Electric water heater: OK to turn it off?

upthesaukee · 08-02-2022, 01:04 PM

Quote:

Originally Posted by XCR-700

No I have a gas tankless hot water heater and it works flawlessly well.

Never heard of an electric tankless, I dont doubt they make one, but thats not what we have.

Google them. They do make them.

Dave

thinkxingu · 08-02-2022, 01:10 PM

Quote:

Originally Posted by upthesaukee

Google them. They do make them.

Dave

They're not nearly as common because they lack the speed and efficiency that make on-demands valuable.

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John Mercier · 08-02-2022, 03:45 PM

They actually have great speed and efficiency.
But they require an amount of power that generally results in a service and panel upgrade.

thinkxingu · 08-02-2022, 04:10 PM

Quote:

Originally Posted by John Mercier

They actually have great speed and efficiency.

But they require an amount of power that generally results in a service and panel upgrade.

When we researched them a couple years ago, very few could maintain more than 3gpm, which wasn't enough to do two things at once. They also took incredible amounts of power (the increased service requirements you mention) and took longer to heat, leading to wasted water.

The long-term reliability of electric on-demands was also reportedly lower, which meant the lifespan was shorter.

Things certainly may have changed.

Point-of-use electric on-demands were usually rated much higher, but that opened a different can of worms in terms of install costs, multiple units, etc.

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John Mercier · 08-02-2022, 06:00 PM

The heat is instant... why we call them ''on-demand''.
The gallons per minute that they can deliver is based on the temperature rise needed and the wattage of the appliance.

While this link shows ''up to'' gpm; in general, for our area using well water would require the two bigger models for most homes... and if you undersize... you deal with it; while if you oversize... the unit just costs a bit more rather than take a lot more energy as the internals make up the difference.

https://www.amazon.com/Rheem-Tankles...1MR7Z39V&psc=1

At the bottom comparison, you would see the 18 and 24. The data on the package is much more specific as to flow rate based on the required rise in temperature. Both would likely need a service and panel upgrade.

I doubt when compared to a tank water heater that they would have a shorter lifespan or more energy consumption based on equal usage.

It is just not the way that I would go.
The cost of removing a functioning water heater, possibly moving it to a new location, and the upgrades would take quite some time to recoup when only the standby loss is taken into consideration. A simple time, or shutting of the breaker for longer periods, would cost less and create a large percentage drop in the standby power usage.

LikeLakes · 08-02-2022, 10:31 PM

I don't understand why running the hot water heater for a few hours a day on a timer or switch saves much, if any, energy.

Leave it on, and it maintains the temp you have it set for. Temp drops a bit and it comes on, in a 2 element unit (many are) only one element comes on.

Turn it off for 12 hours and turn it back on, you are asking it to heat water from whatever it has dropped to back up to temp, using a longer run of the element and likely kicking in the 2nd element.

And finally, if you use some of the hot water when the heater is turned off, you are later heating from room temp to set temp since you pulled much of the residual heat out by using the water.

I'm not following the logic. I still say, make sure it is well insulated, and leave it on. JMO.

John Mercier · 08-02-2022, 10:43 PM

For two reasons... she is talking about shutting it down for the season, not a few hours.
And secondly... when cold water is pumped into a tank and allowed to set... it will draw ambient heat from the room (the one you are trying to cool) and warm up to the point of reaching ambient temperature.

Since the heating elements would be shut down for months... and the tank would gain heat while cooling the space... she gets water at maybe 70F without any cost to her... while also losing heat in the space.

LikeLakes · 08-02-2022, 10:58 PM

Thanks for that explanation John. I guess I get it with the complete shut down, but multiple people have talked about switches and timers that run the heater for a period of time each day and I guess I question the real savings of that. I admit I get mixed up between this thread and the "substantially reduce" thread so maybe it was mentioned in the other thread.

John Mercier · 08-03-2022, 07:21 AM

Timers work in a different way.

It basically takes the same amount of energy to heat X number of gallons quickly, but at various times of the day, using the tankless systems... as it does to heat the same number of gallons slowly using the tank systems.

The tanks systems must maintain the temp through extra standby usage; but if used all at once the difference between tank and tankless would be meaningless.

