Instant boiling hot water taps...transparent costs for the first time

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Headlines

This article is about the type of instant hot water tap that permanently holds a tank of water close to boiling point to provide instant boiling water in the kitchen.

It does not cover the costs of variants of these products that have other features such as chilling water (which will almost certainly add to purchase costs).

It gives a clear comparison of the annual energy costs of using an instant boiling water tap compared to using a kettle that isn't significantly overfilled.

It is a common perception that instant hot water taps are a cheaper to run than a regular kettle for boiling water.

Based on my analysis and assumptions, the headline results for the most energy efficient instant boiling tap I can find are:

• If you drink 23 mugs of tea or coffee a day (around 6.5 litres of boiling water) the annual cost will be SIMILAR to the kettle

• If you drink LESS than 23 mugs a day, it will cost you MORE overall to use an instant hot water tap

• If you drink MORE than 23 mugs a day the instant boiling water tap starts to save you money, though only a very small amount.

23 mugs of tea or coffee a day works out at around 7.5 litres of boiling water. In old money, that's a whopping 13 pints of boiling water every day. A survey of 412 homes by the Energy Savings Trust found that the average UK homes boils enough water for around 8 mugs of tea or coffee a day.

For other instant tap brands I've analysed, you need to drink a LOT more than 23 mugs per day for them to work out cheaper than a kettle.

Instant boiling water taps do of course provide 'instant' boiling water. Boling enough water for two mugs of tea in my own kettle takes 90 seconds. The kettle isn't as convenient, but I believe they are a lot cheaper overall in most normal household situations.

I've included a tips sections on both buying instant hot water taps, and tips on energy saving when boiling water with whichever type of product you use.

The costs below do not take into account the purchase price of instant boiling water taps. These vary greatly and are generally several hundred of pounds.

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Cost of energy comparisons

The tables below show the annual running costs for three different quantities of mugs of tea or coffee drunk each day:

• 10 mugs of hot drinks per day (slightly more than the national average)

• 20 per day

• 30 per day

Of course, water is boiled in homes for other purposes than making hot drinks, such as for cooking. For that reason the total volume of water heated is also given in these comparisons.

The total yearly energy costs are shown in the red boxes.

The comparison is between an ordinary jug kettle and four brands of instant boiling water tap based on manufacturers own technical information.

The numbers in each row in the tables below are:

Row A - the cost of the energy used by instant boiling water taps to keep the water hot and "ready and available" throughout the year. This varies for different manufacturers, and it is known in the industry as the "standing losses".

Row B - the cost of reheating incoming cold water to replace the boiling water that has been dispensed.

Row C - the total annual costs (rows A and B added together).

Row D - the average cost per litre of boiling water for each situation.

One assumption in these numbers is that ordinary kettle users overfill their kettles by an average of 20%. Achieving this is quite realistic if you are cost and energy conscious and use the tips below. Overfilling kettles is quite energy wasteful and adds up in the long term. This is something that quite rightly features from time to time in energy efficiency campaigns.

Other more detailed assumptions are shown at the end of this article.

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As you can see in the above case, the kettle costs are cheaper in all cases.

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In this example, if you use an average of 20 mugs of tea per day then the costs for the ordinary kettle are very similar to the Quooker. The other brands are still much more costly.

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In this case with a higher consumption of 30 mugs of tea a day on average the Quooker becomes slightly cheaper over the year, saving around £5 a year. But 30 mugs of tea is around 2 gallons of boiling water per day, a bucket full of boiling water...every day!

Even when boiling this much water, the other instant tap brands are still more costly to run than a kettle.

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Conclusions...so far

As you saw above the Quooker works out similar to the kettle when you reach 23 mugs of use.

For the other brands to have equivalent costs to a kettle you need to drink the following amounts:

Qettle: 60 mugs/day (19.5 litres/day)

Fohen: 49 mugs/day (15.9 litres/day)

Hyco: 29 mugs/day (9.4 litres/day)

As mentioned earlier the comparisons all assume that if you are a kettle user then you only overfill by 20%. If you pay less attention when filling your kettle and typically overfill by as much as 50% then if you drink 11 or fewer mugs a day then a kettle is still cheaper than the most efficient instant tap I assessed, the Quooker.

