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Does switching off your geyser really save electricity?

Moneyweb Community member says it is a myth.

Admittedly, it’s a popular myth that switching off your geyser saves electricity as Gareth Cotten discussed in How to save on your electricity bill and it’s even propagated by government, but it’s completely false and it’s inexcusable that a reporter does not check his facts before claiming a cited obvious, but bogus method of saving electricity. The fact is that in a properly insulated geyser the heat energy is well contained and the only possible source off loss is the tiny amount that escapes the insulation during the day. While the geyser is on during the day and no water is consumed, a small amount of electricity is used to replace this heat loss – the thermostat typically switches on for two minutes once every two hours (measured on my own geyser) representing a daily extra consumption of around 50 Watts or around R30 of energy costs a month! Anything you do to a geyser can only save a fraction of this amount – the rest is actual energy used to provide hot water actually consumed and you cannot do anything about that.

The fact is that by switching off the geyser, water is allowed to cool further than usual so that when you switch it on again, it takes as much energy to reheat the water to its original temperature than it takes to keep it at that temperature in the first place – it’s called the law of conservation of energy and is an inviolable law of nature. What confuses the matter, is that a small saving is actually possible because the rate of heat loss falls as the water cools – this is, however, a second order effect that on a daily cycle has almost no effect. If you leave the house for a few days, yes – because once the water reaches room temperature there can no longer be any energy loss. I have carefully measured my own geyser behaviour (family of six) using an electricity power data logger – the saving is at best about 2% if you switch the geyser off overnight. This is supported by studies done at the University of Pretoria, available to any reporter. The best you can do is buy a geyser blanket and even with that the small savings you make it will take about a year to pay for the cost of the blanket.

*Arnold Theron is an engineer and member of the Moneyweb Community

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Well, this is just peachy, considering we spent a small fortune getting a solar geyser fitted. What are effective ways to save electricity, then? I’ve got a gas stove and oven — what else can I do? Less kettle boiling, dishwasher and dryer action?

Saving R30 a month is for poor people. Join the ANC, get involved in a BEE deal – feed at the trough – get rich by doing nothing (really) – then you never have to bother again about trivailities like household power bills.

surely if you have insulated your geyser using a geyser blanker, the water temp does not drop substantially.

therefore, you can run your geyser for say 2 hours a day and you save power as the water temp has not dropped that much to require it is reheated from a very low temperature.

this seems to have worked well for me.

Well, I see your point of view with a family of 6. Im assuming that there is someone on the property 24/7. That being a domestic while you and the kids are away at work/school or a retired parent living with you & at home during the day.
In my case, a family of three, married couple and a mother in law staying on the property in own cottage.
I installed timers on geyser and put the blanket on etc. Mother in law as with us are not home during the day, 8am to about 5pm.
Turing the geyser on for 2 hours a day 16h00 to 18h00 (outside peak hours) & stays off the rest of the day and night. Winter it increases to 3 hours 06h00 to 07h00 and 16h00 to 18h00.
This brought our electricity consumption down from R580 odd per month (excluding the fixed municipal charges) to R365. We have had this system for over a year and I keep track of monthly usage (not to a point of knowing what the gyeyser uses exactly) but keeping all variables like cooking, lighting, washing etc within standard daily activity. We fluctuate about 50kw every month.

So the savings have been well over 30% per month.

I back tested it by turning off the timer and seeing what the effect would be last November (2009) and found the usage jumped to the orriginal. Our bill for that month with the new prices was R648. Savings depends on use I guess.

If people are so concerned about the technicalities of saving electricity as they clearly are, simply shut down the geyser and wash with cold water. For sure you won’t have the stress of getting so technical about rands and cents.

You talk absolute rubbish. I fitted a timer switch on my geyer and it saved me 45% of my electricity bill.

What seems to be missing from the article is that by installing a solar heating system you need not use any electricity for very long periods of time. Collleagues of mine have gone for two years now without using any electricity for water heating. None. Nada. This is a substantial saving, but is probably not the norm. The latest calculatuions by various bodies show an electricity saving of somewhere around 30%

I have a prepaid meter in my home. I use – 30 units per day (see it on the display). I experiment with to switch my geyser off in the morning and on when I get home in the afternoon. The units drop to 26 but when I switch the geyser on it uses 4 to 5 units to warm up again. My final conclusion I leave it on.

There are many examples of people testing this – just search online. You’ll find that experiences differed. If that’s true then if *some* have found benefit, then it’s worth finding out what those people did and testing it yourself.

For example, assume your geyser is off during peak hours, then in some countries you get lower charges for the same effort of maintaining a given temperature. That can make the difference all by itself. Others said that they played with the time patterns and some were more effective than others.

I’ve also heard many times that switching the temp down a few degrees is hugely beneficial, as the difference between inside and outside the geyser is reduced. The geyser also doesn’t have to do the work of getting the water than extra few degrees hotter, every time.

Microwave coupled to solar. Switches on, on demand. No 200l heating by electricity. Just solar and microwave to give it the extra couple of degrees as you need it??

I agree – Malema and Zuma proved you dont need an education to become rich beyond your wildest dreams, all courtesy of the honest tax payer who does an honest day’s work. And if you have shares in the company that supplies Eskom, you will actually make money out of the tariff increases, so its all good.

