is a very real concern. Anything less than 120deg F and you run the risk of this happening.
Another reason not to shut off the water heater is that the stress on the tank of repeatedly cooling and heating over time, with the resulting expansion and contraction, may lead to premature failure of the tank.
This. Unless you're turning it off during a week+ long vacation (and then flushing it when you get back), I don't see where the savings would come from. The water heater is going to lose heat (energy) at about the same rate regardless of whether it's on or off, until the water gets much closer to room temperature (with the accompanying danger, as mentioned), and that takes days if hot water isn't being used. All that lost heat needs to get replaced. Whether it's a small bit every couple of hours or a larger amount every day doesn't make much difference.
If it's electric, and you're metered differently for peak/non-peak, there might be an advantage for only heating during off-peak.
This same conclusion led me to this heater (before Rheem bought them). The Marathon folks took on the cathodic decay and heat loss of a typical water tank as a challenge. It was a daring experiment which I think they've finally got right.
The energy savings I've considered is not about lowering tank temps below 120F but about pre-heating the inflow water through cheaper means like solar gain. Once the water in this tank is hot, it STAYS that way without a lot of "topping up" (the temp). It's like the "Yeti" of water heaters.
I actually think you can find even better insulated H2O heaters these days, but I don't know of any that combine good insulation with the corrosion advantages of plastic. I know, it's hard to believe that plumbing and heating a plastic tank isn't fraught with problems...but it doesn't seem to be in my experience with this tank.
Not cheap, but I've had it FOR YEARS without any concern besides heating element replacement (oh, that's another thing...I replaced the original elements with their lowest wattage elements to reduce hard water precipitate and increase element longevity).
2 years apart, not correlated with hot water use, no specifics on timing or water heater used.
It's strange that Aquanta's web site shows it installed on a water heater with no pipe or overflow insulation, which is much larger source of heat loss.
A clock-timer, used to de-energize the tanks from lO p.m. until 5 a.m. each day, was found to reduce losses by 0.050 and 0.025 W/°F for the standard and energy-efficient models respectively. The timer served to delay night-time energizations of the tanks until morning. However, the slight reduction of tank temperature during the night resulted in savings of only 3 percent of total standby losses. ... It is apparent that for no-flow standby loss reduction, the use of a clock-timer is marginal at best.
Standby losses from exposed piping averaged 0.204 W/°F. Piping losses were approximately 12 percent of the losses from a standard un-wrapped tank, and approximately 22 percent of the losses from an energy-efficient tank. Pipe insulation appears to reduce standby pipe losses by over 50 percent.
That's a older paper (1984), if you can find a newer one, I'd welcome it. There are a lot which reference timers on recirculating systems, but that mostly applies to commercial applications.
My house has not changed in any drastic way of water usage for at least 5 years. The 2 years apart is intentional. The first year installed was intentionally done with no timer used so that I could get a baseline of what the typical energy usage was. I made the change to using the timer in mid-2020, therefore using the full year of 2021 vs 2019 is a true evaluation of a before vs after.
Hey all. I was kind of hoping to just find a good timer app -vs- generating all the input on whether it makes sense or not. :). This is kind of an experiment for me, and I am familiar with the different risks, etc. I can implement this for almost nothing (I have to buy a 240v contactor, which is HVACs name for a relay, and is about $20), but I have everything else, and if it doesn’t work, I can take it back off easily.
Anyway…
If I could buy the Aquanta software without having to buy their hardware, I think that would be ideal in my case. But, they are a packaged system, which I get.
SO… back to the original question, which maybe I should have framed as a lightbulb control app or something. Anyone know of an app that makes scheduling a switch on/off easy with a somewhat complex schedule?
Well, you should know by now that you are going to get a broader scope of opinion than what you asked for with this Community.
But honestly, I think we're concerned that there MAY BE a cost to implement this. The consistant set point of 120F is a suggested low temp for a reason. It's hot enough to use and hot enough to thwart health issues.
Addendum: I will admit, I don't think I have ever read of a family having health problems because of this. And the timer is a tempting idea. But here is the supposed thresholds of concern based on research. I guess the biggest susceptibility would be to someone with a compromised respiratory system breathing in bacteria carrying mist during a shower. Real risk or overdone?
""It is at these lower temperature ranges of 95 degrees to 115 degrees Fahrenheit that Legionella bacteria multiply and become established inside a water heater, says Corro-Protect. A study by the American Society of Sanitary Engineering showed that the bacteria cease to multiply when water temperature reaches 120 degrees. They are not destroyed at that temperature, however, and can survive to be conveyed to an outlet such as a shower head or faucet.""
Before I automated this, I would first insulate the drain and relief valves, wrap an insulating blanket around it, insulate the first couple feet of hot & cold piping, and set it to the lowest temperature setting that still provided enough hot water during a typical high demand. Regardless of anything else you do, these will give you the best bang for your buck.
After that I would start to save up for a tankless water heater. I'm not sure you get any "smarter" than that.
The "savings" math is not there for tankless systems. If you want convenience of endless instant hot water, then tankless is the way to go, but you will never recoup "savings" from going to tankless.
From what I understand that is very true for electric instant. I think I remember reading that gas tankless is far more energy efficient (again I'd have to dig that out and I'm not sure I'm right)
Gas does make the difference on these. Gas tankless can play into being a reasonable "pre-heat" stage for a electric water heater which then wouldn't have to work as hard and would act more like storage.
And there was a day where "whole house hot water" off a tankless was not a good idea. Things evolved. But STILL, it's a higher maintenance item than a hot water heater.
Every time these discussions come up on efficiency and savings I am reminded of a friend's black box solar water heater that when exposed to sun in a moderate winter (w/o snow cover) would make his hot water so hot it had to circulate through the hot water heater inside before it was "cool enough to use".
So much free energy if we just spent some time perfecting and commercializing those solutions.
Not even gas. Not to mention the 2x-3x times the price for the unit itself or the high install costs for having to run much larger gas lines to accomodate the 200k btu water heater, but just the usage itself. Say propane (since you can actually purchase this fuel at off peak times of the year) for easy estimation for every gallon of porpane produces 91,200 btu's. So for every hour the 200k btu water heater runs consumes about 2.2 gallons at an average (off peak) cost of $2 per gallon. That's $4.40 per hour of usage.
According to the graphs posted above from Aquanta, my electric dumb heater most expensive month this last year used 107kWh for the entrie month my current electricity rate is .10225 per kWh, that's $10.94 cost for the entire month or 36 cents per day.
That would only allow a total of 2.5 hours of usage for the entire month on a tankless system.
It's always been cheaper. Propane you can purchase your entire winter consumption (and sometimes yearly consumption depending on the size of your tank) in August one time per year during off peak pricing.
Natural gas winter pricing increases drastically just like electricity in the summer and you have no choice in the matter at what the price will be when used.
Last Februrary's winter storm highlighted this when the shortage occurred with many seeing natural gas bills in the thousands of dollars for that month.
Even hypothetically if nat gas was HALF the price of propane it still would not be "savings" over dumb electric water heaters.
Well, you should know by now that you are going to get a broader scope of opinion than what you asked for with this Community. 
