Our hot water heater is in the basement and it's electric. We were having a problem with the second person taking a shower not having enough hot water. The first thing we did was look for insulation for the hot water heater. We live in a small town, so no one had a hot water heater blanket for us to buy. I then started looking around on the internet for options, and one that I ran across was a radiant barrier for the hot water heater. While I can't really understand the concept, I decided to try it anyway. I went to the local Dollar tree and bought five of the reflective windshield barriers for cars ($5 plus tax). I came home and wrapped them and taped them around the hot water heater sides and top and connected it with duct tape. I followed online directions that the reflective surface needs to be next to air space, and so put it facing out-words, even though my brain was saying, "shouldn't you be reflecting the heat back to the tank?" Amazingly, it works. Why? It still seems hoky. I can't tell if it helped with the cost of electricity, as this was heading into winter and we have electric heat. We also looked for and found a few lengths of hot water pipe that needed insulation and fixed that.
The other thing I did was bought some low flow shower heads and some new aerators for our sinks to conserve on hot water. Now, even when I am the third person in the shower, I find myself adjusting the water temperature down (and I LOVE a hot shower.)
Soon, we will be assembling the parts in the basement for our solar water heater. . .
In order to understand how the blanket works, it might help to stop thinking about it at reflecting heat and start thinking about it as reducing the amount of heat your water heater emits to the surrounding area. If you are interested in learning more about radiant heat transfer check out this website :
Adding insulation to your water tank will reduce heat loss from your water tank, but only marginally help that third person get a hot shower. Let me explain : when the first person starts taking a shower, the water tank starts out hot - usually somewhere between 120—140 degrees Fahrenheit. As the first person showers, hot water is removed from the tank and replaced with cold water. Soon the heating element in the tank will turn on to try to keep the tank at the heating setpoint. The heating element in a domestic water heater usually isn't large enough to keep up with the full flow of the shower. Usually enough hot water for a shower is provided because there is enough extra heat in the tank to make up the difference. So, after the first person showers, maybe the tank temperature has dropped 15 degrees. If nobody else gets in the shower, the heating element stays on for a little while and gets the tank back up to temperature. However, if someone else gets in the shower before the tank heats back up,the heating element can't keep up with heating the flow of incoming cold water.
When you installed the low flow shower head, you reduced the flow of cold water into the water heater. This means less load on the heating element. Maybe even low enough that the heating element can keep up completely. So now, at the end of the first shower the water temperature in the tank has only dropped 5 degrees, or maybe not at all.
Most water heaters have a thermostat somewhere on the tank. If you are curious, check out what the tank temperature is immediately before and after you shower. You could even put your old shower head back on and check the temperatures before and after.
Lastly, remember how I said that water heaters are usually kept somewhere between 120 and 140 degrees Fahrenheit? Well... and here is where the real energy savings are. If, with your low-flow fixtures, you now find that you are having a comfortable third shower, you could lower the setpoint temperature of your tank. This will reduce heat loss to the surrounding area ALL THE TIME. I suggest lowering the tank temperature 5 degrees at a time until you find the point at which the water gets too cold.
I hope this helps and that my descriptions are clear! Feel free to ask questions.
Thanks for such a great and thorough answer. Of course, I have looked at a radiant barrier explanation before, but the it doesn't describe how it stops the heat loss, just that it does. I think I should have been from Missouri. . . My water heater is set on 120, and as I use a dishwasher, it may not work to turn it down further. However, soon I will have a second water tank being filled by hot water heated by the sun to draw from. I am hoping at that point to be able to turn off the electric tank and just use it as a holding tank, or if that doesn't work, cutting it out altogether. We are trying to move toward going off-grid.
You are welcome. One option with solar hot water is to put a small instantaneous water heater on the outlet of your solar-heated tank. It will come on to heat your water the rest of the way up to setpoint and will only come on if the water isn't hot enough already. Because it is not a large tank you won't have continuous ambient loses to the surrounding space. If you are crafty you might be able to modify your existing tank/heater to work in a similar fashion.