Water Heater On or Off?

[Blue Thunder]

At this point in the season, many of us are just doing weekends. I usually turn off the hot water heater on Sunday afternoon/evening when we leave and turn it back on upon returning Friday evening. Is this the most efficient way of doing things? What are others doing in this situation? Mine is a 40 gallon electric unit about 5 years old. Thoughts and opinions welcome!

BT

[brk-lnt]

The most efficient way is to turn the water heater off if you're going to be gone more than a couple of days. No sense in heating the water continuously while you're gone (and even if you're not using it, the water heater isn't a perfect insulator, so the heated water cools and then gets re-heated over and over).

We usually turn off the main water valve as well, just as a precaution.

[Old Hubbard Rd]

We do the exact same thing as brk-lnt. I turn the hot water heater on when we arrive and shut it off when we leave. I also turn the water main off.

[robmac]

I changed mine to a tankless unit,only comes on when hot water is needed.

[Dr. Green]

Most efficient (in terms of cost)...(in long run) - Solar Hot water
Next most efficient - natural gas Tankless Hot Water (THW)
Next - Propane THW
Next - Electric THW
Next - Oil tank
Last - Electric tank
The above is based on regular use. On occasional use on an island it might be different... but solar should supply all your hot water needs from April - Oct, so I think it would be cheaper just for the summer to.

Note - if you are on an island and getting solar - get flatplate, not evacuated tube. While the evacuated tube system is significantly better in winter - for three season or less, flatplate will work fine, and costs a LOT less.

www.sustainabilitynh.com

[Loony Singer]

Yep. We shut down the hot water circuit whenever we're gone, too. We have a SuperStor tank that works as a separate zone off the boiler, and I just put a simple on/off switch in the line from the tank's thermostat. Works like a charm. We're also surprised at how quickly the hot water comes back up to temperature when we switch it back on. Even in winter, we can enjoy a nice hot shower within 45 minutes of arriving.

We also turn off the main water line whenever we leave for more than a day or two. BUT...we put the valve in the line AFTER the line for the make-up water going to the boiler. I had a friend who didn't do this. He evidently had a small leak somewhere in his system, and ended up destroying his furnace by running it when dry.

[Island Girl]

I have a picture hanging over the electric box. If the picture is on the chair, the hot water has been turned off. If the picture is back on the wall, the heater is on!

Now if I could only remember to turn the water off, or find my sunglasses, cell phone and all the other stuff I have to go back for after leaving the island!

IG

[upthesaukee]

Originally Posted by Island Girl

I have a picture hanging over the electric box. If the picture is on the chair, the hot water has been turned off. If the picture is back on the wall, the heater is on!

Now if I could only remember to turn the water off, or find my sunglasses, cell phone and all the other stuff I have to go back for after leaving the island!

IG

How about taking a picture of your sunglasses, cell phone, and pocketbook and hang that at the dock? Sorry IG, couldn't resist it. I'm off topic, back to your regular program.

[SteveA]

Originally Posted by Island Girl

Now if I could only remember to turn the water off, or find my sunglasses, cell phone and all the other stuff I have to go back for after leaving the island! IG

I know how that feels!

This is a good graphic of the process. I also promise to get right back on thread.... if I remember.

[Island Girl]

I just might take that picture... I tried putting a little card in my pocket and several other places with the list of things to remember, but I lost them.

Thanks for the diagram Steve... looks a lot like my life!

IG

[Rattlesnake Guy]

Hot water off.
Pump off. ( to limit the disaster if a something breaks)

I used to have a list of things to remember...I lost it....I think.

The thing we forget the most is leaving the ceiling fan on. It is above our line of sight.

[Blue Thunder]

OK so the score is 5 for turning it off and 0 for leaving it on, and I think 3 for thread hijacking. I really thought at least someone would go the other way. Have you ever gone out and watched your electric meter spin off the house when you turn on the 220V to the water heater? It takes a considerable amount of time (hours) and energy to heat the cold water in the tank. Once it is hot and not being used I would think it would take much less energy to occasionally turn on the one element. Kind of like the theory that turning your lights on and off at night when you enter a room actually uses more energy than leaving it on. I guess I'll take my bat and ball and go home now......

