Water heater timer?


#1

Hi all, reading through here got me to thinking. My electric water heater is about 10% of total usage (not unusual); however, it does come on at 1 a.m., 4 a.m., etc. I know there are ‘smart water heaters’ that cost a bomb; but I’d rather not replace it if possible at this time. Can anyone recommend a timer/smart device to add on to a heater? Share your experiences here? Thanks.


#2

I have two 50 gallon electric water heaters in my house. They have both been under z-wave control for the last 2 years. I turn on the water heater for the upstairs only when I have guests visiting. I turn on the downstairs water heater for 45 minutes every morning just before I wake up.

I live in New Orleans; during the summer, the incoming water temperature is higher and the recovery time on the heaters is much lower - basically, they elements stop pulling current in about 20 minutes. In the winter, they pull current for 35-40 minutes.

Both my heaters have 4500 watt elements. In the summer, each heater uses between 1.5-2.0 kWh/day, and it is 2.8-3.3 kWh/day in the winter.

Has it saved money? I cannot tell because I had them under z-wave control before installing Sense. Also, at the same time that I put them under z-wave control, I put R15 jackets on the heaters and insulated the hot water piping. I think it is likely that all these changes put together have decreased my electric usage by some amount - I can’t give you a precise amount.

The other changes that I have made in the house were HVAC related - added a small amount of attic insulation, ensure ducts were sealed, and added an in-duct blower that causes conditioned air to be distributed more evenly throughout the house. I have recorded my overall electricity use for the last several years:

2013: 15285 kWh
2014: 13946 kWh
2015: 14618 kWh
2016: 12045 kWh
2017: 11136 kWh

My suspicion is that the bulk of the reduction in 2016-2017 comes from improved HVAC performance. Some of it may also come from reduced electricity consumption by the water heaters. HVAC and water heater changes were made between Dec '15 - Mar '16.

Edit: I installed Sense in August of 2016 (after all this work was done).

Edit 2: I’ve seen others use this heavy duty z-wave appliance module from GE to control water heaters. I used this heavy duty contactor from ELK, whose coil is plugged into a Leviton z-wave outlet.


#3

I did an experiment a while back after replacing my zwave water heater control with the GE unit which provides kwh.

Having it set to heat from 5-6am and 5-6pm reduces consumption by about 2-3kwh per week (~42kwh vs. 45kwh), saving roughly… $15/yr or $150 over the life of your average water heater. Our Arizona location obviously skews things a little.

The zwave unit ran $160. For the convenience of being able to tie it into home automation (including voice control through Google home), and it’s worth it.


#4

GE has a z-wave 220 volt switch which you can use as a timer with your automation hub. On colder days I was using 1.3 KwH in stand by cost. I added reflective insulation and brought it down to 1.1. I have read reports that you can lower that to .7 with more insulation.

Using the timer function I’m not saving much as the heater catches up when it is turned on. Where this pays off is the ability to turn it off in this remote vacation home when it is vacant. Overall I would not bother if you are only using this application for saving standby costs.

Depending where you are in the world and where the tank is you can, potentially, save more with a simple tempering tank.


#5

This is exactly the information I have been looking for. Thank you!


#6

Agree. Too costly. No ROI.
I used a $40 contractor, driven by a Sylvania smart plug and set Wink to shut it off every night for about 9 hours. Given the data Sense provides, I think it’ll pay back in <2 years. Not bad for something simple.


#7

Your usage percentage wise is lower than mine. I am at about 16%. Mine comes on for 5-8 minutes every hour whether anyone draws got water or not. It will then come on for 10 to 39 minutes depending on whether it was laundry, a shower or dishes. My setup I though was raising my usage because I have my entire house on a recirculating on loop with a pump. It’s set that if the water drops in the pipes by 10 degrees to 125, the pump circulates hot water and then the tank and the lines all become 135 degrees. Essentially, my pipes are an extension of of storage by about 3.5 gallons. I turned off the loop and we didn’t have the instantaneous hot water for a few days to compare usage between on and off states. To my surprise they were almost exactly the same.
People that have a timer on your water heater are playing a very dangerous game along with those lowering their thermostats to 125 or lower. Legionella disease can and does kill, there were nine veterans killed by it at a VA hospital recently. It’s crazy that it’s the government giving us advice to lower those thermostats when they know about this problem. 122 legionella can multiply but doesn’t die. Even at 140 it takes 23 minutes to kill it. 135 strikes a balance point for me with very low risk as it does die in a longer timeframe but really does t use that much more electricity. Another point I should make is my pipes are insulated with the highest R value insulation available for 3/4” pipe, 7.1.
Added screenshot of a typical days isage


#8

Yours comes on 27 times a day? Yikes!

If I have no usage mine is on at best twice a day. Its a normal 50 gal heater with an insulation blanket on it. I cant believe that 2 inches of extra insulation makes that much difference.!


#9

That 2 inches of insulation isn’t doing that at all. Insulated here as well and my 50 gal water heater is in a hot garage in Phoenix. My water heater also goes on ~30 times a day.


#10

It may come on 27 times a day but it’s 24 times of 5 -6 minutes and the other few for showers and such. The average total daily runtime of an electric water heater is 3 hours a day. Even coming on so may times my daily runtime is averaging about that. I also have recirculation and my water heater is in the crawl space where temperatures can be just above freezing when outside temperatures are 0-20 degrees. Don’t have a blanket on mine yet but adding it after the plumbing inspection for the new water heater. I won’t be buying a ready made blanket at the low R-value isn’t what I’d like to have. Instead of a value of 5 I’ll ise R-13


#11

Do you mind telling your family size and total daily runtime of your water heater for comparison purposes? I’m in eastern Kentucky with a family of 4 and a 40 gallon 4500watt tank.
Electricity is cheaper here than most places
Mainly because it’s a customer owned cooperative. Our KWH rate for the level plan is $.08448. We can have tiered rates if we want but by my calculations, winter would cost me more. Come spring I may try it. I’ll be the first of their 25,000 customers.


#12

This is what my water heater looks like for one day with no usage. Frankly, it doesnt draw enough for me to worry about switching it to save money. If it were coming on tens of times a day, i’d start considering it.


#13

This is what mine looks like for an average day. Located in eastern Kentucky and it’s been cold.
Mine comes on about every hour for 5 minutes or sister at 135 too and bottom.