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Other instant hot water tap costs and factors to consider

Investment and replacement costs

Given that these products cost several hundred pounds, some over £1000, these products are a significant investment. Additionally, they will need replacing at some point and so replacement costs need to be considered too. I have not included investment or replacement costs in the above figures.

In contrast, kettles are very inexpensive to replace and will last 4-5 years or potentially much longer.

Carbon footprint of the products

But what about the carbon footprint? An instant hot water tap might last 20 years. The official average life of kettles is 4.4 years (though mainstream brands state their designs should last 7).

There are studies that calculate the carbon footprint of kettle manufacture but I can find nothing that allows a comparison with the carbon footprint of manufacturing instant hot water taps.

One simple way to answer this is to look at the material weight of each type of product. An empty kettle weighs a little over a kg. Instant tap units weigh many times that figure, usually in the 8-10kg range, somme more.

A simple conclusion is that, based on the materials content used, the carbon footprint of the instant tap might be 7-8 times that of a kettle.

This is without any additional carbon involved in maintenance of an instant hot water tap.

Maintenance costs

Some of the manufacturers of instant hot water taps recommend replacing items such as filters every 6 to 12 months, and these can be costly. This very recent Which article gives a lot of information about this brand by brand.

If you live in hard water areas then descaling of instant boiling water systems needs to be done periodically for some manufacturers, or filters need to be changed. In the case of Quooker for example the kit for doing this is around £50 and my understanding of the cost for a Quooker engineer to do this is around £150.

Descaling a kettle in comparison costs around 60 pence.

Space

One other factor to consider in making a decision for products like this is that although instant boiling water taps do not take up space on kitchen worktops, they do take up space in kitchen base units

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Tips on buying instant boiling water taps

Size and effect on cost

Boiling water taps are available with a range of hot water tank volumes. The larger the volume, the more hot water you can dispense before waiting for the unit to warm up again. BUT, the larger tank versions are typically more costly to run as they lose more heat sitting there permanently hot in your cupboard.

Additional costs of other variations on these taps

Many manufacturers offer products that offer other features such as chilled water, sparkling water, water filtration and lower temperature instant water for use in sink washing. In my opinion, the standby energy costs of these in kWh are likely to be higher for these more complex products than for a product that JUST provides boiling water.

Using an instant hot water tap of any sort for sink washing is generally the most expensive way to heat water for a sink. See my other article on sink washing costs for the figures.

Other types of products that call themselves "hot water tap"

Counter top units - these sit on the worktop as freestanding units. Some of these hold a tank of permanently hot water similar to the under-counter products above. I would expect the running costs to be similar to under counter units in the cost comparison tables above.

Cold water tank counter-top units - these units have a tank of water that sits at room temperature. Water is only heated on demand. You can tell which ones these are as the water tank is usually very visible. This is usually a simple clear sided plastic tank at the back or side of the unit. I would expect the water flow rate on these products to be slow compared to the types discussed in this article. I would though expect the running costs of this type of hot water will be broadly similar to a kettle.

Hot water taps for dishwashing - these hot water taps are dedicated to heating and dispensing hot water on demand for use in sink dishwashing, but at a temperature A LOT LOWER than boiling. They do not have standing losses (as far as I am aware). As mentioned above, direct use of electricity to heat water is usually the most expensive way to heat water for sink washing.

Getting and calculating the hard £ numbers you need for yourself

In my research I found manufacturers of instant boiling water taps do NOT give enough information publicly to enable you to do the above calculations and comparisons.

This was the reason I researched and wrote this article. The facts on this for the first time.

From the research and analysis I undertook for this article (Autumn 2022), the information the manufacturers showed in their marketing material was consistently and significantly incorrect or misleading in my opinion. These inaccuracies are the subject of a separate blog post on this site and a complaint to the Advertising Standards Agency that was upheld.

If you ARE seriously interested in understanding the energy costs of an instant boiling water tap, ask the manufacturer/seller for the "annual standing or standby losses kWh" figure. Accept nothing less.

In my communications with manufacturers, some initially told me the energy used by the control electronics (a very low figure), and NOT the standing losses figure. An annual standing losses kWh figure will be at the very MINIMUM 80kWh.