Thanks everyone....

BT

[AC2717]

It is energy efficient to turn it off, but can be bad. When the water is heating to the point of getting it hot enough to shower in or whatever, and then cooled down, bacteria can grow in it and then it would need to be boiled to kill the bacteria, which the water heater does not get that hot. So if you are shutting the water heater off for a week it is best to let the water heat up and then run it for a whilte, then you are looking at being inefficient, best to do is turn the dial down but not off, if you have an electric one, it would be your call cause then you are wasting water to clear out the tank.

How do I know this, a cousin of mine got legioneers disease from just showering with a open cut/soar on his arm.

Side note, I turn the water main off to the cottage, I know there is nothing wrong with my water lines, but I like the piece of mind when I leave for a week or sometimes two, that I will not be coming back to a giant aquarium

[ishoot308]

When I had a hot water tank (I am tankless now) it was hot water off and pump off for the reasons noted in RG's post.

Dan

[Steveo]

My breaker box is in a bedroom. I painted two breakers white so that I can see them without lights on. It's also easier to explain to my wife what to do if I just say turn the white ones off. One breaker is for the water tank and other is power to the boat house. We draw water from the lake and the pump is in the boat house. I throw both breakers if I leave for more than a few days. My neighbor left his pump on, had a leak and it ran and flooded his whole downstairs for a week

[jmen24]

Originally Posted by Blue Thunder

OK so the score is 5 for turning it off and 0 for leaving it on, and I think 3 for thread hijacking. I really thought at least someone would go the other way. Have you ever gone out and watched your electric meter spin off the house when you turn on the 220V to the water heater? It takes a considerable amount of time (hours) and energy to heat the cold water in the tank. Once it is hot and not being used I would think it would take much less energy to occasionally turn on the one element. Kind of like the theory that turning your lights on and off at night when you enter a room actually uses more energy than leaving it on. I guess I'll take my bat and ball and go home now......

Thanks everyone....

BT

You are correct, it takes less energy to maintain the heat than to bring it back every week. The unfortunate thing and being on an island compounds this, is you have to keep everything on. Otherwise you run the risk of burning out an element in the tank if you turn off the water and get some draw down. Unless you can have someone stop by and check things out while you are away, keep it off.

It costs less money to heat the water than it does to remodel the home after a water line bursts in the living area of the home. Insurance does not pay for all of it, at least the six or so that I have worked on didn't.

Another thing for folks to keep in mind that shut down the heating system. If you have a circulator pump and do not turn the electricity to this item off, you run a high risk of burning out the pump if for any reason it calls for service. It can also become airbound, which makes life fun when you want heat after turning everything back on.

[jmen24]

Originally Posted by Dr. Green

Most efficient (in terms of cost)...(in long run) - Solar Hot water
Next most efficient - natural gas Tankless Hot Water (THW)
Next - Propane THW
Next - Electric THW
Next - Oil tank
Last - Electric tank
The above is based on regular use. On occasional use on an island it might be different... but solar should supply all your hot water needs from April - Oct, so I think it would be cheaper just for the summer to.

Note - if you are on an island and getting solar - get flatplate, not evacuated tube. While the evacuated tube system is significantly better in winter - for three season or less, flatplate will work fine, and costs a LOT less.

www.sustainabilitynh.com

Dr. Green, can you provide a break even time line for each of the items in your list. Not looking for the upsell, but the real honest to truth time frame for a break even point. Every application is different so something straight across the board that will keep things even would be great.

I will take the info in a PM if you do not want to post it. I am in the remodeling industry and this information is for my files if that helps.


As an aside:
One of our employee's has a solar water heating system on his home and uses it for heat in the winter than changes for domestic water in the warmer months. System is two years old and works great. Starting to take a look at adding geothermal for storage and eliminating the 2-300gal stone lined tanks. System works off ambient temp and is tied to a radiant heat loop. Payback on this system is estimated at 14 years and that mostly covers materials with some light sub-contractor costs. Keep in mind that includes the radiant loop material that would be required even if just tied to a boiler. 3500sf of heating space.

[Mee-n-Mac]

Originally Posted by jmen24

You are correct, it takes less energy to maintain the heat than to bring it back every week.

