Yet Another Water Heater Question

Mods. I’m going to start this here but feel free to move it somewhere else if you think there really isn’t a factual answer. I think there should be one, but what do I know.

My wife and I have been having a running battle since we moved into our newish house over a year ago. The house was 5 years old when we bought it and had a presumably 5 year old, 142 gallon natural gas water heater. (I should probably mention that I live in the San Francisco Bay Area just in case that makes a difference).

Anyway, with the price of gas and electricity continuing to climb I try not to waste it, but my wife is perpetually cold, and likes her really hot showers in the morning. I should add that I like a nice hot shower too… but I’m personally not into scalding. The water heater has a red dial on the front that lets you set the temperature of the thing. You can set it to either Low, A, B, C or Very Hot. I like it set to C, and she likes it set to Very Hot. So every time I go through the garage, which is usually 3-5 times a day, I change it from Very Hot down to C. And everytime she goes through the garage, she changes it from C to Very Hot. This has been going on for at least 8 months.

Sometimes she will not change it for a few days in hopes that I will forget to check, and then all of a sudden I will notice the water is hotter and it will have been reset to Very Hot. A few weeks ago I told her this was getting a little silly. She asked me why I kept turning it down from Very Hot to C and I told her I was trying to save money. She laughed and said that by turning it up she was saving money.

The Two Positions:

  1. Husband sets the temp down to C because MOST of the time we aren’t home so MOST of the time the water heater is just sitting there… trying to maintain the right temperature. Let’s say that at C it tries to maintain 120 degrees F and at Very Hot it tries to maintain 140 degrees F (I have no idea what the temperature really is inside the thing since I don’t have thermometer that can measure it). So if it’s set to Very Hot then all day long it’s using up energy to maintain the temperature difference between 120 and 140 degrees. (Yes I know it is insulated but when I’m at home by myself and I’m putzing around in the garage working on something for hours I hear it cycle on and off every 15 or 20 minutes. Presumably trying to keep the water at the right temp. In my mind, cranking up the temp means that the overall amount of energy used must be more “all things being equal”. For example, the time it takes me or my wife to take a shower doesn’t change depending on how the thing it set.

  2. Wife believes that by raising the temperature that means that when you take a shower you use less hot water to mix with the cold water so you don’t have to replace as much water and reheat that replaced water up to temperature when you are done using it.

So which is it Dopers? Which temp setting, C or Very Hot is the most fuel efficient give a typical house with 2 people living in it and both people working all day long? Just for the record we don’t have any TOU (time of use) charges here so the cost of a therm of natural gas is the same no matter what day or what time you use it.

That’s probably a 42 gallon. Not 142.

Anyway, does your wife shower with ONLY hot water? And it’s not hot enough on ‘C’? If that’s the case, there is likely something wrong with the hot water heater.

Or, some showers faucets have additional controls available that allow you to ‘pre-set’ the shower temp. These will just be additional knobs in the shower. In other words. Ya just turn it on with no need to set the temp. So, in that case, the water temp of the water heater will change the resulting water temp in the shower.

It seems a bit odd. We have our hot water heater set to about ¾ and there is no way a person could stand under the shower at full hot. Seems silly, but are you sure your Wife knows how to use the shower controls?

Had something happen with my Wife a few weeks ago. She said that one side of the shower head came out cold, and the other hot. :confused: Ummmm. I tried to explain that that is pretty much imposible with the way the plumbing works. And that I had never experienced this. She’s a smart girl, really she is. But that just threw me.

First unless you are actually hurting for money this is a very silly thing to argue about. Second if someone messed with my shower temperature they would be one seriously hurting dude.

The best setting for the water heater is the one that for the person who likes the hottest shower has the shower they want without using any cold water. Now practically speaking this means setting it slightly higher then that due to the burner on-off cycle, so that at the lowest temperature is still hot enough.

142 gallons is very large, perhaps you should look into a 50 gal water heater, just run the numbers and see if it makes sense to throw that thing out and start over.

