Mustache that electric water heating bill!

[Alex in Virginia]

Through trial and just a little bit of error, I've found that I can have hot water just about any time I need it without having to run the hot water heater continuously.

I've got a timer hooked up to the water heater, but you could also do this the low-tech way by just turning the hot water heater on and off at the electric service panel.  I have found that 1.5 hours of water heating will keep hot water hot for at least 8 hours.  The only activities that will run me out of hot water sooner are doing laundry or running the dishwasher (which I of course do during the 1.5 hours that the hot water heater is on, although most of the time I do the dishes by hand).

So, in my case, the hot water heater goes on between 6am and 7:30 am, turns off, and then comes back on from 4pm to 5pm.  (That 1 afternoon hour works for me because I'm in bed by 11pm usually.)  This gives me hot water all day and night*.

That's a total of just 2.5 hours of water heating time a day -- a big mustaching from keeping that electricity guzzler on 24/7!

Try it... you'll like it. :)

Alex in Virginia

* OH! And did I mention that this is BEFORE wrapping a water heater thermal blanket around that sucker?!  That's my next move (and the blanket is just $20 at Home Depot).

[Freda]

Love this!  My house has two hot water heaters.  Hubby and I both shower at night. We could cut down on a lot of waste. Thanks for sharing!

[Arbor33]

I've been doing it the low tech way myself and only turning it on as needed.

When you set up the timer, what setting do you have the hot water tank on? (High, low, medium)

Have you tried different settings and seen what you can get away with?

[Alex in Virginia]

I've been doing it the low tech way myself and only turning it on as needed.

When you set up the timer, what setting do you have the hot water tank on? (High, low, medium)

Have you tried different settings and seen what you can get away with?

Hah!! I haven't the foggiest idea!  Thanks for asking -- I'll see if I can cut the cost even further. (The timer works for me because otherwise I'd have to WAKE UP (what!!!) at 5:30am every day to turn the hot water heater on.)

Alex in Virginia

[the fixer]

I'm a little confused why this would work... wouldn't leaving the heater off for several hours lower the temperature even a little, so more energy is required to reheat that water during the on cycles? It seems to me like you could only save energy this way by turning off the heater for longer periods of time and allowing the water inside to reach thermal equilibrium (totally cold) and keep it that way.

Can you hook up a Kill-A-Watt to see if this is actually saving electricity?

[Alex in Virginia]

I'm a little confused why this would work... wouldn't leaving the heater off for several hours lower the temperature even a little, so more energy is required to reheat that water during the on cycles? It seems to me like you could only save energy this way by turning off the heater for longer periods of time and allowing the water inside to reach thermal equilibrium (totally cold) and keep it that way.

Can you hook up a Kill-A-Watt to see if this is actually saving electricity?

My electric bill tells me this works.  The water heater operates by seeking to maintain AT ALL TIMES that it is turned on a designated "hot water" temperature.  For me, that means that the unit would be working to do this from 7am to 4pm (9 hours!) and from 5pm to 5am (12 more hours!) when it is not needed but would continue to compensate for the cooling of the water all that time.  I've reality-tested turning the water heater on from a fully cold start (NO heat at all in the water coming out of the tap) and it only takes 30 minutes for the water to become hot enough to bathe, run wash, etc.

The same train of thought you have brought up would lead one to keep the central air conditioning unit operating 24/7 to maintain a set temperature on the argument that the ac will have to run harder if it has been off for a while.  The same logic would tell you not to lower your thermostat at night in the winter because it will be that much harder to rewarm your place the next morning.  Well, the utility bills don't lie.  In my experience it is ALWAYS better (cheaper) to turn off these various energy-consuming units when their output is not needed.

I'm happy, anyway...

Alex in Virginia

[the fixer]

I was an astronomy major in college with lots of physics and thermodynamics. If you've got lower utility bills, that's all I need to believe it.

Thinking about this more, it may be due to a water heater being less efficient at maintaining higher water temperatures. This follows from Newton's Law of Cooling, that the rate of cooling of the water in the tank is proportional to the temperature difference inside and outside the tank. So it would take twice as much energy to maintain a 40 degree temperature difference than a 20 degree.

[AJ]

If it lowered your bill, great! But I'm not exactly sure how. Most electric water heaters only run about three hours a day anyway - less if they are newer. The vast majority of the electricity used by the heater is in heating up water to replace what you have used - standby losses are a much smaller percentage of the energy use.