I disagree. I think it's less $$ and less energy to turn the heater off and then reheat each weekend. Here's why. The rate of heat loss from anything is proportional to the temperature difference. To maintain 140 F water when it's, say 50F out, will take a certain amount of Btu/day, that amount can be very low with a well insulated tank or perhaps "high" with a not so well insulated tank. But if you maintain water at 140 F and it's 50 F out, it's a constant loss and thus a constant heat input needed. If you shut off the heat input, the water drops to 130 F and looses heat slower than it would have at 140 F. As more heat goes out the temp drops even more and the loss rate slows even more. Maybe your tank reaches ambient temperature or maybe it doesn't, but the heat loss per unit of time is less then it would be at the higher, maintained temperature. If your tank reaches ambient then the amount of heat/energy needed to maintain that "high" temperature would have exceeded that needed to reheat back to that "high" temperature. It's no different in concept that trying to keep a leaky bucket full.

The question is whether you really want to turn the heater off. Sure it saves energy and thus $$s; we turn ours down to "vacation temp" when we're not up. But I read last year that the various Health Depts don't recommend this. They recommend that standing water be maintained at no less than 140 F (I think that was the #) to prevent the possibility of Legionnaires disease. Now we've never had an issue in all the years we've being doing this nor have I heard of anyone I know coming down with Legionnaires so maybe it's one in a million chance, I don't know, but it's food for thought.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/

http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_7.html

[jmen24]

Originally Posted by Mee-n-Mac

I disagree. I think it's less $$ and less energy to turn the heater off and then reheat each weekend. Here's why. The rate of heat loss from anything is proportional to the temperature difference. To maintain 140 F water when it's, say 50F out, will take a certain amount of Btu/day, that amount can be very low with a well insulated tank or perhaps "high" with a not so well insulated tank. But if you maintain water at 140 F and it's 50 F out, it's a constant loss and thus a constant heat input needed. If you shut off the heat input, the water drops to 130 F and looses heat slower than it would have at 140 F. As more heat goes out the temp drops even more and the loss rate slows even more. Maybe your tank reaches ambient temperature or maybe it doesn't, but the heat loss per unit of time is less then it would be at the higher, maintained temperature. If your tank reaches ambient then the amount of heat/energy needed to maintain that "high" temperature would have exceeded that needed to reheat back to that "high" temperature. It's no different in concept that trying to keep a leaky bucket full.

The question is whether you really want to turn the heater off. Sure it saves energy and thus $$s; we turn ours down to "vacation temp" when we're not up. But I read last year that the various Health Depts don't recommend this. They recommend that standing water be maintained at no less than 140 F (I think that was the #) to prevent the possibility of Legionnaires disease. Now we've never had an issue in all the years we've being doing this nor have I heard of anyone I know coming down with Legionnaires so maybe it's one in a million chance, I don't know, but it's food for thought.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/

http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_7.html

Well, it would be quite hard for me to argue with that point as it is a very good one. Thank you.

A couple of things that may play, but are unknown to us. The insulating quality of the tank and the temp the water is being stored at. Code tells us that output water temp cannot exceed 120 degrees F. Now being a homeowner, you can adjust that higher or lower depending on what you want, but we do not know if this was a DIY or a pro install or an adjustment after the fact.

At some point I would very much like to verify this discussion, it has been had before. I will agree that the quality of the insulation is the #1 variable in the equation. I just find it hard to believe that having the element run for a constant amount of time to heat the water back from room temp (at best, well water will enter at 55 degrees) as compared to giving a slight bump every hour or two. Maybe that 20 degree difference in storage temp would make a bigger difference in the long. Maybe the difference is less than I think.

I have not heard the temp requirement for Legionnaires, but have heard of not exceeding 6 inches with a dead end run. Anything beyond that does not allow for circulation of water within the stub end.

[Lucky1]

Water heater turned off when not there and pump turned off too. The circuit breaker box has room to pencil in the ones to turn off different areas.

Does anyone know how I find out where to turn off the hot water without such a marking? I have a handle to the house here that shuts off the water but do not see anything that tells me what circuit is the hot water heater in this house? How would I find that?

