Kettle versus Qooker

Friends, have you ever spent time with someone who has just had a Qooker installed?

Discussing topics even tangentially related to the heating of water will result in a torrent of gushing hot water praise for this life-changing water-heating innovation.

And somewhere in the gushing torrent will typically be claims that a Qooker is more energy efficient than heating water using a kettle. Having carried out extensive studies of the boiling of water in domestic settings, I was sceptical. So I asked the oracle that is OpenAI’s ChatGPT about the pros and cons of using a Qooker and using a kettle.

Click image for a larger version. Chat GPT thinks that a Qooker is more efficient than a kettle.

ChatGPT was of the opinion that using a Qooker was more energy efficient than using a kettle. But then ChatGPT is truth-agnostic:

Click image for a larger version. Chat GPT admits it cannot distinguish between ‘true facts’ and ‘false facts’.

So I thought I would make a calculation, and that is what this article is about. In case you don’t have the time to read the whole article, my conclusion is that there is not generally much difference in energy efficiency terms.

The actual answer depends on how much boiling water you use each day, and how much extra water you leave in the kettle each time you boil it. Yes, it’s that tedious.

I think there are a wide range of use cases where a Qooker might well be more energy efficient than a kettle. However, what Qookers actually save is time, and I think that is why people who own them like them so much.

What is a Qooker?

A Qooker is a device that preheats around 3 litres of water to just over 100 °C and holds it in a pressurised, insulated container – like a vacuum flask – under a kitchen countertop. Other brands of water-heating tap are available.

Click image for a larger version. Illustration of a Qooker with publicity photograph .

When boiling water is required – such as for making tea or coffee, or filling a saucepan – water at around 100 °C can be dispensed immediately via safety-tap.

Energy Efficiency

The energy-saving potential arises from the fact that the tap dispenses just the amount of hot water required. This is in contrast with a kettle which usually requires some amount of extra water be boiled each time boiling water is required.

However, in order to realise this benefit, the Qooker has to keep around 3 litres of water in a pressurised container at around 108 °C – and some of that heat leaks out constantly into the kitchen.

So the question to answer is the relative magnitude of these heat losses (boils extra water versus losing heat 24/7). I decided to write a spreadsheet. Obviously I asked CHatGPT to do this first but the result wasn’t very helpful.

Click image for a larger version. Chat GPT’s suggested spreadsheet  didn’t take account of the fact that kettles and Qookers waste energy in different ways: one by keeping water hot for an extra time, the other by heating extra water.

So I wrote my own spreadsheet. You can download it here and it’s key features are shown in the image below.

Click image for a larger version. It calculates the extra costs of using excess water and compares then with the constant losses from teh Qooker.

My conclusion is that while it is possible to use a conventional kettle more efficiently than a Qooker, in most common circumstances, the Qooker is likely to be more efficient.

For the scenario illustrated above – boiling 10 cups of water for tea/coffee and preparing a one litre saucepan of boiling water – both Qooker and kettle use 0.42 kWh to heat the water, but the Qooker ‘wastes’  0.24 kWh/day keeping the water hot and and the kettle ‘wastes’ 0.35 kWh/day boiling extra water.

Over a year the saving of 0.11 kWh/day would add up to a saving of around 40 kWh/year, around 10 kg CO2/year, and around £14/year. The financial saving on a £1,000 + investment is negligible, and in carbon terms (and financial terms) the money would be much better spent on insulation!

Which raises the question…

Why do people love their Qookers?

People love their Qookers. Their relationships can be almost as profound as their relationship with their Air Fryers. And as far as I can tell, the reason is that aside from their emotional investment in their tap, the Qooker saves time.

Think about the difference between using a computer where opening a file takes many seconds – and the windows are slow to refresh. One learns to live with such computers, but after one has used a faster computer, returning to using the old computer seems painful.

Similarly, I think this sense of instant availability can feel magical after a lifetime of waiting for the kettle to boil. Two minutes per cup of tea; ten minutes per day; an hour a week; two days a year; a big fraction of person’s life could be taken up waiting for the kettle to boil.

People’s devotion is nothing to do with energy saving, and certainly nothing to do with cost savings – which are all offset by the need to regularly replace filters.

So will I be getting one? No. It’s just one more thing I don’t need.


Friends, I ignored lots of things in this article.

  • I ignored the fact that the lost heating energy isn’t really ‘wasted’ for either kettles or Qookers: it all goes into heating the house.
  • I ignored the mass of the kettle which must be re-heated each time the kettle is boiled.
  • And I ignored embodied carbon dioxide.
  • And I ignored safety concerns. 


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8 Responses to “Kettle versus Qooker”

  1. trcal Says:

    Thank you! I was intrigued by this very question. It does scream rebound effect to me though – if people believe it is cheaper and more efficient, but especially with it being quicker and more convenient, I fear there is a tendency to use it more and so, as with so many other areas of our life, our demand for energy creeps up.

  2. protonsforbreakfast Says:

    Good Morning: Good point. I can imagine people might come up with imaginative ways to clean items using instantly available boiling water when boiling a kettle would have been a faff.

    All the best


  3. Greg Says:

    I do not know what the regulations are in the UK but in the US, I would be hesitant to use this as a source hot water for ingestion. As a matter of fact, the last time I replaced a fixture for a sink, the fixture came with a warning to not consume hot water through the fixture as the hot water could leach lead from the solder joints but running cold water into an appliance to heat was acceptable. We do have similar units here with a separate outlet but I suspect they do not use lead in it’s manufacturing.

    • protonsforbreakfast Says:

      Greg, Good evening:

      that is a point I had not considered. Holding boiling water in contact with metals for prolonged periods will dissolve small portions of the metals and leach impurities out of them. But I suspect that this apparatus is made with high quality stainless steel and that the parts are welded together without solder. This is similar to the technology used in catering equipment such as hot water ‘boilers’ and coffee dispensers.

      Historically in the UK, water from the hot water tap did not come direct from the water mains but sat cold in an open tank in the loft before being heated and stored in a – typically copper – cylinder. This was not considered potable.

      Nowadays, the hot water comes directly from the mains and is heated and stored in a stainless steel tank. Such water is – as I understand it – completely potable. So if one uses it for cooking, one save a little bit of energy.

      But thank you for easing that – somehow I just didn’t think about it.


  4. alexbutcher Says:

    So glad you put this together – this experiment had been on my mind since I installed a Qooker for reasons of convenience.

    Something else you didn’t control for though, which could be material: there is also excess boiling liquid produced by the qooker – after you finish filling a saucepan / mug with boiling water there is residual boiling water left in the flexible hose that connects the pressure container to the end of the tap. This water obviously dips below boiling quickly and becomes analogous to the waste water that remains after boiling the kettle

    • protonsforbreakfast Says:

      Alex, Good Morning. And Thank you! That could be very significant! I’ll make an estimate for that and see how it affects things.



    • protonsforbreakfast Says:


      I’ve made an estimate now and it doesn’t look that significant.

      I looked up the design diagrams at and it looks like the pipe connecting the insulated vessel to the tap is something like 6 mm outer diameter stainless steel. This has an internal diameter of around 4 mm and even 1 metre of it has a volume of only 0.013 litres – about 13 ml compared with typically 150 – 300 ml of excess water boiled in a kettle.

      But thanks for alerting me to that!

      All the best: Michael

      • alexbutcher Says:


        My eternal thanks clearing this up for me! The prospect of having to recycle my beloved quooker was causing significant anxiety!



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