Review of Combisave – does it save any water or gas? All is revealed here!

I have been monitoring my new Combisave device over the past month and have now enough data to calculate some initial findings in terms of water, gas and time savings.

Serendipitously, June is a perfect month to monitor gas use for hot water heating, as even with the non-summer we have been having lately, we have not put the heating on at all through the past month, and as I do not cook with gas, the only gas use through the summer months is for hot water use.  Also, luckily, I have monthly readings of summer month gas usage for the last two years (yes, I know, I’m a bit geeky) and so have a high level of certainty about my household’s daily summer gas usage – typically averaging 5.18 kWh per day (as measured over June-Sept 2011).

Also, usefully, I have been on a water meter for years, so  can also easily calculate a daily summertime water usage volume from my previous bills.  Typically, for our two person household it has been around 200 litres a day.

So, how has the Combisave device performed in this past month.  Roll of the drums please…

In the month of June we used a total of 5470 litres of water (this includes 2 short hose pipe uses, after the hose pipe ban was lifted I hasten to add), that works out at around 90 litres per person per day.  Typically, in years past, we have used an average of 100 litres per person per day in the summer months.  So that is a 10% potential saving.  The only other variable in this is the fact that, in years gone past, we might have used the hose pipe more for watering the garden, as the summers have been a little better and drier in recent years!  So it is not totally conclusive.

Turning to the gas saving, which can be more conclusive, I have seen an average daily usage of gas of 4.77 kWh per day in June.  So, we can say that there is probably a small gas saving through the use of the Combisave device of 0.41 kWh per day.

In terms of a time saving, well, it hasn’t saved me any time at all in the mornings whilst waiting for the shower to warm up (if I’m first in), it’s still just over a minute’s wait unfortunately.

To put some monetary savings to these figures:

Water:  If we are, on average, saving 20 litres of water per day,  then total yearly savings could be around 7300 litres.  Now, the average metered price for water in the UK is about 0.25 pence per litre.  So we can calculate that my yearly savings on my water bill could be around the £18 mark.

Gas: If I am saving 0.41 kWh per day on my gas usage for water heating, that will amount to  about 150 kWh of gas saved per year.  Using an average gas price of 4.5 pence per kWh unit, my yearly saving on my gas bill could be around £6 – 7

That gives me a total combined water and gas saving of approximately £25 per year

So, given a total installed price for the Combisave of approx: £130 (made up of the price of the unit plus the plumber’s installation charge – but this will vary), we are looking at an approximate 5 year payback.  Which is reasonable, as the lifetime on the device is said to be 20 years or more.

I’m happy with this, and am glad I invested in the device.  However, what I am not so comfortable with is the extraordinary claims that Combisave have on their website regarding the potential savings that people can make with their gadget.  I feel people would be quite happy with a 5 year payback (or more than likelyless for a bigger household) and then ongoing, year on year, savings on their gas and water usage (if on a meter), there is really no need to ‘over promise’ to such a significant degree, only to really cheese people off when they do not achieve those savings after installation. That isn’t the way to get ‘word of mouth’ recommendations for your product.

So come on Combisave, your product has merit, please don’t spoil it by extraordinary, and, in my opinion and personal experience, overblown claims of monetary savings that it will simply not deliver. 

Related blog post on the subject:


21 comments… add one
  • Dave Furlong July 9, 2012, 9:50 am

    Hi Paula. it's great that you have tested the CombiSave and that you have some possible savings. There are some reasons why your savings arn't as high as the goverment backed indepent test and that is:-
    1) The savings are only a half to a third less in the summer as the incoming mains water is some 10-15 degrees celcius warmer than in January. (so you could double your savings roughly)
    2) The savings figures on our web site are based on a family of 4( so again you could possible double again)
    3) Each CombiSave needs to be tuned to each boiler to get the best savings (Temperature and flow rate adjustments) so you could possible improve on performance.
    4)  combisave is a replacement to preheat so people need to be sure that theirs is turned off (Preheat costs around £150 per year)
    5) And don't forget that CombiSave maintains the outlet temperature of the water all year round,so no more luke warm baths with smaller boilers.
    If I'm ever in the area, can I pop in and see how it is working?
    THanks again
    David Furlong

    • Paula July 9, 2012, 10:41 am

      Hi David

      Thanks for your comments and our chat just now.  It’s really refreshing to see a manufacturing engaging in debates about their products.