Put in some sod Friday in a berm area and came back here for Mother's Day. Is it frost there at night? Will it hurt the sod if it is? I can go back tomorrow or could go up and down again if necessary today. It is about two hours each way. Thanks if you answer.

[SIKSUKR]

There is NO way it can cost less to leave a hot water heater on.I don't care how insulated the tank is,there will be a heat loss.You will have measurable savings shutting down a heater during the week.My skihouse has an electric 40 gallon and we have hot water in less than 1/2 hour in a house that is set at 50 degrees when vacant.

[jmen24]

Someone has done the work for us.

http://www.leaningpinesoftware.com/h...vacation.shtml

The math and formulas seem correct to me, but other smart folks on here as well, so review and report.

Huge savings indeed

But it should be noted that it does in fact cost less to turn the water heater off when not at home. That will put an end to that arguement by me. Found more information than this, but the site above broke it out into the easiest to read terms.

The last paragraph should also be read for a FYI stand point, just brings another concern to the table.

[jeffk]

As far as I know it doesn't take any more energy to heat cold vs hot water a degree of temperature. So consider the energy required to heat the water from room temp to usable hot water as 100 units of energy (arbitrary measure). Say that the standing tank loses heat at 2 units an hour and if you left the tank on it would use two units of energy to replace what was lost.

Suppose you went away for a day and shut the tank off. It would cool down gradually and lose 48 units of energy (I am simplifying here, the loss would not be a steady rate). When you got back it would use 48 units of energy to bring the temp back up again. There is no significant difference between the energy used at 2 per hour or all 48 at once. So, even though there would be no savings there would be no loss either.

Now consider a longer period. At some point the tank would lose all 100 units of energy and assume room temp. At that point it will lose no more energy. If you left it on it would have continued to use 2 units an hour to maintain temp. If it was off, turning it on when you got back would simply require the 100 units to bring it back up to temp.

So in my mind, from purely an energy standpoint, you can't lose by shutting it off. At some point (a couple days?) you will start to save.

Someone mentioned watching the meter spin like crazy when starting up the tank. That's true but it doesn't matter. The meter spins because it is pumping all the 100 units into the tank rapidly BUT the cost of each individual unit is the same. If you are charged 3 cents per unit you are charged the same if the units are pumped in within a 30 minute recovery or they were pumped in gradually over the last two days. The issue is the amount of energy, not the speed at which is is delivered. The price per unit remains steady. Compare it to filling your car's gas tank. Are you charged differently if you slowly fill the tank vs. pumping it as fast as possible? No. The impressive speed of the numbers on the gas pump when pumping rapidly make no difference. All that matters is the final gallon total.

Also there is less wear and tear on the heating elements when you shut it off..

As to the health issues, I can't speak to that. I think that many, many people shut off their hot water and leave water standing in the tank without problems. I look at it as one of the struck by lightening issues of life, possible but very unlikely. If the tank has been standing for a long period of time it's probably not a bad idea to flush it before turning the heat source back on. I would think the same issue applies to the cold water tank so if you are concerned about this you need to flush your whole water system.

[Steveo]

Originally Posted by Lucky1

Water heater turned off when not there and pump turned off too. The circuit breaker box has room to pencil in the ones to turn off different areas.

Does anyone know how I find out where to turn off the hot water without such a marking? I have a handle to the house here that shuts off the water but do not see anything that tells me what circuit is the hot water heater in this house? How would I find that?

Two ways - first tanks usually make a low humming sound when heating (need to have your ear to it). Run your hot water until you hear heater turn on. Then cycle through your breakers until you hear it stop. Breakers could be single or double (120 vs 240) and more than likely be 30 amps. The second way is to carefully remove the plate that the power supply wire goes into your tank. Hook up simple power tester light (couple bucks at hardware store). Then cycle through breakers until light goes out.

Good luck

[Island Girl]

I looked at the link about all the math behind turning off the hot water heater. It looked like the assumption was that it was 60 degrees in the room in which the hot water heater was located. In my case, the heater is under the house, exposed to outside air temperatures. This week that can go down into the 30's. I would think the savings are much greater turning it off instead of the heater keeping the water at 120 degrees while we are not there.

