Truth About Switching Geysers Off?

Arthur said:
Not really. If you use the same amount of hot water, it takes the same amount of energy (hence units of leccy) to heat it. Usage aside, leaving your geyser powered on only replaces the energy lost through dissipation, which is a function of how insulated your geyser is.

People who report savings are getting them mostly by reducing their hot water usage, and that saves energy. If the number of hot litres stayed the same, you wouldn't really measure any appreciable saving.
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Another cause of 'saving' is that postpaid accounts may be for differing periods. My Cape Town council can vary between 25 and 60 days of actual (vs estimated) readings.
 
so ....

we are still at ...

anecdotal evidence for turning it off vs the mathematically inclined who swear it either doesn't save or uses more .... SIGH ...
 
Zoomzoom said:
so ....

we are still at ...

anecdotal evidence for turning it off vs the mathematically inclined who swear it either doesn't save or uses more .... SIGH ...
Click to expand...

I suppose it depends on the size of the tank, the location of it, insulation... what else? I suspect most of the time this is not taken into account and causes random results.
 
access said:
I suppose it depends on the size of the tank, the location of it, insulation... what else? I suspect most of the time this is not taken into account and causes random results.
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The only accurate way would be to measure hot water usage and geyser electricity usage simultaneously. The latter is easy with an Owl or equivalent, the former would probably require installing a water meter on to the hot water outlet on the geyser.
 
emptybruwer said:
I am saving about R300 pm after installing n timer. I highly recommend getting 1
Click to expand...
Possible. But the saving is because you are using less hot water, not because you have a timer. The timer might well make you more conscious of hot water usage and thereby change your nett monthly usage. But there is no way on God's green earth you can use less energy heating the same amount of water.
 
Arthur said:
Possible. But the saving is because you are using less hot water, not because you have a timer. The timer might well make you more conscious of hot water usage and thereby change your nett monthly usage. But there is no way on God's green earth you can use less energy heating the same amount of water.
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One possible way of using less electricity would be to switch off the cold water inlet so as to maintain the temperature of the water in the geyser. Once you have finished using hot water, the cold water inlet could be switched on again and the geyser water allowed to heat up. That way water flowing through the geyser would not be heated, only that which is retained in the geyser for heating.

Speaking of inlet water, it the temperature of water entering the geyser varies significantly at different times of day, then only filling the geyser when the inlet water temperature is high would definitely help as tis would decrease the water differential. So maybe the best way to achieve savings would be to have an insulated tank from which the geyser is filled?
 
Arthur said:
Possible. But the saving is because you are using less hot water, not because you have a timer. The timer might well make you more conscious of hot water usage and thereby change your nett monthly usage. But there is no way on God's green earth you can use less energy heating the same amount of water.
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This! Proper use of running hot water taps are the key
 
I tried turning it off during the day.

Was annoying AF when I needed to have a shower after exercise in the evening and didn't save anything on electricity.
 
emptybruwer said:
I am saving about R300 pm after installing n timer. I highly recommend getting 1
Click to expand...
That does not compute with me , since R300-400 pm is what i save with a solar geyser with a geyser wise timer connected
 
Think about it for four femtoseconds:

Energy goes into your geyser via the heating element. You can safely ignore other ways energy gets into the water in you geyser, such from the atmosphere (via the geyser housing), various extraterrestrial radiations (eg sunlight or beta/gamma radiation from space) - none of these are significant for our purposes.

Energy leaves your geyser in one of two ways: 1. with the hot water you use, and 2. heat-loss through dissipation, which is a consequence of less-than-perfect geyser insulation.

Let's assume your household uses 3000 litres of hot water per month, at 60 degrees C. Let's further assume that the incoming cold water has an average temperature of 20 degrees C. That means your household needs to raise 3000 litres of water by 40 degrees Celsius in the month.

Now, it takes 4.187 Joules to raise one millilitre of water by one degree Celsius. So 1000 ml takes 4.187 J x 1000 = 4.187 kJ. So, to raise 3000 litres of water by 40 degrees C takes 3000 x 4.187 kJ x 40 = 502 440 kJ. That's it.

Here's the thing: It doesn't matter whether you do that temperature raising over an entire month or over an hour, it takes exactly the same amount of energy.

Since the only possible ways energy leaves your geyser is 1. with the hot water flowing out through the pipe and to your taps, or 2. via dissipation/heat-loss to the atmosphere through the geyser housing (affected by geyser insulation), the only possible way you can make a saving in your hotwater heating bill is by: 1. using less hot water, or 2. heating it less, ie to a lower temperature (turn down the geyser thermostat, but dangerous as mentioned), and 3. insulating the geyser against losses through dissipation.

Those claiming savings by fitting a timer or switching off are in reality using the timer as a psychological aid to reducing their nett monthly consumption of hot water. There is no other possible way in the known universe that your bill can be reduced.
 
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Oh, I must add that that the nett monthly costs can change in the foreseeable future - when electricity resellers (such as your municipality) introduce time-of-use tariffs. Currently, no SA municipality has TOU tariffs for domestic users. But it is national policy to abolish the current Inclined Block Tariffs (IBT) and introduce TOUT (Time Of Use Tariffs).

