# When should you shut off your hot water heater?



## pulldownclaw (Oct 28, 2008)

Hi,

I thought this would be the best forum for this, apologies if it's not.

I've got my electric hot water heater already set a little lower because we've got young kids (I think around 120*), but I've always wondered what's best to do when we go out of town for the weekend, turn it down or off?  It seems obvious to turn it off if we're gone longer than that, but maybe not?  

What do you do?  I know I don't like it when I forget to turn it back on and get up the next morning and get hit with that freezing water!   :ahhh:


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## Highbeam (Oct 28, 2008)

Leave it alone. The stand by loss on that modern water heater is minimal.


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## Redox (Oct 29, 2008)

Ditto!  If it were for an entire week, maybe turn it off, but for the weekend; let it ride...

Chris


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## pulldownclaw (Oct 29, 2008)

Thanks guys, I'm not schooled in the arcane arts of simple math and common sense, so I appreciate it.... %-P


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## Hansson (Oct 31, 2008)

My 14 gallons hot water heater has stand by loss 0.7 kwh in an 24-hour period.


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## burntime (Oct 31, 2008)

pulldownclaw said:
			
		

> Thanks guys, I'm not schooled in the arcane arts of simple math and common sense, so I appreciate it.... %-P



I like that!  Another is it will all come out with a bigger hammer or bleach!


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## jebatty (Nov 1, 2008)

Take a look at this and you may reduce your electric hot water cost by up to about 50% by using heat traps and and additional insulation.

https://www.hearth.com/econtent/index.php/forums/viewthread/17010/#184943


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## jebatty (Nov 2, 2008)

Without disagreeing about the truth of high temps kill bacteria, legionnaire's disease is almost exclusively an issue within the hospital, nursing home and institutional realm, and then only for the elderly or immune impaired. It is a non issue in the home. 

If you scan the sites on hot water heater energy conservation, govt, industry and even health sites, all say knock the temp down well below 140 for hot water in the home. The risk of burns to children and others from 140 or hotter water, plus energy waste, absolutely outweighs the highly dubious benefit of any possible protection against legionnaire's disease.

If you have a genuine concern about legionnaire's disease, never set foot in a hospital or nursing home. And then consider all the health care and other workers in these institutions who never contract the disease. Now judge the risk of at-home legionnaire's.


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## Redox (Nov 2, 2008)

Yeah, Legionella is an overrated risk in the home.  Yes, it's possible to get it off a shower head or even sink aerator, but very unlikely.  If you are that concerned about catching things from your water, you should probably be chlorinating it.  In every outbreak that I am aware of, there have been conditions in the water system that have aggravated the situation.  One hospital around here had a concrete lined storage tank that hadn't been opened and cleaned in decades.  Horizontal heat exchangers are also possible problems as sediment can collect in the bottom.  Standard practice in hospitals now is to generate 140F water in a vertical heat exchanger and mix it down to 110F with no storage.

Chris


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## axiom10 (Nov 3, 2008)

Our tank is on a timer. Comes on for one hour between 9:30 and 10:30pm. There's enough hot water from that 1 hour cycle each day for both me and my wife to have showers (yes, separate!) as well as our daily hand washing, etc. However, we don't have kids, so yeah, well, with kids it's going to be more difficult.

Our setup is great though; we very rarely run out of hot water and we do save $$. I think the key with the timer is to heat *just enough* water--no more, no less. Keep dialing back the time your water is heated until you get cold water, then dial it up slightly. Once you start heating more water than you will use on an average day, your savings are lost as you are paying for the convenience of having extra hot water "on call".


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## stockdoct (Nov 4, 2008)

but isn't the heat lost, lost inot the basement of your home?  the same heat which morphs into heat for warming the house?    although turning off the water-heater during your vacation sounds reasonable, doesn't it simply escalate (incrementally) the amount your furnace needs to heat your house while you're gone?  BTUs have to come from somewhere.....

It seems turning off your water-heater would be a good idea if you also turn your thermostat "way down"......  or in the summer , when you have to cool that wasted-water-heating heat with air conditioning, but for the 90% of the year otherwise, turning down your home thermostat seems to be a better idea than turning off you water heater.


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## Highbeam (Nov 4, 2008)

Stockdoct, the btus leaking from the water heater are expensive. Just as expensive as running an electric resistance heater which seems to be the most expensive method to heat your home. You would be better off burning your efficient NG furnace or electric heat pump to make space heating btus.


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## oconnor (Nov 4, 2008)

Highbeam said:
			
		

> Stockdoct, the btus leaking from the water heater are expensive. Just as expensive as running an electric resistance heater which seems to be the most expensive method to heat your home. You would be better off burning your efficient NG furnace or electric heat pump to make space heating btus.



True - if you have NG or a heat pump.  If you have oil, even a new oil install,  - electric resistance heating is about the same cost.

Speaking of costs, here is a site to look at - he figures switching his 80 gallon heater off for an 8.5 day vacation saves him $0.20.  Check out his math, and let me know what you think.