IG

[Blue Thunder]

...for all of the posts. I knew someone on this forum would do the dirty work for me. Everyone's situation can be a bit different. In mine, it's not worth the effort to turn it off and not necessary either, so why bother?

BT

[jmen24]

Originally Posted by Island Girl

I looked at the link about all the math behind turning off the hot water heater. It looked like the assumption was that it was 60 degrees in the room in which the hot water heater was located. In my case, the heater is under the house, exposed to outside air temperatures. This week that can go down into the 30's. I would think the savings are much greater turning it off instead of the heater keeping the water at 120 degrees while we are not there.

IG

IG, I would agree. The math also takes into account the insulation value of the tank itself. These are all things that will raise or lower how much you could save.

Although you cannot use just any old insulation laying around, they do have fiberglass insulation products that you could wrap the existing tank with. That would increase the R-value of the appliance. The product has a grey vapor barrier attached that feels more like a plastic material than the tradition paper backed fiberglass batt insulation.

Doing this will help keep the water in the tank, hotter, longer when it is running.

[SIKSUKR]

Originally Posted by Blue Thunder

... In mine, it's not worth the effort to turn it off and not necessary either, so why bother?
BT

I'm confused. Why did you ask the question? It's not worth the effort to flip a switch? Is the switch on the roof or something? With an electric wh not used all week you could save you $100 over a year. If still don't want to put the effort into flipping a switch then you could put a timer for around $30-40 and pay for that in one year.

[Mee-n-Mac]

Originally Posted by Lucky1

Water heater turned off when not there and pump turned off too. The circuit breaker box has room to pencil in the ones to turn off different areas.

Does anyone know how I find out where to turn off the hot water without such a marking? I have a handle to the house here that shuts off the water but do not see anything that tells me what circuit is the hot water heater in this house? How would I find that?

Originally Posted by Steveo

Two ways - first tanks usually make a low humming sound when heating (need to have your ear to it). Run your hot water until you hear heater turn on. Then cycle through your breakers until you hear it stop. Breakers could be single or double (120 vs 240) and more than likely be 30 amps. The second way is to carefully remove the plate that the power supply wire goes into your tank. Hook up simple power tester light (couple bucks at hardware store). Then cycle through breakers until light goes out.

Good luck

Rather than opening up the panel on your heater to get at the connections, go to Sears (or perhaps your local hardware store or Lowes or Home Depot or ?) and get an AC voltage detector for about $15. These devices detect the presence of the AC line voltage without having to make physical or electrical contact and beep/buzz to alert you. Hold the tip one near the heaters input AC line and hear it beep. Turn off the breakers one by one, checking between each switching to see if the alert remains or not. When you don't hear the alert, the last breaker opened was/is the heater breaker. Turn that breaker back on and make sure the detector beeps again. You've found your breaker, label it. It'll usually be a dual breaker BTW.


Link to Sears Tester

[Lucky1]

Many thanks Steveo and Mee- n- Mac. Will do my best to find the right circuit breaker. Personally do not like having to keep the hot water tank heated when not here.

Here is a shocker...........the lake house has a 1979 hot water tank!! Am afraid to change it since we have had several hot water tanks replaced at other locations! One is a condo though so for the building it would not be fair to have a tank go. In the cottage there is just a cement floor in the utility room with a turned off water pump so there would be water I guess but hopefully not cause a lot of problems if it went when no one was there.

[Blue Thunder]

Originally Posted by SIKSUKR

I'm confused. Why did you ask the question? It's not worth the effort to flip a switch? Is the switch on the roof or something? With an electric wh not used all week you could save you $100 over a year. If still don't want to put the effort into flipping a switch then you could put a timer for around $30-40 and pay for that in one year.

Easy there Sik. My point is that if the savings between on or off is only 24 cents on an 80 gallon electric unit over the 8.5 day example given then my 40 gallon unit is probably something less than that. For the 20 or so weeks that I would consider turning it off, I would save a total of $4.80 for the year. THAT is why I asked the question.

BT

[Rattlesnake Guy]

We added this device to our breaker panel to indicate when the tank is heating. That way you can wait till the light is out to maximize your hot shower experience after your teen takes one. The LED runs off the sensed current by running the ac leg through the ring.

http://www.crmagnetics.com/products/...tPDFs/2550.pdf