Wanted power, why for the right to TAX! look at Valli Moosa, Cyril , Tokyo and the rest of the parasites, wealth beyond avarice, now take away the one thing they still crave “RESPECTABILITY” when you see them walking round Hyde Park, swear at them make it clear they are not “RESPECTABLE”

Take my word for it its pisses them off big time.

The reason people are seeing savings when putting in timers is because the temperature in the geyser is actuallly lower than without the timer as the element doesn’t switch on automatically. You have to then add less cold water to the bath/shower. You can get the same saving without a timer if you set your thermostat lower. This will make you use less cold water. No use heating the water to 60-65°C and then adding cold water to get it back to 50°C to bath in…

Yes, there is a saving but it’s insignificant.

The only reason why people report a significant saving is anagolous to the placebo effect in medicine. When people decide to proactivately save electricity, they normally effect a lot of other savings simultaneously, consciously as well as sub-consiously, such as showering instaed of bathing, minimising shower time etc, etc.

By the way, Gareth Cotton is associated with who charge R400 per coaching session! I personally would stay far away from him if this is the level of advice he is prepared to spew out. He should stick to watching the waves.

The article is about geyser timers, not solar. With solar the savings are real, and in the forthcoming years increasingly so.

ur geyser is made to work harder every morning to warm up water that is at room temperature, the element heats up more and for longer. Try this for a couple of months and your friendly electrician will be there in no time to help you replace the element and / or thermostat. I learned the hard way.

I have a geyser timer and is has saved me a lot of money. It is irresponsible to state that it does not work.

My experience – and I am also an engineer – is a significant reduction in our electric energy consumption. My geyser is a fairly new Kwikkot (so should be of standard insulation) and is located in my roof space – which gets quite cold in winter. It is obvious that my energy consumption required to maintain temperature must be more than the 50Watt?? ( Watt is not a measure of energy consumed – I presume he means 50 Watt for 24 hours/day for the full month ie. more or less what a light bulb would consume) which he measured.

It really is not difficult for Eskom to do some accurate trials and give the public the results. Can we get this please Eskom…………

1.Going on holiday ……….YES

2.Nobody mentions the blasted THERMOSTAT …….turn it down in

summer and spring .

3.Don’t you have economy saving times in South Africa …….I guess not all to do with being 3rd world and escom being backward

4.If you live in Natal why would you need a geyser

5.Why not use a Panasonic water heater and only heat the water you use.

(most hotels use them)

6.Don’t use a dishwasher biggest water and energy guzzlers in the house

7.Have more barbques burn up old Sunday Times newspapers

hope you lot find this useful

PS Cut down on your boozing you will get an anual holliday out of that

Dear SOB – dont despair–the solar heater really does save electricity if you switch off the electricity supply to the geyser. It will also give you a nice warm feeling about the environment and global warming. We all gotta do our bit

Bollocks..I put in a Digital Geyserwise and have dropped my 2 x Geyser bill but roughly 50%. I tightly control when the geyser comes on and goes off based on usage patterns. This does take some thought to do it properly – but it works. ( Yep ..a Geyser Blancket will also assist)

The law of conservation of energy dictates that for normal usage patterns, the author is absolutely correct, PROVIDED your geyser is well insulated. Once your geyser is heated, it will only use electricity to replace any heat it has lost, either through use of hot water or loss into the air surrounding your geyser. Therefore, if your geyser is insulated well (as most are) your electricity usage depends ENTIRELY on your hot water usage.

Regarding the theory of lower geyser temperature saving electricity – rubbish… you’re still going to make your shower/bath the same temperature, but if your geyser water is cooler, you just use more of the heated water to give you the same bath water temperature. WHATEVER HEAT YOU USE MUST BE REPLACED.

Of course, if you use your geyser once every few days, you will save electricity by switching off… but you’d probably make up the cost difference in deodorant.“

The will you come clean up the melted water in the kitchen from the defrosted freezer after my holiday?

Well I disagree ,I have done the exercise and it saves allot more than R30.Leaving it off for even two days only ,takes a short period to warm up ,may be less than 30 minutes .I have two geysers and it saves me at least R150 per month.

This article is correct. Turning off your geyser will only save a little extra energy lost due to the reduced difference in temperature between the geyser and outside. (Assuming you have good insulation).

Those who mention large savings achieved from switching off the geyser by day will probably be saving because the hot water consumed during the day will be less hot than normal and they will then be consuming less energy than usual.

This is the best way – bath and shower at a slightly cooler temperature or use less water at the same temperature. Turning down your geyser temperature and bathing at the same temperature only means that you use less cold water. The same amount of energy is consumed.

How the hell can we beleive you, Gareth, you lie, you lie, you lie! Moneyweb get rid of him.

If you add cold water to any hot water you use then your thermostat is set too high and you are wasting energy. The very first action in saving costs should be to reduce the thermostat to about 60c. As for saving by turning a geyser off, I would ask if you should therefore leave your kettle boiling all day just in case you need a cup of coffee?

