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.

Notes

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.