I did this very same thing once and noticed zero difference in our bill. So, I guess YMMV.

http://michaelbluejay.com/electricity/waterheaters.html

[Freda]

Now I'm wondering if I should shut the water heater off when we go on vacation. :)

[Spork]

Now I'm wondering if I should shut the water heater off when we go on vacation. :)

I think that is a definite win.  For a while, we had a "weekend house" (which turned into our actual house at a later date).  If electric H2O heater was on: it was about $30 a month.  If we powered it off when we left, we got the "minimum charge" the electric company bills.

[Alex in Virginia]

Hah!!

I just finished washing my dishes with plenty of hot water... TWELVE HOURS after the electric water heater timer cut off this morning.  Guys, there seems to be no reason to keep that sucker on all day (unless you're going to be using it over and over throughout the day instead of during discrete time windows).

UPDATE! April 5th:  Had plenty of hot water to do my dishes SEVENTEEN HOURS after the electric water heater timer cut off this morning (uhh... that's yesterday morning now, actually!)

I'm just waiting to see what my next electric bill shows.

Cheers!

Alex in Virginia

[MooreBonds]

Hah!!

I just finished washing my dishes with plenty of hot water... TWELVE HOURS after the electric water heater timer cut off this morning.  Guys, there seems to be no reason to keep that sucker on all day (unless you're going to be using it over and over throughout the day instead of during discrete time windows).

I'm just waiting to see what my next electric bill shows.

Cheers!

Alex in Virginia

2 comments:

What is your water heater thermostat set at? Is it a temperature number (i.e. 120 degrees), or a relative setting? (hot, hotter, hottest) You can save money my keeping the thermostat set at a lower temp (like 120 degrees) and leaving it on all the time.

As another poster mentioned, there's more energy used to heat up incoming water - and heating the cooled-down water after it's been shut down - than it takes to maintain a full tank of water at 120 degrees, just like it takes less energy to maintain your car's speed vs constantly accelerating and braking.

Also, one comment about bacteria - while it's not as much of an issue for people with healthy immune systems, legionella bacteria can grow like crazy when the temperature is between about 95 degrees and 110-115 degrees. If the heater is set at 125+, it can kill them....but when you're constantly cycling the heater on and off, that water in your heater will be constantly cooling down, and spending most of the time in the 105-115 degree range. If it's spending most of the time at 110-115 (or less) because you keep turning the heater off, you could be growing quite the culture of bacteria in there

Legionella is a naturally occurring bacteria in most water - it's just dormant in cold water, so it's not a huge issue in small levels and for people with healthy immune systems...but I still wouldn't be going out of my way to keep a 'colder' water heater setting.

[Alex in Virginia]

What is your water heater thermostat set at? Is it a temperature number (i.e. 120 degrees), or a relative setting? (hot, hotter, hottest) You can save money my keeping the thermostat set at a lower temp (like 120 degrees) and leaving it on all the time.

As another poster mentioned, there's more energy used to heat up incoming water - and heating the cooled-down water after it's been shut down - than it takes to maintain a full tank of water at 120 degrees, just like it takes less energy to maintain your car's speed vs constantly accelerating and braking

Thanks for asking that.  I checked and the temperature was set at 150 degrees (WHO did that!?).  Anyhow, I turned it down to 120-125.  I also took the opportunity to install a thermal blanket around the water heater.  (BTW, there are red letter postings all over this water heater warning about scalding if the temperature is set above 125 degrees.)

As for the premise that the laws of thermodynamics are going to negate all or most of the benefit of limiting the time the hot water heater can actually turn itself on... well, all I can say is that there must be something else also working here because there's no question that my electric usage is reduced by the use of timers on electric systems such as air conditioners and hot water heaters.

Cheers...

Alex in Virginia

[Spork]

for what it's worth: I had a plumber recommend NOT using a thermal wrap on gas water heaters.   I forget the exact reasoning, but I suspect it had to do with messing with airflow to the fire.  He claimed (?) that the insulation on the heater was enough.   I can't say I have enough experience to agree or disagree with him... just passing that along.

[Alex in Virginia]

for what it's worth: I had a plumber recommend NOT using a thermal wrap on gas water heaters.   I forget the exact reasoning, but I suspect it had to do with messing with airflow to the fire.  He claimed (?) that the insulation on the heater was enough.   I can't say I have enough experience to agree or disagree with him... just passing that along.

Yes, there was some cautionary language on the packaging for the thermal wrap to that effect.  Remember, with a gas heater you have a live fire inside the water heater! :O  But my water heater is electric so there's no issue of covering vents, etc.  It's all good.  :)

Alex in Virginia