Arnold, thank you for at least taking the time to write in to Moneyweb to share your thoughts. If only more people could take your proactive approach, rather than hide behind the anonymity of snarky comments…

You may well have the engineering background, but like I said in the comments to my own article, the savings advocated have been personally experienced. Eco Green has a great point in that most households are not quite as big as six members, and the smaller the household, the less likely you are to need hot water during the working day. Having said that, though, everyone is entitled to their opinion – but I’m going to stick with my personal experience, and the 51 votes as of right now that agree with me (might not be the majority, but statistically significant enough for my liking)…

By the way, I do definitely agree with your recommendation to insulate your geyser properly. Many people, especially in older houses, do not have sufficient (or any) insulation on their geysers, and are wasting energy unnecessarily…

I have fitted a Geyserwise timer switch and controller and have made savings of about 30%. But I concede that this could be due to
– simultaneously using controller to find lower acceptable thermostat setting
– generally being more energy conscious around my house
Its certainly not conclusive. But what I have tried to do is to have two windows within which hot showers take place in my house. Say 6am to 9am, and 6pm to 9pm. My timer switches on the power an hour or two before the window starts AND also switches OFF before the window starts so no subsequent and wasted heating takes place when hot water is used.

With the controller pad easily accessible and finely adjsutable, unlike the poorly located and not finely adjsutable original thermostat control on the hwc, I keep reducing the thermostat setting. When people say water is colder, I say use less cold water. My aim is to keep reducing until I get three showers per window using minimum cold water.

Following the thermostat setting argument made by many

– Insulate the geyser
– Insulate hot water pipes
– Turn down thermostat temp

Garbage. I did some thesis work on this some time ago.1 – Normal geyser resting cycle is about 10% which means to maintain temperature, the geyser needs to stay on for 6 mins per hour. 2- Losses are proportional to the difference in temperatue so switching your geyser off results in lower losses. 3 – Mr Theron talks about the conservation of energy which is true as long as you consider the complete system (including the environment). In other words you lose energy to the infinite heat sink of the atmosphere surrounding the geyser. As for the solar panels…….. yours !!!!!

Shower with a friend or spouse, heat water in the microwave for your tea/coffee/cooking and make sure you electrical setup works properly. I was turning my geyser on and off at the main board and the isolator switch ( I think) burnt out because of the power surges. Wasn’t helped by the Jan 08 debacle of course but timers souns sensible. By the way for the uninitiated like me, can one turn the thermostat down yourself or do you need a sparky to do it for you?

I guess my angle was just that its not a proven way to significantly save juice despite popular perception and so should not be promoted as such. There is, however, a lot of comment that claim some savings so as a good researcher one should take due note. There is nothing that replaces actual measurement and good science, though and actually I’m surprised that neither Eskom or any other research house has done the trouble to put out independent and accredited facts that have been properly tested beyond doubt. That would certainly clear the fog for all of us. Congratulations with your votes, though I’m a tad wary of your claim to be supported by statistics as the NO vote is three time the YES vote so far.

You can do it yourself, although you’d need to get into your roof to complete it.

The thermostat is sitting behind a metal plate on your geyser, you can use a small or medium flat screwdriver to turn the small plastic dial down. There are usually markings indicating large numbers, 40..50..60.70..etc.

The thermostat is quite easy to identify as a circular object with a small plastic circular “screw.(usually white)” It’s attached to a thin metal spike that is inserted into your geyser.

I meet them every day in my line of business. This as bricks but had a daddy who could keep them in university for a decade. They eventually passed but understand B*****-all

I too did the switch on and switch off routine, which cost me R 800 times two for two new elements on a geyser that is four years old. So what was saved in electricity, which appears to be minimal from what people are saying, has been eaten by replacing the thermostat and element twice. My electrician and plumber have both said to me it makes little difference. The theory is that you place more strain on the element when it has to work, as it works harder.

A few years ago there was a company that manufactured solar geysers and they advertised that over a period of 20 years a solar geyser would probably save X Rands.

I installed one in the roof of a granny flat and after 7 years the geyser tank had to be replaced.

This would have entailed removing the ceiling in the bathroom in order to remove and replace the tank .Instead a new tank was installed on the roof and it was connected to the existing solar panels.

This tank lasted 3 years and four months.

The quote by the manufacturer to replace this tank about a year ago was approximately R13 000 for a 300 liter tank..

The reason give for this tank failing was because of the quality of water which was supplied by Durban metro.

This solar geyser has been replaced with a 150 liter Kwikhot conventional geyser mounted to an exterior wall where it is easily accessible to a plumber at ground level. Cost of Kwikhot replacement geyser /-R2/3000.

Sorry guys,I dont buy the story that Solar Geysers are that economical to use.

You need to be practical! The 2% loss that was tested in a lab at SABS and not in a house.

In a house you have people tabbing hat water during the day to wash hands, do the dishes, wash the floor, etc. The new colder water that flows into the geyser makes the temp drop much more than 2%. Trust me. I have tested this at home for 12 month.

By switching off the geyser before you go for a shower and only switching the geyser on 2-3 hours before your take the next shower you WILL save 20-40% on your bill!

