Electric water heater: OK to turn it off?

[thinkxingu]

Originally Posted by SailinAway

What on/off cycles? The water heater would be off all the time, unless I come to my senses in the fall and realize I don't enjoy cold showers. However, there are other ways to heat bathing water, e.g., wood stove.

By the way, I could get hot water from the furnace---I mean boiler---in the winter, but I'm not going to do that at $8 a gallon for oil. I'm hoping to minimally use the furnace this year.

I misread and thought you'd be turning it off and on frequently—a lot of electronics prematurely fail from constant power cycles.

If you keep your WH on a timer once a day to bring the temp up, the only savings would be temp. maintenance power which, as others alluded to, is not much at all.

If it's off for a while, however, then you're definitely going to save money (minus the costs for heating cleaning water).

Doing some research, it looks like as long as you heat the tank up to the right temp before using it after it's been cool for a while, it should be safe.

I might still use the "hot" periodically just to get some fresh water through there, but what I would NOT do is get into shutoff valves—if by chance the heater runs without enough water, your WH element is junk.

I'd be interested to know how long you have to have it off before noticing a decent savings.

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[brk-lnt]

A more reasonable approach would be to replace your water heater with a smaller capacity unit so that you are not heating so much water. Add a timer so that the heater is only heating water when are awake and you might eliminate 100 hours of heater run time in a month.

Depending on where your water heater is located, the heat loss (other than in summer time) may not be as much of an issue as you think. If it's in a part of the house that you heat anyway, then the heat loss from the water heater is offsetting runtime from your furnace. Granted it may not be a 1:1 factor, but it also might not be large enough to be a major factor.

[brk-lnt]

Originally Posted by thinkxingu

I'd be interested to know how long you have to have it off before noticing a decent savings.

Larger (30gal+) water heaters are usually 4000-5000W. Let's say 4500W on average. Your electric rate is based on Kilowatt hours, or using 1KW for 1 Hour. 4500 = 4.5Kw. Multiply your full electric rate by 4.5, and that's how much it costs to run your heater for an hour.

If that rate is 20 cents, then an hour of operation is 90 cents, for example. Of course it's not running the whole time, but if you can eliminate 2 hours of heater run time per day that can add up to $54.00/month, or less than $2/day.

[thinkxingu]

Originally Posted by brk-lnt

Larger (30gal+) water heaters are usually 4000-5000W. Let's say 4500W on average. Your electric rate is based on Kilowatt hours, or using 1KW for 1 Hour. 4500 = 4.5Kw. Multiply your full electric rate by 4.5, and that's how much it costs to run your heater for an hour.

If that rate is 20 cents, then an hour of operation is 90 cents, for example. Of course it's not running the whole time, but if you can eliminate 2 hours of heater run time per day that can add up to $54.00/month, or less than $2/day.

Right, but now the calculation is how long to "catch up" to 120 degrees vs. what it would have cost to keep it there for that couple hours.

The same thing applies to heating/cooling homes: that sometimes it's cheaper to keep them at one temp rather than have to cool down/warm up a warmer/cooler house.

The calculations, of course, depend directly on how long the appliance would not be used, which is why maybe vacation mode—7 days off/the whole summer for Sailin—may actually work *if* bacteria's not an issue if warmed back up before use.

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[SailinAway]

Originally Posted by thinkxingu

What I would NOT do is get into shutoff valves—if by chance the heater runs without enough water, your WH element is junk.

If the shutoff valves on the water heater are open, then I'm drawing water from the COLD water heater for the shower. Legionnaire's bacteria is spread by aerosol when it comes out of the shower head.

Under what circumstances would the water heater lose water? Does it depend on pressure from the town water inlet? Like when the town water pipe freezes, the water in the boiler backflows? That has happened to me twice (frozen pipe at the road and cracked water main down the street). Scary.

[John Mercier]

You should only draw from the water heater if the hot valve is open in the shower or faucet.

If you do open the hot side, that should flush the system enough to keep the bacteria count from exploding. The only real value to that is that well water is cold, and the tank would slowly warm to ambient temperature without the use of electricity by drawing heat from the ambient air.

So the tank water would be warmer than the well water.

[thinkxingu]

Originally Posted by SailinAway

If the shutoff valves on the water heater are open, then I'm drawing water from the COLD water heater for the shower. Legionnaire's bacteria is spread by aerosol when it comes out of the shower head.

Under what circumstances would the water heater lose water? Does it depend on pressure from the town water inlet? Like when the town water pipe freezes, the water in the boiler backflows? That has happened to me twice (frozen pipe at the road and cracked water main down the street). Scary.

Yup, with your mixing valve you're right.

If you had a shutoff after the water heater, you'd be fine. I was mostly referring to one before, which would prevent the water heater from filling if any were lost. Just not worth it given the potential damage to the tank.

It sounds like if you're willing to shut it off for a while with a shutoff to keep the water heater water from mixing with the straight cold you might save a few bucks.

I'd really like to know if it's worth all the rigmarole, though, after calculating costs to heat from cold, heat cleaning water, and always cold showers.

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