To boil or not to boil, a kettle cost and running cost question.

GValue

How much does it cost to heat water in a domestic kettle?

The estimated cost according to the Hugo blog https://hugoenergyapp.co.uk/cost-to-boil-a-kettle/  kettles can boil around 1.7 litres of water in about four minutes. You can expect to pay 6.8p to boil a full kettle. (18 Jan 2023 electric Kwh pricing)

In the past, the cost of heating water in a kettle was mainly dependent upon six factors: 

1. The cost of your kettle and its life.

2. The start temperature of your water.

3. How much water you boil.

4. The efficiency of your kettle

5. How often you boiled the kettle

6. The cost of your energy per kWh.

Now you can purchase a kettle that will allow you to also heat water, without boiling it to say 50c, 70c, 90c as well as a rolling boil. 

So how much can you save by only heating the water you will use, to a temperature you want?

grumbler

GValue said:

How much does it cost to heat water in a domestic kettle?

The estimated cost according to the Hugo blog https://hugoenergyapp.co.uk/cost-to-boil-a-kettle/  kettles can boil around 1.7 litres of water in about four minutes. You can expect to pay 6.8p to boil a full kettle. (18 Jan 2023 electric Kwh pricing)

In the past, the cost of heating water in a kettle was mainly dependent upon six factors: 

1. The cost of your kettle and its life.

2. The start temperature of your water.

3. How much water you boil.

4. The efficiency of your kettle

5. How often you boiled the kettle

6. The cost of your energy per kWh.

I hardly ever boil a full kettle. Usually it's 1-2 caps.

What does this have to do with past/present? It's all the same now, only (1) became less significant.

So how much can you save by only heating the water you will use, to a temperature you want?

By heating water from 20C to 60C instead of boiling it you save 1 - (60-20)/(100-20) = 0.5 = 50%

As simple as that.

That said, all these kettles heating water to the set temperature are more expensive and less reliable, bringing (1) back in force.

GDB2222

When you boil the kettle, it always bubbles away for a few seconds converting water into steam. That’s really completely wasted heat, and the extra humidity may be bad for your kitchen. A temperature controlled kettle that shuts off at say 70C won’t create that steam.

Another reason for using a temperature controlled kettle is that it is quicker. It may only be a minute or two each time I  make a hot drink, but I think it saves me about two hours a month. If I value my time at say £10 an hour, that really rapidly pays for the extra cost of the kettle. 

Le_Kirk

You cannot brew a decent tasting cup of tea with water at less than 100 degrees C, in my opinion!

outtatune

Le_Kirk said:

You cannot brew a decent tasting cup of tea with water at less than 100 degrees C, in my opinion!

Well, you can't brew a decent tasting cup of tea with water at 100 degrees or more either, since that wouldn't be a liquid!

About 95 degrees is the ideal temperature.

Tea made with water at 70 degrees would really be just flavoured hot-ish water.

RG2015

GDB2222 said:

When you boil the kettle, it always bubbles away for a few seconds converting water into steam. That’s really completely wasted heat, and the extra humidity may be bad for your kitchen. A temperature controlled kettle that shuts off at say 70C won’t create that steam.

Another reason for using a temperature controlled kettle is that it is quicker. It may only be a minute or two each time I  make a hot drink, but I think it saves me about two hours a month. If I value my time at say £10 an hour, that really rapidly pays for the extra cost of the kettle. 

I just have a standard kettle.

Making instant coffee with water that hasn't boiled is fine as this improves the flavour compared with using boiling water. I just stop it when I see the first bubble/

Tea however is another kettle of fish ( ).

The water needs to be boiling but is it boiling before the steam starts forming? I guess I could try making the tea with water that has just started bubbling and see what is tastes like.

But it would be good to know how to know the precise moment that it reaches boiling point.

grumbler

RG2015 said:

GDB2222 said:

When you boil the kettle, it always bubbles away for a few seconds converting water into steam. That’s really completely wasted heat, and the extra humidity may be bad for your kitchen. A temperature controlled kettle that shuts off at say 70C won’t create that steam.

Another reason for using a temperature controlled kettle is that it is quicker. It may only be a minute or two each time I  make a hot drink, but I think it saves me about two hours a month. If I value my time at say £10 an hour, that really rapidly pays for the extra cost of the kettle. 

But it would be good to know how to know the precise moment that it reaches boiling point.

The first bubble is this moment. However, it means that  water reached this point locally. Until it starts boiling intensively it's not mixed well enough for the temperature to be the same in the entire volume.

RG2015

grumbler said:

RG2015 said:

GDB2222 said:

When you boil the kettle, it always bubbles away for a few seconds converting water into steam. That’s really completely wasted heat, and the extra humidity may be bad for your kitchen. A temperature controlled kettle that shuts off at say 70C won’t create that steam.

Another reason for using a temperature controlled kettle is that it is quicker. It may only be a minute or two each time I  make a hot drink, but I think it saves me about two hours a month. If I value my time at say £10 an hour, that really rapidly pays for the extra cost of the kettle. 

But it would be good to know how to know the precise moment that it reaches boiling point.

The first bubble is this moment. However, it means that  water reached this point locally. Until it starts boiling intensively it's not mixed well enough for the temperature to be the same in the entire volume.

Yes, but at what point is it ready for the tea without steaming up the kitchen and trashing my kWh £££sss?

grumbler

RG2015 said:

grumbler said:

RG2015 said:

GDB2222 said:

When you boil the kettle, it always bubbles away for a few seconds converting water into steam. That’s really completely wasted heat, and the extra humidity may be bad for your kitchen. A temperature controlled kettle that shuts off at say 70C won’t create that steam.

Another reason for using a temperature controlled kettle is that it is quicker. It may only be a minute or two each time I  make a hot drink, but I think it saves me about two hours a month. If I value my time at say £10 an hour, that really rapidly pays for the extra cost of the kettle. 

But it would be good to know how to know the precise moment that it reaches boiling point.

The first bubble is this moment. However, it means that  water reached this point locally. Until it starts boiling intensively it's not mixed well enough for the temperature to be the same in the entire volume.

Yes, but at what point is it ready for the tea without steaming up the kitchen and trashing my kWh £££sss?

This is a rhetoric question. Some people say 90-98C. And water doesn't always boil at exactly 100C - this depends on the atmospheric pressure.

MikeyPGT

I boil the kettle once a day and fill a flask which lasts for the rest of the day and is sufficiently hot for cups of coffee throughout the day.  I find that this works out cheaper than boiling 6 - 8 seperate cupfulls.

elsien

RG2015 said:

grumbler said:

RG2015 said:

GDB2222 said:

When you boil the kettle, it always bubbles away for a few seconds converting water into steam. That’s really completely wasted heat, and the extra humidity may be bad for your kitchen. A temperature controlled kettle that shuts off at say 70C won’t create that steam.

Another reason for using a temperature controlled kettle is that it is quicker. It may only be a minute or two each time I  make a hot drink, but I think it saves me about two hours a month. If I value my time at say £10 an hour, that really rapidly pays for the extra cost of the kettle. 

But it would be good to know how to know the precise moment that it reaches boiling point.

The first bubble is this moment. However, it means that  water reached this point locally. Until it starts boiling intensively it's not mixed well enough for the temperature to be the same in the entire volume.

Yes, but at what point is it ready for the tea without steaming up the kitchen and trashing my kWh £££sss?

I find that my kettle switches off before any steaming up of the kitchen occurs. 

There are some savings that are worth thinking about. As I only boil the minimum at a time, rarely a full kettle, for me this is not one of them.