Everyone’s installations are different. Pipe run lengths from geyser to shower, bath etc. Different insulation quality, thickness and age and whether geyser only or also pipes are insulated. Peoples personal preferences for showers and baths are different in terms of hot, warm, cold.

Turning on and off a geyser will cycle the element and lead to premature failure. The degree to which geyser water will cool is a function of time and how much energy it gives up to the surroundings. There is little to be gained from turning off/on during the day. If you going on holiday for an extended period then yes it may be of benefit in saving electricity (unless its winter, your pipe may freeze and burst).

Adjust your geyser thermostat to a water temperature comfortable for you and insulate your geyser and pipes. Minimizing pipe runs during construction also helps as it minimizes water volume and geyser top-ups that needs to be heated to maintain desired temperature due to people running a bath or shower until warm enough for them.

Just do whatever works for you. It may be working for you in saving electricity but not in the way you have rationalized it.

As for Cotton costing R400 a session…does he do plumbing? only R400 is cheap for a plumber or electrician call out…

I put in a digital Geyserwise system and have reduced my electricity from R800 pm to R450 pm. I am not an engineer but I understand R800- R450 = R350 saving per month. I don’t know how it works but I don’t care – I am saving R350 per month and that’s all that matters. You programme the system once and it is taken care of. ESKOM also installed the blanket on my geyser for free and in less than a year, only pieces were lying on the ceiling!

Gareth Cotton know his subject and providing absolute correct advice. If you know when to switch off you can only gain.Geyser blankets may have negative influence. Without blankets 80 % of the year you may gain temperature as much as 14 degrees C per day on 150 lit capacity. Temperature play the most important role in achieving switch off savings. Without this knowledge at hand you touch in the dark like driving a car without speedometer and fuel gauge.
With geyserwise unit you can now start managing your geyser which contribute 40-60 % of your total bill.
Easily save 30% of your hot water energy requirements.

Considering Geyser timing – If one is using a geyser timer the average temperature of hot water drawn off in the day is lower. i . e when someone does the dishes in mid morning, they are not being served maximum temperature water as would otherwise be the case. At the end os the off cycle more heating needs to be done from daily offtake but mid day user cause a saving because they are getting cooler water. Re Insulation. It all comes down to the efficiency of the insulator and that insulator at any given temperature. A 100% insulation efficiency would only require that the element reheat water that has replaced water used. It would also therfore dictate that any thermostat setting is Ok as there would be no heat loss with 100% efficiency insulation. Conversely if an insulation is 0% effective than the most efficent temperature of the geyser is room temperature as no heat loss would occur. Considering the fact that no insulation is 100% efficient a tendency to set the thermostat to a temperature as close as possible to room temperature is desired. I will be surprised if heat loss dose not increase with due to temperature diffirential. (proof your geyser will use more energy in winter than summer while leaving the thermostat set the same) Conclusion – Efficiency of insulation and differential temperarture.

I can only assume the 51 votes in favor of your bizarre, (tik-induced ?) theories, represented the total no. of Capetonians capable of reading and writing.
Did the waves perhaps whisper these secrets to you during one of your gazing at the sea and talking to yourself moments ?

Zook needs an engineer to back up this theory. Come on where is the formula. Efficiency of insulation of a given material at a range of temperatures . All else is gook with the one exeption of giving mid day users warm water.

…I hope you don’t represent the co. that sells the stuff. If you do, you might want to brush up on your communication skills, ( your analogies are ‘interesting’)— Perhaps you should attend one of Gareth’s Hippie seminars.

For geyser blankets to have a negative influence would require ambient conditions in the roof space to be higher than the set temperature of the geyser. For most geyser temperatures to be warm or hot (depends upon personal preference) settings would need to be 45C and above and roof space an even higher ambient. This is seldom the case although electronics in the roof space such as movement sensor alarms are rated for higher temperatures as its a given that roof spaces will be warmer. The frequency and duration of ambient being higher than geyser water temperature setting would need to be significant to claim the quoted savings. Any technical data source?

Here is a technical source regarding insulation and contains data on roof space measurement temperatures (45C) that also references the six CSRIR defined climatic regions of SA that would influence the variability in performance being encountered by differing community members.

Generic solutions may not produce results to the same extent as specific solutions matched to your home and region.

dude you make me laugh.

Time to consider the theroy of thermodynamics. Any a–hole who advises that it is energy efficient not to switch the geyser off, has little knowledge of thermodynamics. The reasoning is as follows, ie.:-

1. The man presumes that there is no one home most of the day, therefore does take cognizance of the fact that hot water is used in many households throughout the day.

2. Similiarly he fails to recommend that the thermostat be set at 60 degrees C.

3. He fails to motivate why water should be heated long before it is required for consumption which leads to heat losses prior to consumption.

4. He fails to tell us why the water should be heated to such an extent that it is necessary to add cold water to the hot whilst showering.

5. The man fails to take cognizance of the fact that the RSA is much warmer than europen countries, consequently the temperature required for hot water from the geyser in the RSA is much lower than in countries with colder climates.

6. The man must stop doing tests in a laboratory, and do tests in realistic home environments.

7. Lastly does the man work for Eiskom, because they must increase power consumption to turn the utility into a profit making business?

Is it just me, or are the ‘yes’ votes gaining ground?