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## oconnor (Nov 10, 2008)

My bad - I just realized 6 days after I posted that the link did not work to the site where the calcuations are done - here it is:

http://www.leaningpinesoftware.com/hot_water_heater_vacation.shtml


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## Kansasplains (Nov 11, 2008)

Water heater heat loss will vary a lot and is directly related to how well your tank (and hot water pipes) is insulated.  While this doesn't directly answer your question, if you are ever in the market for a water heater, I would highly recommend the Marathon electric water heater by Rheem.  They have a poly tank that has a lifetime guarantee.  More on subject, mine was turned off and kept water hot for a whole week.  I probably won't be turning it off unless we're gone for several weeks.  You can read a full review on the Marathon in the Green Room by clicking here.
Brian


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## KevinM (Nov 11, 2008)

In the future they are going to be changing electricity rates in Ontario to be dependent on the time of day.  Does anyone know if anyone makes an intelligent electric hot water controller that would try to minimize heating during the expensive times which coincide with times you would use hot water.  At the simplest something that would set the temperature lower during different times of the day.  This would be combined with a mixing valve to get consistent water temperature at the tap.

Kevin.


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## Rob From Wisconsin (Nov 11, 2008)

pulldownclaw said:
			
		

> Hi,
> 
> I thought this would be the best forum for this, apologies if it's not.
> 
> ...



Have you checked into "Time of Use Savings" programs that are offered by many Electric Utilities.
If you have an electric hot water heater, you can save a lot of money on your monthly bill.
By putting our hot water heater on a timer, and setting it to run only when the Utility gives us the 
discount rate, we save anywhere from $30 - $50/month.

Also, yes, turning-off your hot water heater over the weekend would save you a bit of money.


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## oconnor (Nov 12, 2008)

pulldownclaw said:
			
		

> Hi,
> 
> ...Also, yes, turning-off your hot water heater over the weekend would save you a bit of money.



I don't think you save much - the heater will lose some heat - loses more heat when temp differential between water and air is higher, so it loses more heat earlier in the weekend, and less heat just before you return, but it loses some heat...

Then you come home, you switch it back on, and heat all that water back up again - all you saved is the integrated heat loss differential between the loss rate when the water is hottest and the loss rate when you return home - I think the guy in the link above is right - he saved $.80 over an eight day vacation.

That, and if the water heater is inside the envelope of the home, you didn't lose the heat, 'cause it went into your house - all you lost is the difference between the amount of electric heat you can buy for $.80 and the amount of your alternative heat source you can buy for $.80. If you heat with wood, looks to me like you saved 1 stick (.5 cu ft) if you paid $250 a cord for it.

Does this make sense?


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## gpcollen1 (Nov 13, 2008)

Redox said:
			
		

> Yeah, Legionella is an overrated risk in the home.  Yes, it's possible to get it off a shower head or even sink aerator, but very unlikely.  If you are that concerned about catching things from your water, you should probably be chlorinating it.  In every outbreak that I am aware of, there have been conditions in the water system that have aggravated the situation.  One hospital around here had a concrete lined storage tank that hadn't been opened and cleaned in decades.  Horizontal heat exchangers are also possible problems as sediment can collect in the bottom.  Standard practice in hospitals now is to generate 140F water in a vertical heat exchanger and mix it down to 110F with no storage.
> 
> Chris



You may be able to sell that to someone who hasn't had legionalla.  I have and can tell you that the entire month was not fun, especially in not knowing what was wrong with both my wife and I.  Symptoms running in and out - going and coming.  If it were not for here respiratory infection not clearing up, they would never have done the additional testing to find out that is was indeed Legionella - and then I tested postive.  Glad the kids were not affected - but probably b/c they don't have their face so close to the shower head.


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## dbjc364 (Nov 25, 2008)

With children- should be set at 120*. A timer seems to be the ticket too. Ours was set to come on at 5 am every morning-off at 10 am,/for showers and if I had to run dishwasher-thats plenty of time. On again at 5p.m. till 9 pm.again plenty of time. off all night-saving us 8 hrs of heating water. It shaved off at least $20 each month and there wasnt any inconveinence. Time for a new one, as ours broke-yard sale item..also wrapping it helps alot.


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## Redox (Nov 25, 2008)

dbjc364 said:
			
		

> With children- should be set at 120*. A timer seems to be the ticket too. Ours was set to come on at 5 am every morning-off at 10 am,/for showers and if I had to run dishwasher-thats plenty of time. On again at 5p.m. till 9 pm.again plenty of time. off all night-saving us 8 hrs of heating water. It shaved off at least $20 each month and there wasnt any inconveinence. Time for a new one, as ours broke-yard sale item..also wrapping it helps alot.



... unless you are being billed for electricity by time-of use.  Those happen to be the peak hours and it would be better to fire it up at night instead.

Our TOU peak period in the winter is 7AM to 11AM and 5PM to 9 PM.  

Chris


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## jimcooncat (Dec 8, 2008)

We're paying 15.8 cents per kilowatt hour. Doesn't matter what time of day it is.

I wish we had non-peak hours -- yes, we'd do it differently.

http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_a.html


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