As for your question I think C uses less fuel, but A would be even less, what’s your point, C is not hot enough. It’s not a issue of money savings, it’s one of comfort. If you want money savings perhaps consider a super low flow shower head, typically showerheads are about 3g/m, super low flow ones are about 1g/m - cutting your hot water energy use (and water use) but almost 1/3rd in the shower and they work much better then the old low flow ones. One final word is the best energy savings it to shut that down and you both get cold showers.

I had this happen to me, what it was a uneven mixing of hot and cold water, so the shower head is not going side to side hot/cold, but hot and cold pulses. This was caused but other demands on the house water supply at the time of the shower. Now the cold pulses are very short and if you moved your hand across the stream you could feel it’s cold on one side, hot on the other, but it’s a time difference, not a right/ left thing.

In your area, it might not get down to freezing in the garage, but unless the garage is heated, you might be spending money to keep the tank warm for hours. Have you considered “instant” or tankless heaters? These store little or no hot water, but heat it up very quickly the minute the demand is sensed from the water flow. They work best if installed near the faucet, and some are small enough to be mounted under a bathroom sink. The nicest part about them is you aren’t paying anything to heat water when you aren’t using it, and you aren’t paying to store and replace the heat lost over time.

That, plus a more sophisticated shower head – they even make thermostatically controlled ones with multiple presets, I believe – should make shower time for both of you much more fun.

Since you’ve already spent 8 months in a tug-of-war with the water heater, why not spend another two and do some experimenting.

Set it to medium and tell her to open the hot full and not mix in any cold when she showers. You might still have to mix in a little cold.

Then set it to high and you’ll have to mix in a lot of cold and she’ll have to mix in a little.

Then check the bill at the end of the month. Or I suppose you could just do it for a week but hen you’d have to pay close attention to the gas meter.

My feeling is that the highest setting is most expensive because the temperature difference between the inside & outside of the tank will be greater, therefore a higher rate of heat lost through the walls of the tank.

I installed one of these (Stiebel Eltron electric) and I think it’s great. You only pay for what you use; no standby losses. Winters in DC can get down into the 20’s sometimes so you have to be aware of that and set the shower controls accordingly. In the coldest of winters I mix in no cold and have to reduce the hot flow rate slightly but I can still get water that’s hotter than I can tolerate.

? So the shower head was cold on one side and hot on the other? But not a right left thing?

Not sure what my Wife experienced. But I think it had more to do with trying to get in the shower before the hot water had really come up. If you put your hand in the mist of the shower head, It feels much colder than the main stream due to evaporation. Once the shower and air in it warms up a bit, you can’t tell the difference.

  1. It cannot be a 142 gallon heater. They don’t put water heaters that big into houses.

  2. 120f is sufficiently hot for any human being’s shower. That is HOT. 140f hot water will severely burn skin in about ten seconds; nobody could possibly shower with water that hot. If your wife is showering with pure hot water and it’s not hot enough, you may be losing heat somewhere or the heater’s thermostat is on the fritz.

Check for places where the pipes may be losing excessive amounts of heat. Consider buying pipe insulation. It would help to compare hot water temps at different taps; if you have a basement sink near the heater, compare its hot water to what you’re getting in the bathroom. If there’s a big difference, you need insulation.

Check the temp of the water near the source. If “C” is the setting just below Very Hot, it should be at LEAST 120. If it’s not, your water heater may not be heating the water enough. ( Also, water stored below 120 is at risk of breeding bacteria.)

The ideal solution - and it’s now code in many places - is heating and storage of hot water above 120, but using a mixing valve to reduce the possibility of scalding injuries.

As for tankless heaters, I strongly suggest you study them very carefully before buying; they’re all the rage and fad now but I’ve heard a lot of people end up very disappointed with them, especially if they buy smaller models.

No it was not cold on one side, hot on the other, but could have appeared so under certain circumstanses. An anology: You go out your front door in January, your rear door in August, You conclude that the temp is different on the different sides of your house.

Unless the temperature of the hot water, when on “very hot” is still cool enough to stand in the stream in the shower (In which case you have other problems) you are wasting energy by using the “very hot” setting.