The tankless version just allows more flexibility in the timing of the use.
While the timer tank version has to be used when ready and not allowed to set.

thinkxingu · 08-03-2022, 12:43 PM

Quote:

Originally Posted by LikeLakes

Thanks for that explanation John. I guess I get it with the complete shut down, but multiple people have talked about switches and timers that run the heater for a period of time each day and I guess I question the real savings of that. I admit I get mixed up between this thread and the "substantially reduce" thread so maybe it was mentioned in the other thread.

I was thinking the same as you initially, but it would be interesting to know how long the tank would have to be off to break even and save money.

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08-02-2022, 03:45 PM	#3
John Mercier Senior Member Join Date: Jun 2021 Posts: 3,022 Thanks: 2 Thanked 530 Times in 436 Posts	They actually have great speed and efficiency. But they require an amount of power that generally results in a service and panel upgrade.

08-02-2022, 06:00 PM	#5
John Mercier Senior Member Join Date: Jun 2021 Posts: 3,022 Thanks: 2 Thanked 530 Times in 436 Posts	The heat is instant... why we call them ''on-demand''. The gallons per minute that they can deliver is based on the temperature rise needed and the wattage of the appliance. While this link shows ''up to'' gpm; in general, for our area using well water would require the two bigger models for most homes... and if you undersize... you deal with it; while if you oversize... the unit just costs a bit more rather than take a lot more energy as the internals make up the difference. https://www.amazon.com/Rheem-Tankles...1MR7Z39V&psc=1 At the bottom comparison, you would see the 18 and 24. The data on the package is much more specific as to flow rate based on the required rise in temperature. Both would likely need a service and panel upgrade. I doubt when compared to a tank water heater that they would have a shorter lifespan or more energy consumption based on equal usage. It is just not the way that I would go. The cost of removing a functioning water heater, possibly moving it to a new location, and the upgrades would take quite some time to recoup when only the standby loss is taken into consideration. A simple time, or shutting of the breaker for longer periods, would cost less and create a large percentage drop in the standby power usage.

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08-02-2022, 10:31 PM	#6
LikeLakes Senior Member Join Date: May 2021 Posts: 339 Thanks: 50 Thanked 92 Times in 66 Posts	I don't understand why running the hot water heater for a few hours a day on a timer or switch saves much, if any, energy. Leave it on, and it maintains the temp you have it set for. Temp drops a bit and it comes on, in a 2 element unit (many are) only one element comes on. Turn it off for 12 hours and turn it back on, you are asking it to heat water from whatever it has dropped to back up to temp, using a longer run of the element and likely kicking in the 2nd element. And finally, if you use some of the hot water when the heater is turned off, you are later heating from room temp to set temp since you pulled much of the residual heat out by using the water. I'm not following the logic. I still say, make sure it is well insulated, and leave it on. JMO.

08-02-2022, 10:43 PM	#7
John Mercier Senior Member Join Date: Jun 2021 Posts: 3,022 Thanks: 2 Thanked 530 Times in 436 Posts	For two reasons... she is talking about shutting it down for the season, not a few hours. And secondly... when cold water is pumped into a tank and allowed to set... it will draw ambient heat from the room (the one you are trying to cool) and warm up to the point of reaching ambient temperature. Since the heating elements would be shut down for months... and the tank would gain heat while cooling the space... she gets water at maybe 70F without any cost to her... while also losing heat in the space.

08-02-2022, 10:58 PM	#8
LikeLakes Senior Member Join Date: May 2021 Posts: 339 Thanks: 50 Thanked 92 Times in 66 Posts	Thanks for that explanation John. I guess I get it with the complete shut down, but multiple people have talked about switches and timers that run the heater for a period of time each day and I guess I question the real savings of that. I admit I get mixed up between this thread and the "substantially reduce" thread so maybe it was mentioned in the other thread.

08-03-2022, 07:21 AM	#9
John Mercier Senior Member Join Date: Jun 2021 Posts: 3,022 Thanks: 2 Thanked 530 Times in 436 Posts	Timers work in a different way. It basically takes the same amount of energy to heat X number of gallons quickly, but at various times of the day, using the tankless systems... as it does to heat the same number of gallons slowly using the tank systems. The tanks systems must maintain the temp through extra standby usage; but if used all at once the difference between tank and tankless would be meaningless. The tankless version just allows more flexibility in the timing of the use. While the timer tank version has to be used when ready and not allowed to set.