Switch your geyser on and off ! – Does it save me money or not ?

February 14, 2013 in Uncategorized

This is a question that gets asked more often than not, especially on our site visits to potential clients.. Do we save any money by switching our geyser off during day time ???


Well the crew at GESS Green did a wonderful job of explaining it , so I copied the article for you to read.

Your geyser – does it help to turn it off and on?

I can’t count the number of times I have had questions about the advantage of manually controlling a hot water geyser, in other words, to turn the geyser power off during the day and turn it on again in the evening. So I decided to properly investigate this issue, and hopefully shed some light for those of you who have also wondered about this.


A brief explanation of how your geyser works is necessary here for the “not-so-technical”.  Your geyser is basically a big kettle –  a container with an electric element inside. A geyser also has a thermostat, which is a device which continuously tries to keep the water inside at a specific temperature – a temperature which can be manually set. So if your thermostat is set to 60 degrees, and the water drops below this temperature, the element will be activated until the water temperature returns to 60 degrees.


When you turn on the hot water tap, hot water leaves the geyser and is replaced with cold water. This means the water in the geyser is now at a much lower temperature, so the element kicks in to reheat the water to 60 degrees. When you are not using hot water, the geyser temperature should remain the same since no cold water is being added, but this is not the case because even when the geyser is not being used, some of the heat “leaks” through the geyser tank and into the surrounding environment, and this causes the water temperature to gradually decrease. When this goes below 60 degrees, the thermostat activates the element to heat the water up again. 


So, let’s get back to this question of switching the geyser off. The two main arguments for and against switching off the geyser are as follows:

1)      Switching your geyser off will prevent the element coming on to maintain the set temperature during the times it is not being used, and as such you will save energy

2)      If you switch the geyser off, the water inside loses heat and when you eventually turn it on again, it has to heat the water from a much lower temperature to get to the set point, which uses more energy than  coming on periodically to keep it at temperature


The reason there is so much disagreement on this issue is that both arguments are correct to a certain extent. So let’s try to sort fact from fiction:

The extent of heat loss differs from geyser to geyser, and the usage patterns in households differ drastically. We can go into the principles of thermodynamics, and the law of conservation of energy, but the fact is that the potential saving depends completely on your specific geyser and pattern of use. 


There are many documented studies available on the merits of switching off your geyser, some of which have been carried out in labs by scientists, and some by regular people in their own homes. The results of these tests show savings from 2% to 40%.  The obvious problem with these tests is that the playing field is not level, which is essential for good science. Some household have two people only showering in the morning, and some households have two people showering in the morning and two in the evening. Some geysers are newer, or better insulated.  Some of the reported savings are simply a result of a placebo-like effect, i.e. because you are conscious of your hot water use, you use less hot water. Simply reading about somebody’s savings should not be a good enough reason to believe the same would apply to your house.  


The water you use needs to be replaced and get heated up again, so switching your geyser on and off will never reduce this basic amount of energy needed. So, the only time you are wasting energy is during the period where the water has reached its set temperature and starts decreasing slowly due to that heat dissipating into the environment. This is more the case with old geysers, where the insulation is less effective. 

Even if your geyser and piping were perfectly insulated, you could not make any savings at all by switching off because you are only using more energy to heat the water you have emptied out of the geyser.

Three things that affect geyser power consumption are

1.   1. How much hot water you use 2. How often it’s used and 3. The condition of your geyser. 

3.     It’s obvious that there is no universal right or wrong here, since all of these factors can be different in every situation.  So instead of picking a side on these points, I have decided to rather explain how to make real savings, and to make a valid difference with your geyser usage.  I would advise the reader to simply think about how you use hot water:

A. Try to use less water – Shower rather than bath, shower for shorter periods and don’t use hot water for anything other than showering (Definitely not for washing hands!).

B.  Turn the geyser off only when you will be away for longer than 1 day.

C.  Make sure your geyser and pipes are properly insulated.

D.  If you have an old geyser, consider upgrading, or even better, consider a solar water heater OR heat pump


These measures can reduce the electricity consumption of your geyser.


So, in conclusion, the benefits in terms of actual electricity savings achievable by controlling your geyser operating times in order to save yourself some money is inconsequential when compared to the difference that could be made by changing the period of use AND installing a renewable energy solution. The energy required to heat water derived from the sun is free! The residential sector makes up a large part of the electricity demand in South Africa, and the hot water portion of this is significant. 

Please visit one of our websites and request a quote on a Heat Pump or Solar Geyser.. we are saving clients hundreds of Rand’s a month..




12 responses to Switch your geyser on and off ! – Does it save me money or not ?

  1. I want to know whether switching your geyser on and off every evening damages the thermostat or shortens the thermostats life span. Can someone help me here? I have an old geyser since 1988.