      And yep, good point about the savings being seasonal on the water savings, I should have thought about that.  I’ll continue to monitor over the coming months and into winter to see how the water savings change over the seasons. I guess there is an effect on gas too? but I will not be able to monitor that so easily as the space heating will be on over winter months which interfere with my gas readings.

      Good point also about the pre-heat.  I haven’t got that on, and haven’t ever used it as I felt it’s just a waste of energy really, but I’m sure a lot of people do have it switched on (is it a default setting I wonder?)

      And thanks for your offer to come around and check my device. That will be greatly appreciated, especially if you can discover why I’m not saving time with Combisave as I would have thought, logically, that I would have seen a reduction in waiting time for my morning shower.

      Best wishes for now


  • Allan Roberts July 31, 2012, 11:18 am

    Hi Paula, I am delighted to have found your review of the Combisave as I am seriously thinking about having one fitted, to the extent that I was trying to calculate the savings for our situation!
    Both my wife and I are in our 70’s so of course, as we aren’t in the banking fraternity, we have to spend our money as wisely as possible.  We have had a Worcester Highflow combination boiler for 7 years and have always been concerned about how much domestic water we waste when washing up , etc.
    My calculations have only been on the water wastage side, so any gas saving is a bonus.  I measured the ‘unsatisfactory’ water during washing up and have found that it takes 0.5 to 2 washing-up bowl contents before the water is hot enough (this varies because there is a small hot water tank inside the boiler – is this pre-heat?)  The bowl holds 5 ltr so wastage is 2.5 to 10 ltr, which twice a day means 5 to 20 ltr per day.
    We also each have 1 wash or bath or shower each day and presumably the same amount of water is wasted for each operation hence 5 to 20 ltr per day also.
    So we are wasting between 10 and 40 ltr of water each day and as the cost of metered water down here in the South West is about 1p/ltr (4 times the average!) the eventual savings over a year would be between £36.50 and £146.
    That’s the good point – the bad point is that if the internal ‘pre-heat’ tank is shut off the boiler, which floor-mounted in the airing cupboard, cannot be used for airing purposes – heap big problem for wife!
    Also during hot weather, the water wasted at washing up time goes into the water buts, but we haven’t done much of this so far in 2012.
    I would like to see any comments you might have about my reasoning.
    Allan Roberts

    • Paula July 31, 2012, 7:50 pm

      Hi Allan

      Thanks for your comment.  Your reasoning and calculations seems sound.  You might find that your shower  might waste more water than your kitchen tap, as showers can work through about 9/10 litres a minute as compared to around 6 litres for a sink tap.  It’s worth measuring with a bucket to see how much you are wasting.

      David from Combisave points out, in a earlier comment to this blogpost, that you will save more in winter than in summer monhs as the incoming water temperature is much lower in the winter months, so takes longer to warm up.  Hence your savings will be more in winter with a Combisave installed.

      Don’t forget though, if you and your wife shower/bathe directly after one another then you will not waste so much as the water is already warm fro the second shower.

      You sound as if you have the ‘pre heat’ function on your boiler.  That can, according to David from Combisave, cost you quite a lot over the year.  I appreciate switching it off may mean you don’t get the heat in the airing cubaord in the summer months, but is that so much of a problem?  I’ve never had an airing cupboard, although I remember one from my youth in my mum’s house, and so don’t really miss one. Switching the ‘pre-heat’ off might save a you a hell of a lot of money on your gas bill!

