Hot Water Heater Timers

The energy saved would be equivalent to the amount of heat lost through convection and that only applies to the time the water heater is shut off. My guess is that you would be better off installing a water heater blanket to increase the insulation value. A blanket would help you save 100% of the time, not just when the heater is off. If you already have a blanket, I doubt that you will notice a difference.

 

I've got news for you all. I use one in my house. I noted some electric bills for 3 months before installing the timer and the same 3 months after installing it. Result: The timer lowers my electric bill by an easy $30/mo. I've set the timer to come on at 5AM and off at 9AM, then on again at 6PM and off at 10PM. This is plenty of time to have an abundance of hot water for a shower in the morning, and for cooking and cleaning in the evening. If a laundry day comes, my wife knows to hit the override button which puts the heater on full time until the next off cycle arrives.

 

I doubt it will save much because you are only saving on some heat losses at the tank. If it saved 5% I would be surprised. There was a timer on the water heater in one house we were in, but I never used it.

The best way to cut tank losses in an existing tank is to insulate the piping to and from the water heater, and to insulate the water heater itself with an R6.7 or R11 blanket. Typically the tank's own insulation is around R8. With an electric you can insulate the top as well (you can't do this with gas since it is to close to the flue.)

There are also some changes that can be made to the piping adding external traps to prevent a thermosiphon (rising hot water in the pipe being cooled and falling back into the tank.) Newer tanks may have some sort of internal traps to reduce this tendency.

Use the model # on the heater to pull up its energy guide. From that you can determine its estimated annual energy demand. You should also see its efficiency rating on the nameplate or the guide. For an electric almost all the efficiency loss will be tank/piping heat loss. That's the portion you can do something about with insulation, timers, traps, tankless systems, etc. (other than cutting actual use.) With a gas water heater you lose an extra ~15% up the flue unless it is a condensing unit (rare.)

 

For me that would be 300 kWh. That's more than I use in hot water in a month. Doesn't compute unless your electricity is around $0.50-1.00/kWh. The tank losses should not be that high.

 

Well, if nothing else could you downsize to a 40 gal? That coupled with a blanket, low-flow showerhead, and time should put a dent in your energy use. Since you're all electric, you might seriously look at solar thermal. I think if you're on electric heat you'll get a pretty good bang for the buck (much better than gas water heating for a couple of reasons). There's a 30% fed tax credit for solar thermal installs so that could make it attractive to you. The idea situation would be solar thermal with tankless backup. I'm surprised that the electric tankless models don't have a significant savings over a traditional.

 

I use a timer. I also shut off the heater before I take my shower. When I'm done, the water in the tank sits at a lower temp, and thus cools slower. I then heat it up before my next shower. One bit of advice: Have everybody take showers back-to-back so the water in the pipes doesn't cool down between. Be sure the tank is up to temp before the first shower, and turn the heat off just before the last shower. All this combined will definitely save energy.

One thing to note... especially with a 50 gallon tank - having it off doesn't mean that you'll have "cold water" for washing your face, etc. It just might not be blistering hot. 50 gallons of hot water can (should!) certainly take you through a normal day without the heater on.

Interestingly enough, I don't have an electric heater, though mine has an electric switch that controls the exhaust fan, and thus the electronic gas start. I can just use a regular lamp timer. And I have a remote on it so I can switch it from upstairs at the shower. I have a pilotless gas heater.

Running the heater once a day will definitely save energy as opposed to having it tick on several times just to maintain. Now much it saves is debatable - but it WILL save.

 

When both my parents were still alive, they lived the last 10 years of their life in a seniors community, typical side-by-side condos with nat gas heat and electric hot water.

They got in the habit of using the breaker to turn off the hot water tank when not in use. Even with power as cheap as it is in Manitoba, this saved them $20 a month.

The circuit breaker went haywire after 9 years of this. So I picked up a brand new $20 two pole 20 amp breaker, took me all of 5 mins to put it in.

With the nat gas hot water tank, I don't bother turning it off unless I'll be away for awhile and nobody else will be in the house. It's a bit of a PITA to relight the pilot, but I finally got a bbq lighter to take care of that issue.

The only gas I use in summer is for the hot water tank, and my gas bill is usually $40-$50 a month. Here at least, electric heaters are cheaper to run. I like the gas tank as it recovers much quicker, never run out of hot water

 

Look, you are trying to reduce the same heat loss whether you use a time or insulate the tank. What does using a timer accomplish? It reduces losses by allowing the water in the tank to cool (but you have to heat it back up so some of the savings is lost again.) The average temperature of the tank during the day is less as a result of the timer so losses are less, the question is how much? Now what does insulation do? The same thing, it reduces the average wall temp...but continuously.

Your tank is likely to be about R8 and have about 1" of foam insulation. No, the water heater wall will not feel hot with only 120 F on the inside. 120 - 70 = 50 F differential. Wall temp will be about 70 + 50 / 8 ~ 76 degrees. Insulate it and it will drop to about 73 degrees...but you will cut the heat loss almost in half.

Those short runs of pipe near the water heater should be insulated if possible. Copper is a great conductor so that nice insulation already on the tank is being compromised by the pipe. (There are restrictions on this with gas because of flammability issues.)

For my tank the blanket payback is about 2 years. (I did a semi-rigorous heat transfer calc accounting for the areas I can't insulate as well.)

I'll take a look at the timer claims, but it seems more logical to spend $25 on the blanket first rather than $40 or more on the timer. "Both" might be the answer you are looking for.

Current electric water heater energy factors are about 90%. So the max theoretical reduction is about 10% if you were to waste zero heat in storage. Using a timer won't knock it to zero, because the tank will cool while the timer is off and have to be reheated. (darrelldd will come close to that because he is not allowing the water to heat again while in use, so he is using like a modified demand system.)

 

My electric water heater is less than 2 years old so I haven't bothered with a blanket.

Should I?

 

I can't believe you don't wash your hands or your dishes with hot water! That is what kills the germs or the bacteria. Don't be offended when I don't shake your hand or eat at your home anytime soon. I'll just wave from afar and eat take out.

 

Demand water heaters!

If you have electric, blanket the hell out of it, set a timer to turn on a couple of hours before your major use,, (assuming you don't have time of day metering!) There is no reason after your evening shower, to reheat the water to ~120f have it cool overnight and the next day, cycling on and off doesn't have to happen. A water heater will recover quite quickly. The water in the tank will remain hot enough during the day to wash hands, laundry and dishes.

Every little bit helps,

Icarus