If you multiply the standing losses kWh figure by your tariff you will be able to understand the equivalent figure to row A above in the tables.

So, as an example, if the standing losses kWh figure for a product is 100kWh, if you multiply that by 24.5p (the standard variable energy rate from October 2024) you get £24.50. This will be the annual cost you are committed to even before you start dispensing water from it.

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Tips on how to reduce energy using an instant hot water tap

If you are going on holiday turn your instant hot water tap off. There will be an easily accessible switch under the counter next to them. This will be particularly worthwhile for some of the products that are very energy hungry.

Better still, use one of these smart energy monitoring plugs. Then you can turn your system on and off remotely as well at the same time as getting an idea on how much energy it uses on numerous phone apps. These plugs are awesome gadgets; incredibly easy to set up and they use very little energy themselves.

If you use your instant boiling water tap to fill a sink with hot water for washing up it will generally work out around three times more expensive than using your regular hot water if it is heated by gas (and probably more expensive than water heated by oil or propane gas).

Tips on how to reduce energy using a kettle

When using a kettle, there are two simple methods for avoiding overfilling them.

• The first is to fill your mugs with tap water and pour the contents into the empty kettle.

• The second is to mark your kettle like in the picture below to match the mug or cup sizes you actually use regularly. In my experience the "mug" symbols you see in the photo below are based on industry assumptions about the sizes of mug or cup you use.

Some people use a kettle to heat water before then adding it to a saucepan for boiling/cooking. This is the least efficient method as you'll have a) heated the kettle up, and then b) need to also heat the pan up. The most efficient way is just to boil water in the pan straight from the tap. The downside is that unless you use an induction hob, the "cold water in the pan" method will be slower than a kettle.

Eco kettles

There are an increasing number of kettles on the market called "eco" kettles. The energy saving features of these are:

• Some of these allow you to precisely set the water temperature the water boils to. 80C for example. I've not studies these products in detail, but if they have been designed professionally they should also make it easier to fill with the exact amount of water you need.

• They often have insulated sides which will improve the efficiency when boiling but will also keep any residual water warm for several hours.

• Some eco kettles such as this one boast having vacuum flask sides, similar to Thermos flasks. These will be the most effective at keeping heat in if there is any residual hot water left after use. Insulated sides give the kettle a head start when boiling water later and will reduce overall running costs.

From the limited research I have done eco kettles cost in the £80-100 range, so it will take several years for such an investment to payback compared to a lower priced kettle.

From a resource and energy efficiency perspective, these kettles make a lot of sense and make it easier to save energy than using an ordinary kettle. This Manchester University analysis concluded that these sorts of kettles might reduce energy use by around 30%.

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The geeky assumptions

• That kettle users overfill by an average of 20%

• Kettle efficiency of 87% (as measured on two different kettles with 1 litre of water and a start temperature of 17C). I know of other people who have measured this on their own kettles with near identical figures. This also aligns directly with studies referenced here that state kettle efficiencies are between 85 and 90%

• 17C start temperature and 98C boil temperature has been assumed for all calculations on instant hot water tap products above with the exception of the Quooker

• The Quooker actually heats and stores the water under pressure at 108C which adds a little cost. The Quooker then cools the water back down to 100C during dispensing by aerating the flow of water. This is wastes energy, and also explains why Quooker taps are known to be very steamy when being used

• 99% efficiency is assumed for the other instant hot water taps (assuming 1% of dispensed water is left remaining in the delivery hose to cool)

• 24.5p/kWh electricity unit cost. This is the typical Ofgem energy cost price cap from October 1st 2024.

• Standing losses figures were provided to me directly by the respective manufacturers in October 2022. As of October 2024 the best of the products, the Quooker is unchanged.

• Product tank sizes assumed: Quooker 3 litres, Qettle 4 litres, Fohen 2.4 litres, Hyco 3 litres

• Mug size assumed is 325ml

• I have assumed that during 6 months of the year, the heat loss from the instant hot water tap results in a small reduction in the heating costs of the home. I've assumed a gas boiler, efficiency of 88% and with a ratio of electricity/gas unit cost ratio of 3.92 (representative as of Nov 2024)

  
  

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Mark Thompson

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