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Craig Muccio

About "Ask the Energy Expert"

Craig Muccio runs FPL's Conservation Research & Development Program and crunches the numbers to figure out how you can save by managing your energy use.

Your questions on energy-related topics can be submitted anytime to our Ask the Energy Expert blog. Just click here to submit your question, and if chosen, it will be answered here

Water heaters: Turn off or leave on?

By Craig Muccio

Asked on: April 30, 2015 by Frank L., FPLblog.com comment

Is it a good idea to turn off the hot water tank overnight or when not using it?

We turn off lights and other things when we’re not using them. So, of course you’d wonder if you should do the same with your water heater. In fact, it was one of the top questions we received from customers following my recent post on the cost of heating water in your home. Because there was so much interest, we wanted to talk a little more about water heaters this month.

Savings from turning off water heater
Turning off your water heater when you don’t need it could help you save a few bucks each month if you have a tank-style heater that’s standard in many homes or even one of the newer hybrid, or heat pump, systems. That’s because even though water heaters are well insulated, a small amount of heat does escape the tank while hot water is waiting for you to use it. That energy loss is typically about 10 percent. So, for an average FPL customer which we estimate spends a little under $20 every month to heat water, about $2 of that cost is due to heat loss. That’s money that you could save by turning off your water heater when you’re not using it.

And, you may be wondering if you’ll end up using more energy to heat water that’s cool because you’ve turned off the heater. Not really. Think of it this way -- you’re paying to heat the water anyway, regardless of whether you heat it right before you use it or heat it and let it sit until your next use. The small cost savings comes from avoiding the escaped heat while it’s waiting for you to use it.

The “how to”
Want to give this a try, but don’t know how? My colleague shows you how to turn off your water heater in this Ask the Energy Expert video

If your water heater has an on/off disconnect switch as shown in the video, we recommend turning on the water heater a half hour before you need it, giving the unit time to heat your water. Then, you should shut it off again just before you start using hot water. Why? Well, if you wait until after a shower, for example, to turn off your water heater, it will start heating the new water that fills the tank, leaving you with another full tank of hot water and the escaped heat situation that you’re trying to avoid.

I imagine some of you might worry that you’d run out of hot water if you turned off your water heater before hopping in the shower. Keep in mind, your tank has a certain amount of hot water available at one time, and once it’s used, it takes time to reheat the tank as new water is added. So, essentially, you can run out of hot water regardless of whether you leave the water heater on during your shower or turn it off. Tankless water heaters are the only option that can supply hot water instantaneously.

What about timers?
Of course, you don’t need to turn off your water heater manually. You could always consider automating this step with a timer. This may save you some time, but possibly not the money you’re hoping for. You’ll need to weigh the cost of buying a timer and installing it against the estimated $2 monthly energy savings you could get from turning off your water heater manually.

More information
Have a water heater question I haven’t answered? I sincerely wish I could answer every question we get! Here are some additional resources that may help you find what you need:

 U.S. Department of Energy

FPL Energy Experts

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Comments [91]

  1. Cindy

    If it costs $20 to leave the water heater on 24 hours a day and to save money the water heater is turned on 4 hours a day(2 hours in AM & 2 hours in PM), then wouldn't the savings be closer to $10 not $2. If you are on the 'on call' program, then you may have the situation of turning on your water heater but the 'on call' device keeping it off. I had 2 experiences with such devices as left overs from previous occupants. The first device was removed because it was hard wired in and I couldn't shut off the water heater. The water heater was indoors and I would heat it for 1 hour every other day because the water would stay hot enough for a single person's 2nd shower(just used less cold water), saved money on A/C & heating the water. The second device had a setting to shut off the water heater so I kept it attached and used the device's shut off. There was never a time where the 'on call' device kept the water heater off when I turned it on, probably due to my tendency for morning showers and not during peak electrical usage times(afternoon). I think it voids the 'on call' discount if the device is disconnected by shutting the water heater off at the breaker. I currently don't have an 'on call' device because I didn't think about it until now. I just looked up my address and would get $18 a year credit for water heater enrollment which makes me wonder if the credit would pay for the electric usage of the device.

  2. Henry Chapman

    Should I turn off my water heater when I'm in Florida for the winter?

  3. Dona Lee

    What about turning off a water heater for an extended amount of time? Many snowbirds leave their electric on to run the A/C to keep their homes from acquiring mold. If the water heater is left off, would it accumulate algae? How long can they be left off safely?

  4. Ted Vaughn

    I had solar water heater panels installed two years ago. At first I left my electric water heater on and saw no noticeable decrease in my electric bill. Last year, I turned off my electric water connection...and, I still see no reduction in my electric bill. What gives? By the way, I get plenty of hot water.