Showers are not the only thing that uses hot water. Laundry, Diswasher, hand washing, and all the usual things also use hot water. Laundry doesn’t need water to be all that hot. (And if you think it is providing antiseptic effects from heat, you just don’t understand) The Dishwasher heats it’s own water, although it can use a boost. Handwashing, feh.

So, the amount of energy is a total. How much energy will be used to actually provide appropriate temperatures for various tasks. People decided how hot a shower should be, and can adjust dynamically to taste. Mechanical use is pretty much take what you get.

The tank, and every inch of hot water pipe in the house radiate heat. The heat radiated in the garage is pretty much wasted. Heat radiated in the house is a wash in the winter, and a double whammy cost in the summer, since your airconditioner will automatically increase cooling to make up for it. Higher heat, higher radiative loss. (All this is mitigated very much by pipe insulation.) Cold water running out of the spigot when you first turn on the hot water is wasted heat energy, already lost from the last time the pipe was filled with hot water. (Hotter water wastes more, insulation saves more.)

The amount of cold water mixed in doesn’t change the thermodynamics of how much it costs to heat the water. How much cold water is added to the tank doesn’t either. The temperature difference is what matters, and the amount of water used, if greater, only matters in energy terms if the intake water is very cold, or the output temperature is very hot.

But. Don’t win a fight that costs you nothing to loose. The difference in cost is pretty small, for the difference in your dear wife’s feeling of being put upon. Let her win. Be gracious. The warm feeling she has won’t just be limited to the water.


If you’re going to have this ongoing discussion with your wife, it would help to define your terms. Use a digital thermometer to see how hot C and Very Hot really are. The hottest bath water you’d dare to get into is probably between 104° and 110°. The coolest safe dishwashing temp is higher than that, (I don’t remember the number.)

As you know, the most energy use happens between the times when you’re actually using hot water. The tank cools, then clicks on to heat it up again. You can save money on that by putting an insulation jacket on the tank. You can buy one precut from Home Depot, or, if you know how to operate scissors and duct tape, you can make a thicker one yourself from a roll of insulation. A whole roll will be cheaper than the precut jacket.

By the way, all this fiddling with the control on the heater is probably wasting gas, too. :smiley:

Of course – if you buy the wrong size, you will be disappointed, just like if you get a tank-type one too small. Calculate the temperature rise you want for the flow you need, and size the unit accordingly. Or get professional help.

I have a tankless water heater (natural gas). It is a small one but supports showers, kitchen and laundry. Monthly gas price is cheap too, less than $15 here in Bogotá, Colombia. But, I think gas is cheaper here than in the US. If you get one, get one that will support your usage.

That is possibly the worst anology I have ever read. Did you read the OP?

And you did contradict yourself a couple of times in your post.

kanicbird Have you ever done any plumbing?



what is your point?

The lower temperature is going to be more efficient. Even though you heat up less water in her scenario, that water is heated to a higher temperature, so there shouldn’t be any energy savings that way. The temperature difference issue you mentioned will increase the cost of maintaining the water at the higher temperature.

Now, there are other issues beyond cost efficiency. My wife enjoys baths, if the temperature is set too low, she runs out of hot water. A higher temperature means you can have more “bath hot” water than a tank set at the exact temperature needed.

If she’s got an issue beyond cost efficiency, then you may want to pay the extra money for her comfort. If it’s entirely an efficiency issue, she’s mistaken.

It’s not a “hot” water heater. It heats water from your municipal supply or your well which typically arrives at around 55° F, which isn’t hot.

Who does someone always have to jump up as say this, which is not even true:


It’s a term we use for such a device, by using it you communicate what you mean clearly.

Sorry to offend you, but it’s a redundant, illogical expression, and we’re allegedly about fighting ignorance. YMMV

It’s not a expression at all it’s a noun which is defined as such in the dictionary. Now I don’t know the etymology of the word, I would WAG it is a shortened form of hot water tank and water heater, but it is what it is.

Now you have to excuse me while I go to the nearest ATM machine and use my PIN number and get some cash to buy some SCUBA self contained under water breathing apparatus :stuck_out_tongue: