Adjust Electric Water Heater Temperature (Step-by-Step Instructions)

January 19, 2009 | by Kim (email) |

Since I just had to do this for our adoption home inspection, I thought I’d post a step-by-step for anyone else who wants to change your hot water temperature.

Why Adjust Hot Water Temperature?

If you can stand shorter (or cooler) showers, turning down the thermostat on your water heater is a great way to save on your electric bill each month.  Also, according to the EERE, a lower hot water temperature reduces mineral build-up and slows corrosion of your hot water pipes.  That’s not why we did it, though.  We just wanted to make sure our faucet readings were well below the 120-degree upper-limit for an adoption inspection.

Note that setting your water heater temperature too high is dangerous, and can result in scalding.  Setting the temperature too low may reduce your dishwasher or washing machine’s cleaning power if they lack an internal heater.  A temperature between 120F and 125F is ideal for most situations.

Here’s general instructions for how to adjust an electric water heater’s thermostats (there are two, one at the bottom and one at the top).  Consult the owner’s manual that came with your water heater for instructions for your particular model.

Steps to Set Water Heater Temperature

THE TOOLS: You will need a phillips-head and a flat-head screwdriver.



STEP 1: CUT THE POWER – Before you do anything flip the breaker or pull the fuse to turn off the power supply to your water heater, so you don’t electrocute yourself!


STEP 2: LOCATE THE TWO THERMOSTAT COVERS – one at the top and one near the base of the water heater.  (In our picture, the two gray doors)






STEP 3: REMOVE THE COVERS – using the phillips-head screwdriver.  Save the screws in a safe place, since they’re tiny and easily lost.



STEP 4: REMOVE THE INSULATION behind each cover door to reveal the thermostat behind it.





STEP 5: READ THE EXISTING TEMPERATURE – The white triangle on the rotating dial points to a spot between two labeled temperature levels.




STEP 6: TURN THE DIAL to your desired temperature, using the flat-head screwdriver.









What do you think? What temperature is your water heater set to?  Have you adjusted it to save money?

26 Responses
  1. Todd says:

    Great post Kim. This method works for direct fired water heaters. If you live in a house with indirect water heaters you’ll need to adjust mixing valve from the boiler to the tank.

    Another note, some building codes require hot water to be a minimum of 124F at the faucet and 140F in the tank to prevent Legionnaires Disease.

    • Gladys says:

      How long does it take the water to cool down from 1:25 to 90 degrees what do you mean by second thermometer as usual I’m a woman I’m trying to learn

  2. Kim says:

    … and that’s why we have you! Thanks for adding that in, Todd!

  3. Todd says:

    Not a problem….the interesting thing is today most people are told to put their water to 120 F yet building code officials frown on it. It never fails that there are two camps out there offering us “safety” rules that never seem to align.

  4. Jon McDougal says:

    Shouldn’t you have a nice thermal wrap around that, to help conserve the heat and save on your power bill?

    It doesn’t get cold enough to do that down here.


  5. Kim says:

    Yes, we’ve been meaning to get a wrap. The water heater was new this past April and we just haven’t gotten to it. But it’s plenty cold enough here! (snowing as I type)

  6. Ethan says:

    Often newer water heaters don’t really benefit too much from a thermal wrap as they are so well insulated. I’d guess that wrapping your hot water heater won’t really save too much Kim. Typically, if the water heater is warm to the touch, you can benefit from a blanket.

  7. Reeves says:

    Should both of the thermostats be set to the same temperature or should the lower one be set to a lower temperature because of tank stratification?

  8. Fred says:

    Reeves, The thermostats should be set to the same temperature to avoid one element burning out before the other. Setting the thermostats the same avoids one element “overworking”

    • Arthur Sgambelluri says:

      The lower element works more than the top just because cold water refil enters at the bottom. Warmer water migrates to the top and requires less heat to raise temperature….stratification…

  9. Booster says:

    Would if I didn’t care about one element going out before the other? Would it save money to set one higher than the other? Which one?

  10. Kim says:

    I’m fairly sure you wouldn’t save energy, since the one element would have to work harder to make up the difference of the other one being set lower. The best way to save cost is to set them BOTH lower and to take shorter showers (getting done before the water runs cold!).