@ Voortrekker: Ja, schweet, bru, it was totally the water-fairies living in my geyser that told me, bru…

@ Tuscanite: Too true. Like they always say: If you wanna make it rich, don’t become a doctor; become a plumber…

Do all you no. 3-‘Readers’- wearing-engineers realize that if you devoted even a fraction of this time to estabishing the exact location of said G-spot, you would be fiddling around with a far different ‘mouse’ and expending your energies on a far more energy efficient activity. ( With the exception of Capetonians who believe that the ‘G’- spot’ is is is a new bicycle route near Camps bay reserved for intense people in Spiderman outfits.

You could take Gareth’s job.

Ek is 89 maar een ding kan ek van getuig ek skakel al baie jare my geyser af het so 2 jaar gelede een van hierdie nuwerwetse geyser goed gekry wat temperatuur en als wys en ek kan temperatuur stel soos dit my pas. Die ding werk want nou kan ek sien wat gebeur.Van ek die apperaat het , het my krag met nog 4 eenhede ‘n dag gedaal dis soos iemand hierbo se soos ‘n kar sonder spoed en petrol meter jy weet nie hoe vinnig jy ry en waneer om petrol in te gooi. Die geyser is dieselfde jy weet nooit hoe warm water die water is en waneer om aan te sit nie nou kan ek sien.
Om aan en af te sit element beskadig nonsens myne 34 jaar oud sonder probleem.
Vandag se kwaliteit.

Solar panel directly heating the water in the geyser, using a digital timer set to come on at 4 or 5pm for just one hour during the cold months (just 3).
The rest of the year switch off all together and use no electricity at all.
Two 200L cylinders with about 9 years use!

I though Arnold Theron made the most pragmatic common sense conclusions. He did not attempt to present a science paper but merely demonstrates that the saving one may achieve by switching a (WELL INSULATED) geyser off between times of use is only about 2%. Would it really matter if it was 5% on your specific configuration and patterns of usage? I agree with Arnold, it is probably right to assert that it is, in general, a complete waste of time to switch?

That is when you argue on the basis of energy conservation as he does. When we start looking at capital and realistic time of use electricity pricing, (or the implied costs), things become very clear indeed.

The strategy, of limiting energy losses by switching the geyser off between times of usage, does not only guarantee dreadful inconveniency to anyone in the household who dares have a need counter to the geyser cycle, but the likely general switching patterns that are implied would add to the peak load on the national grid and would therefore put strain on generation capacity. It would imply higher generation capacity, or, in the meantime, worse load shedding at the time all these YES votes start switching their geysers on after work. This inefficient use of generation capacity is precisely what Eskom would like to avoid by actually switching your geyser OFF at the very time that the YES crowd want to switch their geysers ON! Alternatively, we may see time of use electricity pricing which will mean that even if in energy terms there is little to be gained by using this switching strategy, in financial terms it will be really counterproductive.

Even if good insulation will limit heat losses directly from the geyser, higher water temperature would cause higher losses in the piping between the geyser and the tap. In winter in particular you may be heating the walls unnecessarily! The precise configuration of your home will determine this loss and the loss will generally be proportional to the distance between geyser and tap. So more geysers closer to the points of use may be a way to save. However, lower geyser temperatures would also imply less mixing with cold water at the tap, which further implies the need for larger geysers, (capital outlay).

Whatever you do please avoid setting the thermostat above 67 degC, as salts are formed above this temperature that cause build up on the element and internals of the geyser.

You want Exdom to tell you what to do i.e. whether the timers will work or not when they don’t even know which end of the plant to put the coal into?

I read the article, and the author is obviously not a power engineer & more

interested in his own finances.

switching of the geyser saves 3kw of demand on the electricity system. if it

is switched off during peak periods, you can imagine how much this saves in

spinning reserves. This affects the total amount of generation that has to

be installed in the country

the timers is set to consume power in off peak periods when it should not

impact on spinning reserves.

Municipalities have installed load control onto geyser to take advantage of

not incurring un necessary max demands, and in this way they have given

domestic consumers a power unit rate. hows that for a saving which was not


I think that consumer who just demand electricity as a right should be

penalised, especially a narrow minded article such as this. his savings may

be true, but the bigger picture has not been considered]]regards


I have the evidence that the geyser switching works – I have records of my electrical consumption since 2006 (before I started switching mine off) and I installed a geyser timer in 2008. Together with other actions I took, my electricity consumptioned dropped by 41%!!!

You could only prove your assertion if you kept all other variable constant? You made all kinds of interventions to save electricity, so which one is it that caused the 41% saving? And how much did switching the geyser contribute to the 41%. Ziltch, nothing, 2% points?

Do you see what C** I am resorted to reading whilst awaiting your normal Thursday Article???


And we thought YOUR readers took themselves seriously….this is truly the geekiest, MOST BORING article, debate…..yawn, sorry I dozed off there…..I AM OUTTA HERE!!!!!

Who cares about the “Does switching your geyser off blah blah blah yawn” button…..where is the DO YOU LIKE THIS AUTHOR button……dude I would so give you a THUMBS DOWN….Hurry Thursday Hurry!!!!