    • Hi Carel, Thermostats (and heating elements) are designed to switch on and off by themselves, well actually the thermostat switches the element on and off. The thermostat is the part that determines the water temperature and then turns the element on and off as required. So the thermostat already switches itself on and off. As for damage. like i said, it is designed to do just that, however, logic(well logic in my field anyways) tells me that it will shorten the lifespan, if you let the geyser cool down by 20’C, everyday. The argument is expansion and contraction… When its hot, it is expanded, then(on normal operation) it cools by 1-2’C, the thermostat picks that up, switches on and heats it up by that 1-2’C. Now it takes very little effort to go from 100kph -110kph in the car, same with this. If however you you switch it off for hours on end, the geyser might cool by 20’C, which means that the thermostat contracted a lot more(things shrink when its colder) AND it now has to heat up by 20’C (like going from 80kph to 120kph) it takes a lot more effort.

      So the only real damage that will occur is because of the expanding and contraction of the element and thermostat because of a 1 x 20’C drop instead of the usual 5-10 x 2’C drops…

      I hope this makes sense,

      Kind Regards

  2. Thanks for the “big kettle” to explain the concept of g=turning off and on of geyser, and for knowing the turning off geyser doesn’t necessarily save electricity. But my case seem a bit different. I have a large family and we only use our geyser for bathing purpose. We do use up all the hot water in the morning when preparing for work and school. What I do is to turn off the geyser after using up all the hot water and turn it on again around 4am so that we can have hot water for bathing in the morning? Please advise.

    • Hi Peter

      Thanx for the question…

      It basically ties in directly with what is written in the post, some people will argue that you will save a little money because it takes alot of effort to go from 50-60 than what it does 20-50, The same way a car can go from 0-100 easily but use more fuel from 100-140 and to keep it at 140 will use a lot of energy. Others will argue it depends on the plumbing, type of geyser, usage patterns etc…

      Whatever the argument, It will certainly NOT save you R300 a month on a R1000 bill, it might save R10 or R20 though(every situation is different and there are a lot of variables)

      The only way to save a considerable amount(What I would considder R300 or more on a R1000 bill) in your case is to either use a shower with low flow shower heads or replace the heating source(electric element) with a Heat Pump or a Solar geyser , a gas geyser or even a induction geyser(although the induction type wont give you 30% savings on its own)… even Geyser blankets and pipe insulation will help…

      We are specialist with the Solar and Heat Pumps and can prove their performance with case studies and client experience…

      Gas and Induction heaters are not our field of expertise although some people swear by them..

      Whatever the choice, anything is better that the conventional energy guzzling elements

  3. Geysers installed in the ceiling are subject yo much higher temperatures than environmental temperature (outside), even in winter and more so during summer. The type of roofing material also has a big influence. It gets extremely hot in the ceiling space during summer in houses covered with a Zinc roof and even on a sunny day in winter it gets hot and heat loss from geysers is minimal as result of temperature differences inside and outside. The biggest heat loss will occur during night time.

    • Hi Pieter, you are 100% correct that roof spaces become much hotter. The thing though is, if your geyser is properly insulated, it is designed to keep all the heat in. This then also means it keeps all the heat or cold on the outside, out. The same principle applies to a blanket, it keeps your body heat in and the cold air out. So a well designed system should not be affected to much by the surrounding atmosphere.

  4. Since I started switching off my geyser I have saved HUGELY on electricity consumption bills. And from the research I have done, solar geysers are not the total solution as the solar geyser still works on the same principle with valves, anodes, elements and thermostats so the wear and tear on the geyser is exactly the same as it is on an electric geyser.

    • Hi Michele, a Solar Geyser and a normal geyser are one and the same thing, they all have there required safety valves and things. With a few very important differences though. a Solar Geyser is much better built and a good one will last in excess of 20 years. a Solar geyser’s primary heating source is the sun, so whichever size you get, you should get one free tank a day, where with an electrical geysers you get NO FREE TANKS. a Solar geyser can totally be a complete solution if you have the budget to size it big enough, however due to economical reasons, they do come with a backup heating element and thermostat for days when it’s raining. Sizing and Make are very important.

      Wear and tear should differ tremendously from a normal geyser because we service them bi-annually, No One ever services their geyser. Elements and Thermostats last longer since they are not needed nearly as often as on a normal geyser…..


      You should choose the right system and installer

  5. i understand that solar geysers are sized up according to thesize of the family. can u clarify this for me please: does the flat plate pannels over-flow when its over sized? say a 300L for 2 adults and a 8 year old. some people say it does and others say the bigger the better. so which is which there?

  6. Hi Terrence,

    I also answered most of your questions on the other post (just click on the below link)


    Generally, it depends on how you use it… If the wife prefers a bath full to the brim each day, 300lt might not be enough, but if you are already using your water and electricity sparingly a 300lt should be just fine and won’t really overflow unless its left alone for 3+ days.

  7. Could you please tell me where you got this article from …… because I wrote it 3 years ago and it certainly wasn’t for GESS Green

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