  5. Verl

    Just wanted to let you know that we have been shutting our water heater off for some time. It is easy for us. When FPL came out several years ago to install out on call system; I had an extra box , wiring & switch. I asked them to install this inline of the power supply & the water heater. I wanted this at the time so that when left for a couple weeks on vacation we would not have shut the water heater off at the breaker box. There are only two of us in the home. We shut off the water heater at the switch after the last person has bathed of a morning. Then we turn the switch on early morning. Usually during a early morning rest room visit. We have saved from about $3.00 to $13.00 per month by doing this.

  6. Larya Debow

    Do you recycle our old refrigerator and pay us for recycling them? MIchigan picks up free OLD refrigerator and we get $50 for doing it.

  7. Larry L Phelps

    Well I have found another way to save, If you have a modem you can turn it off at night and save a bundle, also take the battery out of the modem so that there are no lights on, and unplug your cable box also the Microwave unplug it until you need to use, anything that has a light on you will be surprise at the amount of Elec. they use.

  8. Dale Cornelissen

    When I leave my seasonal home in Florida, I shut the power off on the water heater. When I come back in the Fall, I turn it on but the water smells like rotten eggs.. I end up draining the entire tank and starting over. Why does this happen and what can I do to avoid all this work?

  9. MICHAEL D MAY

    Yes, I open the circuit breaker for my water heater during summer. The water heater is in my garage and it maintains high temperature during the summer. Sometimes the water is cool - but at 92F in my garage, that's not too bad.

  10. David Van Brunt

    I am a house watcher in a large community taking care of people's homes while they are away for up to six months. I attended a Property Management Seminar provided by University Of Fl Extension Service. They addressed the issue of turning off gas fired tank type hot water heaters. I recognize you are addressing electric heaters. However, they recommend NOT turning the unit completely off during extended absences because mold will form in the top of the tank that is void of water. Leaving the pilot burning provides enough heat to prevent mold. I suspect they would have the same comment about electric water heaters, to turn them all the way down to the lowest setting. Have you done any research on this possibility of mold formation? I thought mold would need some sunlight to form, but apparently not. David Van Brunt 941.400.5624

  11. Ms Gene D Sims

    Thank you for the information on shutting off the water heater when it's not in use. I appreciate the info and will comply. Thanks again.

  12. uppercase Q

    Does it have to lose heat? Suppose you take the water heater out in space. There is no matter to conduct heat from it. How does it lose heat? Answer - IR. Ok, then is there a way to reflect IR? Answer - Some of it. Aluminum Foil. etc., etc. Let me jump to the ultimate question? Is there a way to reflect all of the energy from a Gamma Ray Burst?

  13. bernie

    If I am not in NY all winter to be in Fl. should I shut down the water heater? Will it freeze when temp. drops? Is it safe to turn it off when I leave for Fl?

  14. Sterlin Sinevet

    I need ways to save on my electric bills

  15. Hilarion Cabrisas DR

    Question regarding TITAN water heaters: Seems like that question has not been answered: Is it better to turn those off or keep them on, what gives least usage cost???

  16. Phil Davis

    I live in Century Village East,and my water heater is under my kithchen counter ,only accesible if aI move my stove. how can I install a manual switsh?, or do I have to use the BREAKER to turn it off & on.?? Will it cost me more to do this installation, than I will save on my bill? Please advise. Thank You, Phil Davis

  17. Joel gorelick

    What are the steps in draining a water heater

  18. Gillian Kendall

    Good article. I have a hot water heater that's very hard to access. What would a timer cost? Who would install it?

  19. Steve Auman

    My energy usage and consumption is way up for the last 2 months over last year. We practice energy conservation and we have the same number of people in our household with the same daily routines. I realize weather has a lot to do with it, but my billings are up 70-90.00 over last year. Are others in my neighborhood experiencing the same rise in consumption?

  20. norm

    we tried the turn off when not in use and back on 1/2 hr before needed, we came to the conclusion this was a bad idea, the tank rotted out in less than 1 year on a brand new tank. the theory is that as the tank heats up it also expands, when it does this the fresh layer of rust flakes off leaving fresh metal to rust again, so the expansion and contraction from heating and cooling causes a very rapid rust out. now this wouldn't be a problem if the tank was made of stainless steel.

  21. Marlee swales

    Turn off the hot water heater at heater or inside , at the fuse box?

  22. _Pauline Lyn

    What about a Tankless Water Heater? Is it better to turn it off overnight or when not in use?

  23. Jan Dudding

    Why do you need to turn your water heater off if the electricity is off?