Using a dishwasher uses less energy than washing by hand. Certain.

2 of us in avg suburban home

Electricity usage proir to changes -R800p/m

Installed 150l solar geyser as prefeed

Bought gas stove for cooking

Changed 1.1kw pool pump to .75kw reduced running time

changed to CFL bulbs and all security lights 70w Metal halide or HPS

Capital Expenditure

Current usage <10kwh/day total bill -R350...Priceless

Most unfair of you.

Firstly, Arnold Theron is NOT responding to the switching regime where your geyser is switched off by Eskom (National Control) or municipalities, to smooth power demand during the day. He is very clearly responding to quite another regime promoted by Gareth Cotten in quoted article, in which he prescribes as follows:

.. turn off your geyser for the periods when you’re not at home. .. If you re only using it during the two peak periods (like most people), then turn it off on your way out to work in the morning, then back on when you get home .. then turn it off again when you go to bed, and on again as soon as you wake up..

So Cotton is clearly proposing a regime that will worsen demand during peak periods.

To lower demand for installed generation capacity, it would make sense to switch geysers ON during off peak hours when people are at work and when the Cotton s crowd have their geysers OFF!

When Cotton switches his geyser ON is when we need to run expensive peaking power stations, burning oil and diesel.

The solution is clearly that electricity should be correctly prices for time of use, aND the price set at the balance between supply and demand?

Neither are you right to claim that a (typical) geyser uses 3KW? Theron found, monitoring the behaviour of his own geyser with a data logger, that the thermostat typically only switches on for two minutes once every two hours during the day when no water is consumed, when only a small amount of electricity is used to replace a miniscule amount of heat loss. In aggregate, your 3KW therefore becomes 50W average. It is clear that geysers normally only use the bulk of its power consumption shortly after hot water is used and cold water is required to be heated to replenish consumed heat. As people typically use most of their hot water during peak hours, the saving is clearly to delay switching the geyser on again after use. Because of the dysfunctional power pricing regime, the cost however is not for the consumer directly, but for Eskom.

So Cotton is promoting a regime that may at best be said to benefit marginally from an arbitrage gap due to the misprising of power through an 24h cycle.

The best solution to power wastage is correct power pricing, on time of usage basis.

Does any of this really matter in the big picture of things ? !
Just imagine having some of these contrbutors around for a dinner party.
What normally occupies their minds ? – Where do they all come from ? ! – Is this what a Bsc. degree does to an otherwise normal brain.
Hell, they can’t ALL be Capetonians.

My point exactly ! ! LOLOL!!! Yawn yawn, zzzzzzzzzzz

I am in the process of purchasing a property near a university which will be used to accommodate students.

I am installing SEVERAL solar assisted geysers, in total having rather LARGER CAPACITY than would be the traditional norm, so that I can run LOW TEMPERATURES and have SHORT PIPE RUNS.

Also, it is relatively inexpensive to divide your electricity circuits and install separate electricity usage meters so that you can get a situation where you monitor consumption and where every user pays. That is the best way to transfer responsibility and motivate saving in general.

PS I am told you get Chinese units for as low as R100 a meter, although better units may be closer to R400. Those are the bulky units used by municipalities, but you get smaller meters now that fit in the switch board like a standard breaker, although they are more expensive, apparently closer to R800 a shot.

PPS No interest in brushing up on your science.. Bonita and Voortrekker ?

There is no thermodynamic energy savings from switching off/on a geyser compared to maintaining a constant temperature.

There is a saving in peak load power requirements by moving the power usage to a non-peak period. There is no financial benefit to the consumer unless peak load pricing is part of the contract.


Question: How much is saved?

Answer: The customer does not save anything. The municipality saves by shifting the load from peak times to standard and /or off-peak times and so produces a lower electricity bill to the customer. The amount saved is between R150.00 and R190.00 per switch annually, on the Eskom MegaFlex tariff.


I’m curious to know how well-insulated the average geyser is. It must be very well insulated to keep the temperature drops to only a couple of degrees per hour, which is what’s required to make keeping the geyser on the same price or cheaper than turning it off for 12 hours per day (assuming no hot water is used while the geyser is turned off).

Mr Theron, with regard to the UP research, is this available somewhere, or must it be requested? As an engineer you’re no doubt well aware that what you’ve presented pretty much amounts to anecdotal evidence and a sample size of one doesn’t really provide anything useful other than that more investigation is required.

Please opine on the thermodynamics of first poring the cold milk, and waiting for the coffee to cool down, vs. allowing the coffee to first cool down before adding the cold milk? Which is quicker? An everyday problem to solve with your friends around the coffee table, before moving on to more interesting topics like the latest computer fad? Politics? Shall we rather discuss the latest social scene, or shall we just move on to the girls now?

LOL!!! Why all personal Jackie Boy? Maybe you should have thought a tad longer before you typed that one out…..Now does this look like a website where “Cosmo” girls hang out? It really is not my fault that this is without a doubt one of the most boring blog sites and topics that I have read in an undeterminable amount of time.