      Taking a mid-range view of your potential savings, so maybe £70 per year in water bills, you are probably looking at a between  2 and 3 year payback (depending on your Combisave installation costs of course) with your high water meter costs (my workings were based on 0.3pence), and with a pre-heat gas saving too you could reduce that even more in terms of your gas savings.

      So, given the information you have provided, I would suggested that a Combisave could be a good investment for you.  I will alert David Combisave to your comments and see if he wants to add anything.

      All the best with it, and we’d be interested to hear how you get on if you take the plunge.


  • Robert Cooper October 31, 2012, 1:31 pm

    Hi All, Very interesting blogs, especially as I'm just about to instal a new heating/water system and combi boiler, and additionally picked up a combisave leaflet this morning. I will have to spend some time digesting all the information.
    Robert Cooper. Wem.

  • George Pilkington December 17, 2012, 10:10 am

    Hi everyone, Grear posting Pauls. I have undertaken numerous environmental, improvements to our home. I mentioned at a recent meeting that I was concerned about the amount of wasted water when using a our Greenstar 24iJunior Worcester boiler, as this was one area that I found difficukt to solve.  I was told that a combisave was the gadget I needed. I checked out the web site. I am not on a water meter, ( my partner does use a hell of a lot of water….nad I did not want to save money in one area to be spend on her water usage!!) Then did a search and found a product, that costs less and has the same effect, called combismart. .It’s a simple, thermostatic device that’s easy to fit and for those on a water meter, can save more than £100 a year on bills (or average £25 if not on a water meter).
     I have emailed them to ask for details about the differences from their product to combisave..and will do the same with combisave…
    Combismart costs around £30 plus fitting…….I am having British Gas call around in the NY to give us a quote….for a combisave…….if this works I may now consider a water meter….Cheers George Pilkington

    • David Jones February 26, 2013, 3:51 pm

      Hi, George,

      Any response from Combisave or Combismart or any further thoughts about comparisons between the two products, please?

      • Paula February 27, 2013, 5:08 pm


        I can report that I have talked to CombiSmart and at the moment they are not selling the product as a retail item.  they are only selling it as a package through accredited plumbers who have been trained to install it, and only in certain areas of the country.  So currently it is not possible to compare the two products easily.  I might, at some point in the future, replce y combisave with a combismart to test if there is any difference with the two products, but i’ve no plans to do so in the immediate future.

        Sorry I can’t be of more help

        Best Paula

  • Rodger Harper February 7, 2013, 9:10 am

    Hi Paula, read your comments with interest and in most cases in the UK would be about right and manufactureres do tend to over blow their trumpets a little, Can't really blame them. I guess your findings are based on gas, water charges & water pressure in your area. As we are in the IOM and water pressure aversage is around 5-6bar and our gas prices nearly double. The savings will be considerably more as the flow will be much greater and take longer for the water to reach set temperature therefore burning much more gas, would it not. Kind Regards 

    • Paula February 7, 2013, 3:54 pm

      Hi Rodger

      Thanks for your comment.  I guess, in your circumstances, that the potential savings will be greater.  Especially if your gas prices are twice ours on the mainland (that is quite shocking!  I had no idea they could be so high).  I’m assuming you are on a water meter too?  If so, then you will save a lot more as a result of your water pressure.

      I think it is well worth investigating for yor situation.  just make sure you get a good reliable plumber to do the install for you.

      All the best, and ill be interested in hearing how you get on with it.



  • Tom March 12, 2013, 3:31 pm

    Hello All,

    I thought I should post some more information here about CombiSmart.

    Firstly, the current website addresses the Housing Association audience. We’ll be launching our new site at  which will give details of where we’ll be selling to the trade – so David and George, you’ll be able to purchase yours soon. Watch this space we’ll write a post when we launch.