  24. Curtis Houk

    About systematically shutting off the home water heater during periods of non-use.. We installed a timer and started using this practice to conserve energy - as your 4/30/15 article suggests- but noticed that each day we would accumulate air in our water lines. I am assuming it is because the fluctuation in temperature results in varying gas solubility (if I remember my chemistry). Besides the little bit of nuisance from spitting faucets, I am concerned that this daily collection of air in the home piping network will result in increased levels of corrosion or scale. Any thoughts?

  25. Matthew Shalette

    My hot water comes from my gas boiler that makes hot water to circulate for heat. Can I still turn off my hot water tank? Hoow would I do that?

  26. Libby Coates

    My bill was almost $700.00 a month. It was over $2000.00 in 4 months. I tried to get help several times. When I called I was told that I was using that much electricity. I finally found the problem myself. My hot water was running constantly because of a broken pipe under the floor. I feel fpl should have sent someone to check out the problem. My bill is estimated at $275.00 next month. I feel that there was a problem for a few years. It finally broke about 4 months ago. I'm retired, it has been a real hardship.

  27. william

    this advice is much better than some given by FPL in the past, such as "don't turn off your AC when not home". depending on the size of the tank, and the number of the occupants, if they all leave for work in the morning, it might be a good idea to turn the unit off when you first get up, use up the hot water, and not turn it on again until you need it again when you return. this way you get the benefit of the heated water, but have no energy loss during the day. it may even be possible to just heat the tank once a day, and then turn it off until the next day. if possible, this may be the optimum practice

  28. Garru

    My FPL bill is always very high. This Month is $385. I have a pool, which the pump has to run about 8 hrs per day, and a sprinkler system I run on Mon, Wed, and Friday for 3-4 hrs. Any idea where I am using too much power, or area I should check?

  29. Ken Czarnecki

    When going north for the summer (8months)does it hurt to turn the power off at the electric box. Also do you recommend emptying the water from the water thank or leave full it has a terrible smell when you start it up until you run water for a while.

  30. Gloria Peale

    Will a water heater last longer by turning it off when hot water is not needed?

  31. Charles Carpenter

    As an addendum to the question...I have well water with high sulfur content. While away the same water stays in the tank. Is it better to turn it off and drain it than to leave it in the tanki?

  32. Roy Miller

    If you plan on turning your water heater on & off certain times of the day you need to either install or find in your system a common "on & off" switch. The circuit breaker in your switch box was not designed for this purpose. It's there if you want to work on wiring in your house or if the circuit gets overloaded on a particular leg of your wiring.

  33. Marie C. Volcy

    I believe that I had told the FPL Co. before to turn off the water heater system over night when is not being used to reduce the cost of energy. Although, I am not certain if there have been any changes but I am almost positive that's the way it should been set as we speak. If it hasn't been done then i would like to request the service as long there's no additional charges added to my bills. Thanks,

  34. jim

    is it ok to turn off hot water tank by turning off the circuit breaker switch?

  35. Dave and Anita Sprague

    I (Dave) saw a Porsche 911 at an autoshow in Naples 3 years back. It had been converted to run on battery and there was some indication it may have been done by someone affiliated with or employed by FPL. The specs were impressive but there was no one to speak with and no contact information. I am, at the least, very curious about how it was done. The placard on the windshield said the motor replaced the engine and the battery & charging equipment replaced the fuel system. It continued to use the transmission. Pretty simple. Are you aware of anything like this? Kind Regards, Dave Sprague

  36. timothy harris

    Do water heaters have an installation date on them somewhere? How long is the average life? Should they be drained? How often?

  37. Gordon

    for well over 50 years I have been managing electric Hot Water Systems from household to hotel size. In the house the HW heater is turned on only before hot water is required. Here in Florida this is quite acceptable however in the cold northern climes the stand-by mode is needed owing to the very low temperature of in-bound water. Lets just say that whatever and wherever, management is a good thing, automatic or manual. There is little sense wasting precious energy, and resources such as water. Here in south Florida turning the H.W. tank heater OFF is a good thing. Stand-by heating is wasteful and unnecessarily increases demand upon the grid. timers are best. set them up to 10 to 15 minute on, then off for an hour or two, then another short reheat in advance of the calculated demand hour(s). As stated, I simply turn on the breakers in advance of need, and off before using the warmed supply. There is little practical need of very hot water. Cool to warm is best for the body, not hot! Steamy hot showers are for the north, not here!

  38. Mary Lou Corey

    Why does it take a long time to warm the water by running it out of the spikot?