You win Jackie Boy ! ! You have proven two things today :

1. You know LOTS and LOTS of big words…ummm like M.A.R.M.A.L.A.D.E.- oh no sorry thats one of mine Anyhoo….

2. You react like a typical man, as soon as everyone is not agreeing with you, nodding their heads up and down and telling Jackie what a clever boy he is, he gets CWOSS and says “Hey you, shut up lady!! Go drink coffee and shop!!!! No women with opinions welcome here!”

How sad……for you.

I would love to get involved in a Battle of Wits with you, but MY daddy taught me that it is not fair to fight people who are unarmed…so I won’t bother you any longer with all my “girlie drivel”…….

I’m trying to get hold of that research because as you rightly say one needs proper representative research – I cite may case simply to demonstrate and at least its a measured result. The research was done a few years ago when I still lectured there but the then head of the centre of new electricity sudies has since left. Will send it to Alec once I get it.

The insulation on a geyser is very good which is why a blanket makes only a small difference. If you touch the geyser outside it hardly feels warm while the inside is piping hot. The actual insulation is rated by the kWh heat loss per day usually printed on the geyser.

1) the higher the difference between outside temp and geyser temp the faster the cooling down will take so the rate of cooling down will decrease as the water cools of to a lower temp but it takes more energy to keep it for example at 70 the whole day than reheating it from 40 back to 70
2) the thermostat turns off and on the whole day each time it takes energy to get the element warm to a temp were it actually warms the water
3) If you use hot water the geyser replace the hot water with cold water that must be reheated to wait until tonight for you to use it again

We fitted a solar heating system to our house some 18 months ago. Best investment I ever made. We save 20-40% on ENERGY per month, depending on season and cloud cover. This i measured over the period compared with previous years same time.Payback period about 18 months at today’s ESCOM prices, will be better in the future..
By the way, I am an engineer, and know how to make the sums.

The girls are the first to complain if the water goes cold, so we keep the thermostat up, but when the girls shower they shower tepid anyway. If we forced the girls to shower cold we could save a lot, but then again they might cut us off in other ways. Perhaps Eskom has to talk with the female population and ask them with nice advertising.

Nothing personal about that one I thought. An engineer once told me, while making me a cup of coffee, that this was an academic question posed at his technicon when he studied mechanical engineering, so try apply science and logic. The question requires application of the same theory discussed above to geysers. And if you still find it uninteresting, once you have solved the problem of course, just change the subject, because Im getting bored myself! No doubt you and Voortrekker throw lekker dinner parties where all share in elevated interests?

Maybe you should take some interest in any incentives which will save electricity in future because if an when the lights go out, you will have to resort to manual operation and not be able to rely on your favourite little electric bedtime toy!

Turning the geyser on at 5h30 am and then off at 7h00 and again at 17h00 – 17h30 has done the trick for me. I have a prepaid meter and have personally monitored the difference, my bill has come down significantly. Since we’re a family of two, it may be true that this might work for smaller families, where other influencing factors can be strictly controlled so as to see the difference.

Who knows? Other than that, I’m going to continue switching my geyser off!

It’s likely that all those who claim to have substantial savings when switching their geysers off, have poor insulated geysers.

“representing a daily extra consumption of around 50 Watts”

This statement is baloney. It doesn’t make sense.

Consumption is measured in ENERGY not power. This can be kJ, MJ, kWH (3.6 MJ).

Likewise watts is unit measuring POWER or energy transfer per time unit dH/dT. Daily consumption of about 50 watts is piffle.

I am seriously worried about the level of SA engineers.

Ummmmmm Max, no say it aint so……did you just make an innuedo to the effect of me going to F%&* myself ? ?

LOL my sweetie….my FAVE bedtime toy is battery operated doll!!!! Did’nt know you could get electric toys, but SHOT!!! Thanks for the heads up, I’ll be sure to ask the salesMAN at the “adult” shop for one of those next time hehehe….and actually, lights on or off does’nt faze me!!!!

We have THE lekkerste jolls!! You are most welcome anytime!

This is absolutely correct in technical terms. It indicates that the geyser uses, on average, 50W to maintain temperature, or the other way of looking at it, is to say that the loss of heat through the insulation was at 50W. This indicates a rate at which energy flows. To calculate units of energy over a specific period, you now need to integrate over that period, or simply put, multiply a constant power rating by the time difference.

Is it not correct to speak of consumption as the rate at which a commodity is depleted, like 8.5l/100km fuel consumption? Neither is it wrong to say that i consumed 100litres of fuel to drive from JHB to CPT? Both forms are considered correct use of technical English.

How difficult is that, Lord Max? I do not think the author is technically wrong in any of his units? This is basics? Get your engineering sorted man.

… until 9 o’ clock yesterday when all this started. Then I saw for myself what too much science can do to decent, honest, normal souls. Some of the contributors above would without a thought bludgeon each other to death over a 50 watt disagreement. With nostrils flaring like ones possessed they press on and on and on in a frenzy of bewildering terms and laws.- All over a hot shower and sixpence worth of electricity ! This is scary stuff. – Better and healthier to join Gareth watching the waves,- far less stressful.