  11. ish says:

    we took a cold shower this morning at our new house, i was scratching my head wondering what the heck was wrong with the water heater! but thanks to this post my life just got brighter, thanks!!

  12. Rhett Frady says:

    Have a rental house. Young lady said water was not real hot and she ran out quickly. Lives by herself so not a lot of water used from the 50 gal tank. I suspected one of the elements and opted to replace both as the heater is just over 4 years oll.. Replaced both, water is much hotter, however, she still runs out. I put two of the 2 pronged elements in. Originally, it had a single and a double installed. Did not mess with temperature settings, which are at 126. Any ideas

    • Ted says:

      I have a tankless heater on my oil fueled boiler. The water is not that hot, and does not stay hot for that long. What temps should I keep them on. The low is on 140, and the high 180

  13. alex says:

    great post, it helped a lot, thanks!

  14. Ingrid says:

    This has been a GREAT help. We’ve wanted to do this for months and just have’nt known how.

    Question: Is there only one thermostat on a 32 gallon water heater? I removed both cover plates and the top one had only wires behind it.

  15. Kim says:

    Hi Ingrid,
    Yes, it’s entirely possible that your 32-gal only needs one thermostat. Ours is a 50-gal., so it has two. You can check your instruction manual (or search online; most manufacturers have .pdf’s you can download for all their models) just to verify if you’ want to be absolutely sure.

    But I didn’t have to go digging around for ours; they were right there behind each door, so I’m betting yours only needs one.


  16. YBR says:

    Thanks! Not only is this a good guide….that’s my new water heater in the picture!

  17. Frank Jones says:

    How do you know that both thermostats on an electric water heater are set to the same temperature? The numbers on the dial have no relationship to the actual temperature at which they operate(example: my new heater came set at 125 degrees, but the water at the closest faucet–about 6 feet away–was in the 90 degree range.)
    I raised the temperature settings an equal amount on both thermostats until I got 130 degrees at the faucet. BUT, I notice that in the shower, the temperature starts off at about 130, but then drops noticably after a few minutes; it doesn’t get cold, just a few degrees cooler. It doesn’t run out of hot water during any reasonable shower
    I suspect that there is a small “pool” of warmer water at the top that is used up first, then the cooler layer starts through.
    So, is my upper setting actually higher than my lower setting? How can I tell if the two elements are actually coming on, and turning off, at the same time?


    • Art says:

      Great diagnosis…you’re likely correct. Some upper tstats are known as double throw which do not allow both to be on at the same time, AO Smith. When you raise the temperature of the upper thermostat the lower thermostat will deenergize regardless of the lower set point.

  18. John Wilson says:

    We just had a new water heater installed after the old one burst. I asked the plumber if I needed a thermal blanket, he said no, the newer units had plenty of insulation and that wrapping them trapped more moisture around the unit causing it to rust prematurely.

  19. Paul&Aundrea says:

    I’m going to look into a thermal blanket. We live in my grandmother’s old house, and who knows how old the water heater is. It is just my husband and I and if we both shower back to back the 2nd one always runs out of hot water. This usually isn’t a problem since I like to shower at night and he showers in the morning. I didn’t even think to look at what temp. it is set at.

  20. James F Trogman says:

    Well and good. But what if the system does not have panels or a thermostat with ready access?

  21. Harry D says:

    I have a 75 Gallon Marathon (Rheem) water heater and I set the top thermostat at MED and Med is 125 degrees and the bottom is set at low or 120 degrees. I believe this is what the factory setting were (120 degrees). I assume that the temperatures is what you want to be the same. The 2 thermostats are not the same on this unit. The bottom has a medium setting temperature of 150 degrees and the top medium equals 125 degrees .. high setting for the top is 155 degrees and bottom is 180 degrees. Low setting temperature top 95 degrees bottom 120 degrees. This water heater is considered commercial although it is newly installed in a single family home. The plumber said the top and the bottom should be set the same (Medium) but that caused the water to register at 150+ degrees. I really don’t know what the factory setting on the thermostats were? I called Rheem and waited hours on hold but no one could tell me how they were originally set. I want the temp to be 120 degrees and I would like to have this water heater work as efficiently as possible and not waste energy. So 75 Gal Marathon how do you set the two different (range) thermostats. HELP!

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