How hot is your water?

Thanks to a comment the author posted on a blog I wrote, I had the fortune to discover the great energy savings blog Energy Boomer.  While perusing the site I discovered this article on using a meat thermometer to save money on hot water.  This simple yet ingenious idea is a great way to determine if the water in your hot water heater is set at too high of a setting.  If your hot water heater is set too high you are wasting energy AND money!

Birney, the author of Energy Boomer, recommends a target temperature of 130 °F.  On his post he says, "Any temperature less than 120 is too low for health reasons (mostly referring to Legionnaires disease). Any temperature above 140 is wastefully high if you want to save money on your energy bills."  He recommends a temperature of 130 ° F.

I last lamented about how hard it was to set my water heater to the appropriate temperature back in April of 2009.   In my blog for better water heating temperature control I had a very important disclaimer:

Recently, I decided that in order to save money on my natural gas bill, I would turn down the temperature on my natural gas fired water heater. (Caution: If you do this without telling your wife, she may get upset when she asks you why she ran out of hot water during her shower and you inform her it’s because you “made a few changes”.)

I decided to take Birney's tip and see how hot our water is.  Sure, I wasted some water, but the ends justify the means.

I used our digital meat thermometer for this test.  After finding some batteries in our battery drawer I popped them in the meat thermometer and started the hot water.   A few minutes later the temperature stabilized and I was happy with what I saw.

My hot water is at a comfortable, yet energy saving, 123.6 ° F.  It is important when doing a test like this to make sure you haven't done laundry, taken a shower, or washed dishes right before testing the temperature or else your hot water heater may still be in the process of heating up the water.  Of course that is not the case if you have a demand (tankless) water heater.

So readers: What's your water heater temperature set at?

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My ideal hot water system would be to have some solar collectors on the roof to pre-heat water in a large tank in the basement. Then a "tankless" heater would bring that water up to household temperatures. Probably in the summer that would do nothing as the solar would provide sufficient energy. But in the winter (especially in weeks like this one where I'm looking at several consecutive days with no sun at all) I'd still have hot water.
Seven years ago we installed an electric tankless water heater by SETS (Now Hubbell). We appreciated how little space it takes up in our small home, but I would not likely do it again. We have to run, and waste, the water for more than a minute for the temperature to stabilize, and even then it often cycles between cold and very hot, particularly if we change the flow of water. We haven't found anyone with real expertise with these units to help us refine the settings. The Manufacture hasn't responded to our contacts. Does anyone have a better experience with more recent technology? I wonder if a better configuration is to have a small tank water heater for immediate hot water and a tankless water heater on the same line to provide continuous hot water flow?
My cousin has a similar problem with his gas tankless heater. He problem is caused by low flow fixtures. His heater requires at least 1 gpm of flow before it will provide hot water. He had to remove the restrictors from most of his fixtures. Hope this helps.
Also keep in mind that depending on your house's plumbing layout, the stabilized temperature at the tap may be a couple degrees colder than in the water heater. I know my hot water is routed through the attic, and while there is fiberglass insulation and the pipe of somewhat 'wrapped' it'll drop 2-3 degrees before it reaches the tap.
One little flaw in the 130 degree temperature argument... If you reside in a house with many people, or people who use hot water for long durations, 130 degrees may not be enough. Setting the temp higher than 130 degrees allows for more and/or longer showers, for example. If you've got five people who all take showers in the morning, a setting of 130 degrees probably won't work well. Sure, there's the argument of having a larger tank, but then do the savings really pan out? And what if you can't reasonably change out your tank for a larger size?
The solar+tankless idea sounds attractive, but I've run an analysis on this approach and (financially at least) it's not such a great plan. Both a solar and a tankless hot water heater will save about 2/3 of your water-heating energy costs. But if you install both (at 2x the cost), they are each competing for the same two-thirds savings and there's "not enough savings to go around". Stated differently, it saves a lot of energy but the payback is stupidly long. Also, I'm told not all tankless units can cope with the high inlet temp solar provides: you have to make sure you get a modulating unit that's rated for the high temp...

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