Not saving money by lower temp setting

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RonL1

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We had our heater set for 140 lower and upper elements... we thought let's save a few nickles and lower the temp down. So, we lowered the elements to 125 and now the tank runs much longer to reheat. It seems we must be using more water at the 125 degree mark so it's taking longer to get it back up.
 

Reach4

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The standby heat loss will be less at 125. But if you are running out of hot water now, then crank it up some.
 

WorthFlorida

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You're using the same amount of water, just more of it now flows through the water heater. When you run the hot water you set the faucet to a position for the a water temperature wanted. At 140º you'll mix more cold water than hot water to get it down to say 105º. At 125º you mix less cold water with more heated water to get it to 105º all assuming the faucet is drawing the same amount of water per minute. Energy wise you're using the same for either setting. The only difference is what Reach stated, at 140º you will lose more heat in standby mode, that is heat dissipated into the air through the insulation and piping while not in use. If the water heater is manufactured since 2010, EPA standards for WH went up and electric WH loose very little heat through the jacket insulation as from years past.
 

RonL1

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You're using the same amount of water, just more of it now flows through the water heater. When you run the hot water you set the faucet to a position for the a water temperature wanted. At 140º you'll mix more cold water than hot water to get it down to say 105º. At 125º you mix less cold water with more heated water to get it to 105º all assuming the faucet is drawing the same amount of water per minute. Energy wise you're using the same for either setting. The only difference is what Reach stated, at 140º you will lose more heat in standby mode, that is heat dissipated into the air through the insulation and piping while not in use. If the water heater is manufactured since 2010, EPA standards for WH went up and electric WH loose very little heat through the jacket insulation as from years past.
I was thinking even though I would use more of the 125 degree water, it would take less energy to heat it back.. but that does not seem to be the case. My wh, is old... it's a maytag model, discontinued, can't get parts of any kind for it, but it still runs fine. And when you feel the outside of the tank, it's ice cold... it must be well insulated. I was going to buy a blanket for it, but being cold like that, I didn't see the need. I'll have to play with the sttings and see how it reacts. I can monitor it using emporia energy monitor. Measures by the second,minute, hour, day,month or year. Wats, amps... it's a nice tool
 

jadnashua

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You're using the same amount of energy because at 140, you aren't using as much to get the shower temp safe.

As said, you're putting the same amount to energy into the tank to get your shower water whether it's 140 or 125...think of the WH as a battery that has different amounts of storage. At 140-degrees, it's storing more energy than at 125, but what you end up using is the same.
 

Reach4

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Your next electric water heater may be a heat pump model.

There the numbers change. There is not only the standby losses, but it gets harder to pump heat into a hotter water. I understand that this does not apply now, but when you spring a leak, a heat pump WH may turn out to be the economical option despite the higher initial price.

For you current WH, if 120 degrees leaves you wanting for shower time, you could try 130, rather than only going back up to 140.
 

jadnashua

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Where I live, you're required to have a tempering valve, which otherwise would be required if the supply exceeded 120-degrees, so if you don't have one now, you should probably consider it. A tempering valve just means you're mixing some cold in before it gets to your shower if the outlet exceeds its setting.

140-degrees over time, can help prevent nasties from growing in the warm water. It won't kill everything, but does slow them down more if it doesn't kill than versus running it at 120, so that's a consideration. It does make the tank function as a larger one. Again, think of the WH as a battery...hotter water means more stored energy, but it costs the same as you use it. Because the temperature is higher, it does mean there's more heat that will escape. Electric WH are more efficient than gas ones because they have insulation all around them versus a gas one where there's a flue up the middle that can't be insulated or it wouldn't work!
 

Bilmocraig

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There is not much difference in changing the temperature. You're using the same amount of water. Just more of it now flows through the water heater. When you run the hot water, you set the faucet to a position for the water temperature wanted. At 140º, you'll mix more cold water than hot water to get it down to 105º - assuming the faucet is drawing the same amount of water per minute. Energy-wise you're using the same for either setting. The inspired budget printables made me think about all of these when planning and adjusting my finances.
 
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Fitter30

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Screenshot_2022-06-26-07-29-56.png
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1.1 gpm difference in hot water @ 6 gpm. 3 gpm flow rate .5 difference in hot.
3 gpm 100% hot water = 1749.3 btu's @ 70° rise
2000 watt element = 6600 btu's
 
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Master Plumber Mark

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This post is from way back in March...

All you have to do is go buy a 25 dollar water heater jacket and wrap the heater with the jacket
and it will save you about 25% on your eclectic bill ......
I have noticed a difference in the performance
of a heater before and after the jacket was installed where I lived
it was set on a lower temp but it felt much warmer due to the jacket

try this simple fix next
 

RonL1

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This post is from way back in March...

All you have to do is go buy a 25 dollar water heater jacket and wrap the heater with the jacket
and it will save you about 25% on your eclectic bill ......
I have noticed a difference in the performance
of a heater before and after the jacket was installed where I lived
it was set on a lower temp but it felt much warmer due to the jacket

try this simple fix next
Not sure if this would help much, my heater is ice cold to the touch.. to me that says it's keeping all the heat inside. A blanket could help a bit. I may give it a try anyway. But keeping an eye on my usage, my kw seems to have been reduced by almost 100 kw a month.. I will keep watching it. This may have just been a coincidence.
 

wwhitney

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Say you install a new electric resistance water heater, and the UEF is 0.92 (a value arbitrarily picked from one water heater I looked at). UEF is apparently based on a 125F storage temperature, with some draw profile(s) I don't know the details of, and 0.92 means if you put in 100 kWh of electrical energy, you get 92 kWh into delivered hot water.

So worst case, 8 kWh is standby heat loss at the tank (I'm not familiar with the standard, so some of that 8 kWh may be losses that don't vary with tank temperature). Say ambient temperature at the water heater is 70F. Then that's 8 kWh at a 55F temperature delta. If you are running your water heater at 140F, the temperature delta is now 70F. That would make the standby heat losses 70/55 * 8 = 10 kWh, worst case.

That means best case, if you turn your modern UEF 0.92 tank electric water heater down from 140F to 125F, and your usage pattern is at all close to the draw profiles used in the UEF rating standard, you'll be reducing the energy usage from 102% to 100%. I.e. you'll reduce your water heater energy usage by around 2%, best case.

Now if you have an older water heater with a lower UEF (if it were measured), the savings would be greater.

Cheers, Wayne
 

jadnashua

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With a higher storage temperature, you'll essentially be able to take a longer shower which might entice you to do it. If that's the case, it will cost you more to heat it because you'll be using more hot water. But, for the same length shower at the same outlet temperature, the same amount of energy will go into the tank.
 
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