Small Kettles to save energy

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Please be extra wary with boiling water in a mug the microwave. It's very hard to judge how long it needs and can lead to some nasty scalding accidents if you are not careful.

daveyjp

I would not recommend using a microwave to heat water to boiling point in a mug due to the potential for superheating.

This causes the boiling water to 'explode' out of the cup.

Gerry1

Probably not much in it, but as even a powerful 1000W microwave would take three times as long as a 3kW kettle it's not really an attractive option.

Effician

In a morning when the water in the flask is not quite hot enough ,a 40 sec blast in the microwave is a convenient way of adding extra heat to a mugful of coffee.

kah22

Reed_Richards said:

It is easy to overfill a large kettle and boil more water than you need so it having a small kettle stops you doing that you will save energy.  A typical kettle consumes 3000 W so to keep one boiling for an hour would cost you about 65p.  So you would need to save around 30 hours of kettle boiling to cover the £20 cost of a small kettle.  If your small kettle saved you half a minute of large kettle boiling time than it would pay for itself after 3600 boils, so in about a 10 years if you only used it once a day.

These are very rough estimates.  If you can manage to boil exactly the amount of water you need in your large kettle then the small kettle would offer no savings at all.    

Some calculations in there, but that’s what I’d call an answer

Grizzlebeard

Here is a link to a previous thread relevant to your question.
https://forums.moneysavingexpert.com/discussion/comment/78652037#Comment_78652037
Worth reading the whole thread and not just my comment.

I'm going to slightly disagree with comments that say big or small the energy use is the same and suggest small is better.

Here is the logic, backed up by observations from some loosely based experiments with plastic, stainless steel and aluminum kettles.

When you heat a cupful of water you are also heating the thermal mass of the container it's in - (and heat is also being radiated, conducted and convected into the air around so quicker is better here - but less important than the weight.)

If the "kettle" had zero thermal mass you only need energy to heat the water alone.
If the kettle has the same thermal mass as the water half the energy heats the water and half the energy heats the kettle - using twice the total amount of energy.
By way of illustration, if the kettle had nine times the thermal mass of the water then only 10% of the energy used would be going into the water and 90% into the "kettle".
QED: a smaller (thermal mass) is the more efficient.

Heat retrieval for the next cuppa is a different question but it will never be an 100% efficient process in practice anyway.

Other things being equal, my plastic kettle (lower thermal mass) boils quicker than my stainless steel (higher thermal mass) kettle but I currently use a 1 pint aluminum camping kettle on the gas stove.

This "not heating the container" equation is what makes microwaves much more efficient than conventional ovens which need to heat up many kilograms of steel, glass and ceramics to cook a few hundred grams of food.

BUFF

Grizzlebeard said:

If the "kettle" had zero thermal mass you only need energy to heat the water alone.
If the kettle has the same thermal mass as the water half the energy heats the water and half the energy heats the kettle - using twice the total amount of energy.
By way of illustration, if the kettle had nine times the thermal mass of the water then only 10% of the energy used would be going into the water and 90% into the "kettle".
QED: a smaller (thermal mass) is the more efficient.

Heat retrieval for the next cuppa is a different question but it will never be an 100% efficient process in practice anyway.

Other things being equal, my plastic kettle (lower thermal mass) boils quicker than my stainless steel (higher thermal mass) kettle but I currently use a 1 pint aluminum camping kettle on the gas stove.

Even then though as long as the kettle is not full you aren't heating all the thermal mass evenly. That kettle body in direct contact with the heated water is likely to be heated higher than that outwith contact with the water which will be heated via conduction through the body - plastic conducts heat less well than metal so a bit of a win on the materials front there for a plastic bodied kettle.

Personally, I have a kettle which (afaik) has no minimum amount (other than amount being zero - it is a plate type base rather than an exposed coil) & I measure out 300ml of water in a measuring jug when I want to make a cup of coffee/tea before pouring into kettle ...

Rivers_mum

Bought a small kettle, went back to the normal one, took ages to boil, waste of space. 

jimjames

kah22 said:

I live alone and one possible energy saving idea I was thinking of is buying one of those little one litre type kettles you’d find in an hotel room. Would that be a money saving buy? I see them advertised on Amazon for about £20 - give or take.  Of course I’d still have my standard kettle if I needed more water.  There is quite a footfall through my door!

Well by buying this new kettle you'd be at least £20 worse off because you now have the new kettle and old one! So that will pay for quite a few cups of tea! Although you say you live alone you also say there is a quite a footfall through the door suggesting you need to boil more than 1 cup at a time. You can save energy/money by boiling less water but boiling the same amount of water will cost the same in a big or small kettle. Boiling in a pan on a gas hob may cost you less.

wild666

kah22 said:

Does this sound sensible? My electricity is raising by 21 percent in January so needless to say I’m thinking of ways to save energy.  

I live alone and one possible energy saving idea I was thinking of is buying one of those little one litre type kettles you’d find in an hotel room. Would that be a money saving buy? I see them advertised on Amazon for about £20 - give or take.  Of course I’d still have my standard kettle if I needed more water.  There is quite a footfall through my door!

Kevin

Saving energy means turning appliances off at the wall socket, a smaller kettle might not take as long to boil but if you filled a 1.7 litre and 1 litre kettle to the same mark it is possible that they will use the same number of Watts to boil each kettle. 
Turning appliances off at the wall sockets is the only real way to save energy as with the switch in the off position they shouldn't use any energy. That's appliances like PC/Laptop, printers, external HDD, surround sound speakers, stereo, TV, DVD player, games consoles, smart speakers, smart bulbs/lights, kettle, cooker, microwave, washer, dishwasher, shower. All these draw power left in standby. In my case these appliances use 16 kWh per month in standby mode dropping my weekly kWh usage from 40 to 44 kWh down to just 25 kWh, that's 19 kWh per week.

Reduce the temperature on the thermostat to between 18 and 20 degrees, try 20 degrees then when comfy with that drop it another 1 degrees, then do the same lower to 18 degrees. That really should be the lowest but you could try lowering again to 17 degrees but you might start to feel the cold at 17 degrees.