    CombiSmart boasts some great features of which we are particularly proud:

    CombiSmart is an inline device with a straightforward design with no kinks or bends – meaning it allows for hassle-free installation without the need to adjust existing pipework. CombiSmart can be fitted in less than 15 minutes. The bypass screw is prominent so easily accessible to calibrate to your boiler, once the device is fitted. Finally, CombiSmart is a small, discreet device delivering big savings. The product was independently tested by Enertek International, a consultancy based in Hull that tests for most of the major boiler manufacturers. You can see the expected savings for CombiSmart at . In brief, CombiSmart is expected to save around £30 in gas and £80 in water every year. Importantly, every home is different and everyone’s habits vary, hence we published our workings to allow the discerning home owner to work out what they themselves will save.


    Figures based on turning on a hot water appliance 24 times within a 24 hour period with the boiler at cold, 6 months (180 days) during a year. Test results as per a 30 cdi – Worcester Bosch boiler. Gas prices based on £0.0449 per kWh (Energy Saving Trust 2012) and an average £0.0025 per litre supplied and taken away (OFWAT February 2011/12). Please note water prices will vary by Water Company. KgCO2 figures from EST 0.183KgCO2/kWh and Water UK 0.79gCO2/litre.



    • James December 28, 2013, 9:40 pm

      Why do the CombiSave instructions say 'For best results the ComiSave should be fitted within 500mm of the boiler outlet'?

      If there is a long pipe before the tap, this will allow full flow several seconds before hot water is available from the tap. Wouldn't it be more sensible to fit the CombiSave as far as possible from the boiler?

  • rob March 24, 2013, 11:02 am

    Hi there,

    I am wondering if like me you live in a home two adults three children and have say bathroom and en-suite bathroom on 1st floor. Then kitchen, utility and wc on ground floor all having basins or sinks. Now with a combisave valve fitted and hot water was being drawn off let say one shower, filling a bath and one of the hot taps on ground floor are you likely to get an acceptable flow of water from all of these and how long could you be waiting for this? I have a worcester 350 wall hung boiler that i had installed approx 12yrs ago so i realise there are better boilers out there but to replace a good working boiler is obviously not a cost effective option!

  • peter October 13, 2013, 5:32 pm

    Turning on the hot water for a bath or sink should not be counted as the initial cold water is used to get the temperature right.  Is this included in the 24 uses per day?  And a 5m pipe run has 1 litre of water in it.

  • David Smith October 29, 2013, 3:41 pm

    I have a much cheaper alternative to this device. In fact it is so cheap and equally as good that it is free. The Combismart, as I understand it, slows the rate of water flow until such times as the temperature of the water builds up to an acceptable level. It is just a device that contains a thermostat which controls a valve.

    The device I have is called a 'hand' and this useful thing opens the tap on the sink and shower until it feels that the water is at an acceptable temperature. At this point it opens the tap fully.

    I have used this personal device for over 70 years and it  still works

  • Tom Bates March 2, 2014, 9:40 am

    Interesting comment David!

    Do the Combismart and Combisave restrict the water any more effectively than manually regulating the flow with the tap handle? I assumed that they did, somehow 'fooling' the boiler into thinking that the hot tap / shower is more open than it actually is – something that couldn't be replicated by fiddling with the tap.



  • Ant Morgan February 24, 2016, 7:28 pm

    My combisave valve seemed to play up, screeching at times and I guess the calve not opening up enough as I can run gallons of water with no hot water, please help

  • John D July 5, 2016, 8:52 am

    Does your combisave affect the water flow rate when up to temperature? We have a combismart device fitted which we are considering having removed because the flow rate from the tap is reduced even when the water is up to temperature. Not by a lot but enough that you really notice it in the shower (we have a thermostatic mixer shower running directly off the boiler). Wondering if Combisave suffers from this same issue or whether it might be a good alternative.

  • George Hildreth May 22, 2017, 1:48 pm

    We have just moved over to a water meter but haven’t had a bill yet. But it does change your habits on water consumption. When running water for dishes I fail the watering can until the hot comes on. I am going to get a water collector for the garden. We flush the toilet only after a no 2

  • Clive Butler April 21, 2018, 2:49 pm

    Wow. I think after reading all that I might settle for a large funnel, a piece of pipe and a water butt! Very impressive amount of research though!
    Thanks, Linda.


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