I have two brilliant brothers and have worked in highly technical fields myself, and always the same thing. Engineers willing to destroy their profession by, as you say, bludgeoning each other over no turf at all, and in the process even sacrificing science itself. Nothing wrong with a good philosophical debate about scientific arguments, but the way some guys go for the throat makes me just move along to deal with businessmen who actually want to create something great. Unfortunately, the engineers just get dragged along. Their behaviour has disqualified them as builders. They now occupy small offices, in grey buildings, fighting amongst each other for meagre salaries at the lowest levels of management structures amongst the lowest levels of professional rungs, while in progressive countries like China, they are building a great future and even lead governments. I think more than 90% of government officials in China are engineers. Maybe not a bad message to our engineering friends.

C u @ Bonitas!

It is fantastic to see such a debate on this issue and the correct answer is of course: “It depends . . .” And what it depends on most is the usage profile in the house. The only savings to be had, and there Arnold is correct, is the standing losses, i.e. the heat you loose after the water has been heated again to full temperature. If your geyser is not insulated, stands in an cold area, such as outside, and stands for a long time between warm water usages there may be a significant saving, as much as 10% as reported by some above. But it can also be as little as a few percent.

Where most of the savings can be had, and this will be much more through behaviour change than switching off is to merely wash your hands with the cold water from the cold tap and not the cold water from the warm tap. If your geyser is far away from the basin then there will be significant losses in the pipes of the warm water remaining in the pipe after your turned-off.

Lastly, Eskom’s SWH subsidies were doubled last month, so go out and install as SWH today as the savings will be worth your while in the long run with the anticpated increases in the price of electricity.

Never ask an engineer a question or about how something works……………because he will tell you the answer, correctly and in detail.

The circuit breaker size watt hour meter you are talking about is available for about R500 at most electrical wholesalers, is the one I used for my “switch” experiments and is made in RSA

I install them in all my multiple residence propertys to prevent arguments about the electricity bill, Water meters of similar accuracy are available for about the same price at plumbing wholesalers, I have installed them as well.

The method I use (as electricity and water are charged for on a sliding scale by municipality’s) is to take the entire bill and devide it proportionaly amoungst the users according to their meter readings.

P.S. for all the I Thinks, before you can manage something first you must measure it ;D

From the above two articles it seems to me most of the posters are either techies or bookeepers,

Im techie myself who are the bcoms? who are the engineers?


Why? Because every time the geyser switches on, it uses the equivalent of 50 light bulbs! Leaving your geyser on, will cause it to switch on and off about about 24 to 30 times a day to keep a contstant temperature of say 60 degrees. Substantially more efficient (as illustrated by the witness accounts) are to install a timer switch from 4-8 am and 4-8pm. The energy difference is not caused so much by the loss of heat (as Arnold pointed out), but rather by the constant switching.

“representing a DAILY extra consumption of around 50 Watts”

My question: exactly what has DAILY got to do with it? What’s the difference between a daily extra consumption of 50 watts, an hourly extra consumption of 50 watts or simply an extra consumption of 50 watts?

I’m beginning to think that maybe the English on this forum is worse than the science. The daily extra consumption is, one presumes, 24*50 watt hours or just over a kWH (one unit)

To use your analogy my car would have a DAILY consumption of 8.5l./100km. Absolute tripe. My DAILYconsumption is about 2 liters- to work and back.

You cannot defend the indefensible. Keep digging mate, keep digging. You may find some geothermal sources at the rate you are going.

so let us agree that this was a slip of the pen?

Just tell me where and when……. ! !

Have a super day chaps

Good on ya mate. You have a rare quality.

Anything with a heating element will use the most electricity – geyser, washing machine, dryer, stove, kettle. Simple rule: DO NOT USE THEM IF AT ALL POSSIBLE.

3 main things that will have the most influence on how much electricity your geyser uses:

1/ The effectiveness of the insulation – the lower the rate of heat loss the better.

2/ The volume and entry temperature of the replacement water.

3/ The maximum temperature setting. The lower the difference between ambient and water temp the better.

All 3 are in a dynamic relationship.

So Step 1 is too set your max temp to 60degC or so – anything above what is painful to the touch is generally to high – 40C

Step 2 is to add extra insulation at least 10cm thick around the outside, altho the thermal insulation is regulated by SABS standards and is good.

Step 3 is to install an aerated shower head which uses less water volume per unit of time, which means less cold water volume entering the geyser to be warmed up to max.

Step 4 install a timer switch to switch on the geyser only long enough to top up the temp to max.(30 to 90 mins depending on volume) so that you don’t have to remember to do it manually.

Step 5 USE COLD WATER FOR EVERYTHING EXCEPT BATHING. Boil a litre of water in the kettle for the dishes etc.

Step 6 turn off any unused geysers

I installed a timer switch on both my geysers – and it is saving me about 40% of my electricity bill….I suppose every household (size, occupants, when hot water is required is different), and it was some trial and error for me, but after a while you find the right balance….but it DOES work, if you give it proper thought and “tune” it over time.

my account has been cut by almost R200 a month ie by switching it on and off ie round once a day depending.

then again at my parents place they never switch of theirs and they their account is still much less then mine. so why the heck is mine costing me so much. furthermore i think my element is gonners. so i’ll have that checked out.

oh and i have timer switch, which never helped till i switched the darn geyser totally on/off each day.

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