Water Heater Automation

Create an intelligent timer for my water heater to save energy and turn it off when I don’t need hot water for a while

I have a water heater connected to a recirculation pump. The setup had a manual switch so you can turn off the water heater e.g. when going on vacation. I wired a Aeon Labs Aeotec Z-Wave Micro Smart Energy Switch, 2nd Edition ( https://www.amazon.com/dp/B008VWAPU4/ref=cm_sw_r_udp_awd_FwGFtb1AE6MQPZMX ) Into the circuit. The manual switch is now also connected to the aeon swith. I used the smartthings dashboard to turn off the water heater during the day if nobody is home (=AWAY mode) and to turn on at 6pm before anyone gets home (if in AWAY mode). Right now I using IFTTT to also turn the heater off in the evening after going to bed and turn it on in the morning before I wake up with sufficient time for the water to get hot by the time I want to take my shower. I will have to wait a month or two to report back estimated savings from the gas bill.

Has anyone created a “scheduling” app with multiple on/off points dependent on modes? I can only find apps with one off and one on event.

Very cool idea to save some money. I wish my setup supported that.

Have you considered using multiple instances of the “once a day” or “sunrise/sunset” apps, with certain ones working only when the home is in a certain mode? It’s unwieldy, but it might get the job done better than IFTTT.

You made me think more about this… So I used the regular switch app; turn on at 6.39am, turn off at 11pm, turn off when everyone leaves the house (only between 7am and 9am - so it stays on during the weekend) and turn on when everyone gets back. No more ifttt. Thanks for the comment!

I currently have a intermatic pool timer on my water heater. Does a 240v appliance module exist, or do I need to kludge something with a relay?

Here is the link to the manufacturer’s web site of the switch/relay I used. It says that it works 90/260v

Thanks, but at 10 amps max, it’s about 20 amps too short. I am now looking at one of these but not sure it’s supported by SmartThings:

Check this out:

It looks like one switch will work.

Good news: I received my first gas bill after running my water heater timer for a month and it is about $15 (or 70%!!!) lower than the previous month. Since the only other thing we use had for in the summer is cooking, I attribute the saving to the timer. Total cost of the switch, cables, box, was about $50 - so I will break even after about 3 month!


For those interested, I’ve created an event-driven app that can be used for @pizzinini 's use case, and for many others - like:

  • turn on demand when bathroom door closes, off when it opens
  • demand when motion detected near the kitchen sink
  • demand when the laundry room light is switched on
  • demand when a pocket door starts moving (I have pocket doors on 2 of my bathrooms)
  • demand every XX minutes
  • DON’T demand if the return temperature (as read by any ST temperature sensor) is above a set temp

All only when the location is in “Home” mode (or whatever you desire). The idea being (of course) to run the recirculator just prior to when you need hot water.


And for those interested in this kind of thing, I highly recommend looking at RedyTemp recirculation systems.


Their basic unit can be installed to run until the return temperature (as measured by a stainless steel temp sensor installed in the water pipe) reaches a settable temperature. This one is partcularly money saving - you can keep your water hot, but stop pumping once the temperature is reached. I’ve mimicked this in my SmartApp, and added the ability to turn demand on when the temp falls below the target.


I just stumbled upon this little gem: http://www.gaswaterheatertimer.com/

Seems simple enough.

Sorry for the dead thread revival.

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Nice setup. For my Electric Water Heater I have a similar setup.
After a few attempts, this is my method for controlling my Water Heater.

GE Light Switch on the water heater
4in1 Motion Sensors in the BathRoom and Kitchen
HEM (Home Energy Monitor)

How it works:
Motion detected in the Bath or Kitchen - Water Heater switch turns on with a five minute OFF delay
HEM is set to 400 Watts below the max wattage of the water heater, when the wattage is below that, the water heater switch turns off. (Solar panels required this setting). HEM also has a high Wattage setting to prevent the heater from turning off too soon.
Timer: Switch turns on at 4:30am to heat water for morning use. Takes about 35 minutes.

How it works:
If someone is in the kitchen, the heater comes on, if hot water is being used, the heater will stay long enough to reheat the water that is used or shuts off 9 minutes after no motion is detected.
When the shower/bathtub/sinks or washer is in use, the heater is on and stays on until the heater reheats the water. (Hot/warm water use only)
Leave the house the heater is off.
Go on vacation or go to sleep the heater will turn on at 4:30 am, this makes sure there is hot water when I return/wake up, and do not have to wait for the water to heat up.

Result: The water heater is off for most of the day even if people are in the house. and only on for 35 minutes each day when on vacation.

Why I like this setup:
1: The water heater will turn on if someone is in front of the bathroom sink or tub or in the kitchen.
2: The water heater will only stay on long enough to reheat the water.
3: The HEM wattage settings takes into account high wattage devices. (Oven, Split system AC)
4: As long as there is power to the house, there is always ‘On Demand’ hot water.


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@killarblaze007 Which GE Light Switch switch did you use for your setup? Do I need a specific model? I have one of these at home and I was wondering if it was the same as the one you used.

I have an electric heater and I am interested in trying this solution.


The GE 12722 switch has a max power rating from ~600W for incandescent (1800W resistive) . It will depend on your heater but a typical electric water heater uses ~4,000W. Dependent on what safety is built into the switch it may still work but I would not advise.

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That’s the one I use.

I’ve been using this setup for about 18 months. The current programming has been in use about 6 months No problems and works like charm for me.

The water heater plugs into a 110V receptacle.The switch turns off/on the receptacle. The heater is 1300W. I had an electrician install the switch while he was installing a neutral for the micro switches on the ceiling fans. He seemed to think the switch would be OK for this type of use.

GE12722 Z-Wave Wireless Lighting Control On/Off Switch
Aeon Labs Aeotec Z-Wave Multi-Sensor (Not the newest model) 1 Bath / 2 Kitchen
Aeon Labs Aeotec Z-Wave Home Energy Meter, 2nd Edition (DSB28-ZWUS)
Vera 3 running firmware 1.5


If you have a normal high wattage heater, get a Aeotec Heavy Duty Switch. You’ll have to hardwire it in. If you’d like a physical decora style switch to control the heater, you can use a Linear WT00Z and then use ‘big switch’ or duncan’s accessory switch device type to pair the two directly (or use a minimote).

Recently added a spare Aeon Labs DSC18103-ZWUS micro switch into the config. Now I don’t have to worry about what the AC or washer is doing and can control ON/OFF functions based on the wattage reading directly from the water heater.

Please Note: This hardware configuration is based on what is in my house. I thought Pizzinini’s setup was interesting and posted mine. I didn’t really expect anyone would try to duplicate it without checking their own water heater specs/requirements first.
We tend not to use Gas or 240V water heaters where my house is. (Bermuda) - My apologizes for not being clear in my first post.

If you have a gas water heater timer, you can control your water heater with Z Wave or any other home automated device by using an appliance module to link you to your smart phone, tablet, computer or touch pad for your home system. You can get more information from the gas water heater timer website.

Just ordered my gas water heater timer pictured above. Its shipping out today and also ordered a new leviton appliance module to hook that sucker up to. Will be hard to measure my savings right now due to the furnace running but I hope that this does help since I plan to put the heater to sleep when no one is home and when we’re asleep.