Once TOUTs are introduced, it can make a lot of sense to shift your energy consumption to lower-tariff times. That's where timers can help.

But right now, they do nothing for energy savings, other than perhaps help you reduce your nett monthly hot water usage, a psychological device causing attitude change causing behavioural change. Still useful at the end of the month, but the change is in you, not the hot water heating system.
 
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Fuzzbox said:
So if you were saving 8 units a day @ lets say R2 per unit.
That amounts to an approximate saving of about R480 per month.
That is a meaningful amount.

Also when a geyser is turned off it takes about a day to cool down because they are pretty well insulated.

I have been turning my geyser off for about 10 years.
They geyser was accounting for about 30% total usage.
Went from about 1100kw per month to an average of about 850kw per month.

Geysers also dont have to be set to 65 degrees when 55 degrees is still damn hot.
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Not got enough to kill bacteria growing in your geyser
 
Everyone says: said:
...it does not make difference...
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Tried myself, I have prepaid electricity, so I have at least some concrete numbers.

It saves only 2-3KW a day with blanketed geyser (in spite of that, geyser cools downs to luke warm in 24 hours), provided geyser is used once a day in the morning.
 
Arthur said:
Think about it for four femtoseconds:

Energy goes into your geyser via the heating element. You can safely ignore other ways energy gets into the water in you geyser, such from the atmosphere (via the geyser housing), various extraterrestrial radiations (eg sunlight or beta/gamma radiation from space) - none of these are significant for our purposes.

Energy leaves your geyser in one of two ways: 1. with the hot water you use, and 2. heat-loss through dissipation, which is a consequence of less-than-perfect geyser insulation.

Let's assume your household uses 3000 litres of hot water per month, at 60 degrees C. Let's further assume that the incoming cold water has an average temperature of 20 degrees C. That means your household needs to raise 3000 litres of water by 40 degrees Celsius in the month.

Now, it takes 4.187 Joules to raise one millilitre of water by one degree Celsius. So 1000 ml takes 4.187 J x 1000 = 4.187 kJ. So, to raise 3000 litres of water by 40 degrees C takes 3000 x 4.187 kJ x 40 = 502 440 kJ. That's it.

Here's the thing: It doesn't matter whether you do that temperature raising over an entire month or over an hour, it takes exactly the same amount of energy.

Since the only possible ways energy leaves your geyser is 1. with the hot water flowing out through the pipe and to your taps, or 2. via dissipation/heat-loss to the atmosphere through the geyser housing (affected by geyser insulation), the only possible way you can make a saving in your hotwater heating bill is by: 1. using less hot water, or 2. heating it less, ie to a lower temperature (turn down the geyser thermostat, but dangerous as mentioned), and 3. insulating the geyser against losses through dissipation.

Those claiming savings by fitting a timer or switching off are in reality using the timer as a psychological aid to reducing their nett monthly consumption of hot water. There is no other possible way in the known universe that your bill can be reduced.
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Why?

You telling me that you can't see me saving money by having my geyser on only 4 hours of the day (off 20 hours). I save 20 hours of the geyser going on and off every few minutes.
Also, why would a strange man on a forum lie to you.....:erm:
 
Zoomzoom said:
so ....

we are still at ...

anecdotal evidence for turning it off vs the mathematically inclined who swear it either doesn't save or uses more .... SIGH ...
Click to expand...

Turning off your geyser will save you money, but not the amounts claimed here. You will only save on the electricity to maintain your temperature. If your geyser is insulated well enough, then I wouldn't bother. My old geyser would draw heat up 3 times a day for about a minute. That is 3*1/60*4 = 0.2kWh a day (4kw element) (1/60 is to get to kWh). That works out to 6kWhs a month on maintenance, which for me currently will be charged at R1.43 which is about R9 saving in a month. And that was a cheapish geyser of about R2000. I would not switch off my geyser for just R9 a month.

You have though stated that your geyser cools off quite quickly. So that means your geyser is really badly insulated. So it might save you more money to switch off.

I now have a solar geyser with an intelligent timer, that checks the heat in certain bands. If it needs heating up then it will.

The people saving more are in all probability only doing so because the water they are using are not at the same temperature than they would have gotten if they maintained the heat. So they are essentially using colder water. But if they are not noticing it or are fine with a slightly colder shower etc then it is also fine, but they could have just turned their heat down on the geyser for the same effect.
 
A rough RoT is that a regular domestic geyser can lose up to 1 deg C per hour through dissipation. This can be cut in half through decent insulation.

But remember: Switching off during the day doesn't take away the requirement for that loss to be made up when you switch it on again in the evening.
 
Arthur said:
Not really. If you use the same amount of hot water, it takes the same amount of energy (hence units of leccy) to heat it. Usage aside, leaving your geyser powered on only replaces the energy lost through dissipation, which is a function of how insulated your geyser is.

People who report savings are getting them mostly by reducing their hot water usage, and that saves energy. If the number of hot litres stayed the same, you wouldn't really measure any appreciable saving.
Click to expand...
I think the people who say they are getting savings must be turning of the geysers before they refill, that way they don't heat up a cold tank only to let it cool again. Way too much effort when it's actually damaging the geyser.

I have seen so many tests with proper scientific equipment that show its not going to save a cent
 
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