  39. Hyacinth Philp

    This sounds like good news what about my Air Conditioner Do I turn off if not at home or if tit is cool outside and only need a Fan. Thanks

  40. Herman R. Ouellette

    Emphasis should be stressed on NOT using the circuit breaker in lieu of a switch. In my 25 years of servicing appliances I observed this many times and had to instruct customers to have a proper switch installed. For those who wonder why, the circuit breaker will wear down under constant on/off operation and will lose its effectiveness as a safety device.

  41. Ellen Capezzera

    If you go on vacation and turn your water heater off should you also turn off the water in the house?

  42. John Davis

    Thanks for the info. What is the effect on water heater tank life due to temperature cycling due to turning the heater off and on? The temperature drop would be significant when the water heater is turned off for a week or more.

  43. Al

    Someone mentioned to me that turning it off will cause calcium to build up on the bottom. Can this be clarified, please. Thanks.

  44. maria

    I always turn my water heater for 3 days at a time.l don't use to much hot water take my shower cold love it.is to HOT now.

  45. steven gauci

    Hello, Why are you just saying hire a licenced contractor to install a shut off switch on your hot water heater! Big Bucks Here$$$ You never even talk about your switch on the breaker panel. It is the safest and easy way out with no cost whatsoever! Also your switch is made better than a cheap $ 1.15 switch that your pro would put in! Hello!

  46. Jean Madden

    Leaving for summer. Temperature of air conditioner? Unplug what things? Know to shut of water heater. Any other info would be appreciated. Jean

  47. Glenda Fraser

    I have been turning off my hot water heater for over a year now and only turning it on in the off hours when the grid is not busy. Before I shower I turn it off as there is plenty of hor water left and I know my tank maintains the heat for approx. 3 hours. Plenty of time to do any other chores.

  48. Roberta McKinley

    Great info!

  49. David A Roy

    I read your comment and found it to be very helpful,however,I have a solar system, Does this stand true for my system on shutting off the hot water tank?

  50. B. Reinking

    If one has a soft water salt conditioner system, does that salt water system shorten the life of the water heater? Thank you, Barbara Reinking

  51. Marcia

    I have on call with fpl. Should i still shut water heater off? Does it ever need checking or servicing?wecare in our townhome over 25 yrs its located in our crawl space under steps?

  52. Candy

    If I am going on vacation for 3 months - should I sht off my water heater at the breaker?

  53. John R Blasi

    Thanks for the overnight water heater tip. What is the advise for people who are snow birds and leave their Fla home for several moths over the summer. Should they turn off the water heater while they are away?

  54. d

    I turn off my tank type water heater when I don't use it and it saved 30$ a month .... def turn off when its not needed.

  55. Rpger Horst

    Appreciate the comments on how little you save by turning off the hot water heater. My question is regarding the actual equipment. Does turning the heater off create any possible equipment problems or does leaving it on create any possible equipment problems. If turning it off is the best solution do you recommend draining the heater.

  56. jim Snyder

    Great information. Very good for F P & l to help their customers save money and still enjoy good service. You are a great company, excellent service and customer friendly.

  57. Noel Vonkauffmann

    Gentlemen: As one of the originators of promoting and successfully marketing "water heater timers" and other now everyday energy-saving devices in this country, 40 years ago, I would like to add that your $2./monthly savings is on the low side of estimation. Being retired from electrical engineering design/marketing, my hobbies include testing tried and true theories. Typically here in south Florida there remain untold numbers of very old residences/condos/apartments not yet updated with efficient appliances and hvac systems, and I have performed a survey on a typical one BR/1bath apt. for tenants who have no clue about power savings. My best example with a 12-month test: By lowering the scalding heat setting 5 degrees and manually turning off the water heater for 2 days with 2 retired people who only take short showers, and by washing with cold water, plus not using the electric dishwasher, the estimated monthly savings has quadrupled. Couple this fact to having them change all light bulbs to CFL's, using the microwave more than the old stove, and raising the old round t-stat setting to 78-degrees, then the total average monthly savings in this case is the difference between $115./mo. and currently $45-$55./month. Think of the savings from larger residences.

  58. Larry Odom

    Last month the question was asked about what to do with the AC when the condo was vacant for a long period. That day I submitted a question to Ask The Expert regarding the fact that I had a humistat along with the AC thermostat and had no idea how to work them together when it's used everyday and when the condo is unoccupied for a period of time. I received no response and could not find anywhere the answer may be. If it was answered do you have any idea where I could find it? If it wasn't answered then forget it, I'll just wing it.

  59. anthony Di Salvo

    ? I have COLD AIR leaking out on both sides of my Condenser ie inside unit the unit was replaced 4 years ago, prior to me buying house. there is virtuly no room between unit and side walls. Any ideas thank you Anthony di salvo

  60. Jeanette

    When you are going to be away from a house for several months, 4 to 6 months, should you turn off your refrigerator? So many people say Yes, and just as many say No. What is the correct thing to do.

  61. Judith A. Gibson

    We are snowbirds. At what temperature should the thermostat be set when we leave for the north in the spring?

  62. linda Gray

    Should an electric hot water heater be periodically drained, especially if it will not be used for a few months?

  63. Tom Sharp

    Are there state or federal rebates for new air conditioners?

  64. Bob Frechette

    What about if you leave for 4 months. Does that hurt the heater more than it saves you money

  65. Juan Alfredo Vega

    What are the risks of developing bacteria or other organisms in the water tank if remains off for a long time?

  66. Anthony Molinaro

    does turning off water heater in a Florida condo have any correlation to the water heater bursting and flooding while I'm gone for 3 months this summer?

  67. carol marer

    my electric bill was well into the 100s I did other things but shut my water heater off and cut my bill in half so it worked for me I turn it on heats up pretty quickly so I think it works for me

  68. DENISE NIRO

    We are snowbirds and leave Florida for 8 appriox 8 months of the year. Do we still turn off water heater, and how do we know if the waer heater which is a RUUD is still good after 8 or so years. Thanks

  69. Joseph Startare

    Is it a good or bad idea to use the Shark Bite connectors when installing a replacement Hot Water Heater. Thanks for all your great suggestions and information Keep up the good work. Joe

  70. Marvin Bass

    I go north for 5 months at the end of May From what I HAVE READ IS IT ALRIGHT TO SHUT OFF MY HOT WATER HEATER for this period of time?

  71. janet

    when is the best time to run dishwasher? thank you Janet Cummings

  72. Linda Umansky

    Can you turn off your hot water heater if you have "on call?"

  73. Bill McKechnie

    They say that draining your water heater can add to the life of the heater. Is this true? What is the proper way to do it?

  74. Marlene preeper

    I am going away for 2 weeks should I shut of my water heater,if so will I save and around how much thank you

  75. Dan Cook

    Will turning off your hot water heater extend the life of the water heater?

  76. Lynn

    Hi Is it possible to get solar for hot water and electric on home ? Plus don't we get a credit if we got solar ? Cost approx ? Thank you

  77. Leslie

    I read the "Ask the Energy Expert" column about whether or not to turn off the water heater when it is not in use. I'd like to know if it's appropriate to turn it off at the breaker, rather than on the unit itself. My water heater is rather difficult to access. Thank You, Leslie

  78. Michele

    You can turn the heat down in the summer reducing gas, as the groundwater goes up like 20 degrees in Florida.

  79. Pat Brown

    Tha k you so very much for gbat answer .because i will do that.

  80. Ruthann Hess

    What tips should I do to save money when going on vacation.

  81. jim betterley

    Why does FPL continue to lie about rates going down while mine are sky rocketing? Your bills are outrageous and your service is terrible, everybody knows that. Please don't insult our intelligence anymore with your ridiculous claims. Be honest we can't do anything any way FPL padded enough pockets to make sure a good electric company will never come here, we're stuck with you...until we move.

  82. Harold Morrison

    thanks for your information on savings by turning off the water heater tank. How often should I drain the hot water tank to flush any sludge?

  83. Frank Shaw

    Is it a good idea to drain the hot water tank occasionally ?

  84. sharon sklar

    Our refrigerator is 2 years old. The manufacturer says to leave it on, even if you'll be away for an extended period of time. We are not in FL from May 5-Nov. 17. Is there enough of a savings from turning it off to offset the worry that it may not be good for the workings of the unit keeping it off for a long period?

  85. MAI PHAM

    i would like to ask a question :should i unplug all the appliances When i don't use them at night ( toaster, microwave ..) thank you

  86. Anthony

    when going on vacation, is it a good idea to turn off the water heater? Do you turn off the power and the water valve going to the water heater?

  87. Pinnetti

    i am on a budget account , why is the amount different every month ? I really need the same amount every month .

  88. Ellen

    Going away for the season. How expensive is it to leave the refrigerator freezer on

  89. joyce

    Do you have a kit that for free to wrap your water heater. CMP back home provided them to customers. Also do you think that a timer would cut some of my power bill. Joyce

  90. Leslie Boucher

    I do save on the water heater I just need to save a lot on all these condominium buildings outside lights give me a good answer to confirm the best lights to use I am a retire electronics engineer can I work for you?

  91. William Davison

    What does the "ON" setting on my huimidistat mean, what does it do, how doesit work. I have separate thermostat and himidistat.

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