Re-boil the kettle - or use a flask? 25 August 2022 at 7:48AM edited 25 August 2022 at 8:38AM in Energy 38 replies 13.2K views

TheGardener

My Mum has 4 cups of tea between getting up at about 7am and her lunch at 1pm. Our question is which is the more energy efficient: should she fill and boil the kettle with enough water to make 4 cups of tea and put it in a flask or should she just boil enough for 1 cup of tea, 4 times

Mum's kettle says 1.4 to 1.8kw on the base and her cup holds 200ml - the kettle capacity is 1.5L

Martin_the_Unjust

Freshly boiled water for tea making every time for the taste.

Water in the flask for economy.

SAC2334

I m just experimenting myself

.If it's going to cost 75 p to £1 next year for each 1000 watts used I  may as well use the least amount of energy for my 4/5 cups a day 

 .Making sure to measure an exact amount of water for just one cup and using a kettle which has a flat bottom with no element to cover,it takes exactly 40 seconds to boil the water for my cup.

I will now measure 4 cups to see if it takes 4x40 secs  =2 mins..

Personally I m not going to get involved in filling a flask because it will lose heat over the day .

Making sure just to boil only a cup of water is  more important because I ve been overfilling a lot prior to me measuring an exact amount .
I just need to practice now in filling the kettle via the tap for exactly one cup.

I ve probably been guilty of boiling 2 cups of water  wasting energy all my life .

frugalmacdugal

SAC2334 said:

I m just experimenting myself

I will now measure 4 cups to see if it takes 4x40 secs  =2 mins..

Hi,

that should be, 160 secs, 2 min 40 secs.

Alnat1

Maths isn't my greatest skill but to make it simple, say electricity is 60p/kWh and a kettle uses 3kWh.

To boil enough water for a cuppa takes 1 minute (probably less in reality but I'm making the maths simple) so it costs 3p.I do hope my maths is right lol

Is a decent cuppa worth 3p?

2pints

SAC2334 said:

I m just experimenting myself

.If it's going to cost 75 p to £1 next year for each 1000 watts used I  may as well use the least amount of energy for my 4/5 cups a day 

 .Making sure to measure an exact amount of water for just one cup and using a kettle which has a flat bottom with no element to cover,it takes exactly 40 seconds to boil the water for my cup.

I will now measure 4 cups to see if it takes 4x40 secs  =2 mins..

Personally I m not going to get involved in filling a flask because it will lose heat over the day .

Making sure just to boil only a cup of water is  more important because I ve been overfilling a lot prior to me measuring an exact amount .
I just need to practice now in filling the kettle via the tap for exactly one cup.

I ve probably been guilty of boiling 2 cups of water  wasting energy all my life .

Or just fill a cup with water and pour it into the kettle.

TheGardener

Alnat1 said:

...
Is a decent cuppa worth 3p?

Me and Mum both agree taste is always better with freshly boiled water - but after price rises, the priority will be cost over taste. Her plan is to boil enough for 4 cups first thing in the morning and then boil enough for another 4 cups for the afternoon/evening and use a flask. I struggle with the maths of it. 

QrizB

It's obviously your choice, but there are probably other ways to save 10p a day without ruining the taste of your tea.

If your kettle will boil a single mug of water, the difference in cost between boiling it once (with four mugs worth of water) and boiling it four times (with one mug of water each time) will be tiny.

For info, last year when electricity was 20p/kWh it cost 1.22p to boil enough water for two mugs of tea or coffee:

https://forums.moneysavingexpert.com/discussion/comment/78640115/#Comment_78640115

Even with electricity at 60p/kWh that only becomes 3.66p per boil.

TheGardener

Ok so I'm getting the idea the difference will be so small its hardly worth the effort to use a flask - but even if the saving is tiny - does that not add up over 365 days? 
So this is really about habit change when filling the kettle and making sure it is only boiling exactly what's needed each time?

People often post on here that turning the TV off will save next to nothing - but over 365 days and multiplied by the number of TV's in the house - there must be a small saving, no?

MattMattMattUK

TheGardener said:

Ok so I'm getting the idea the difference will be so small its hardly worth the effort to use a flask - but even if the saving is tiny - does that not add up over 365 days? 
So this is really about habit change when filling the kettle and making sure it is only boiling exactly what's needed each time?

My quick calculation seems to indicate that she might save around £1-3 per year based on boiling 1.32 litres twice a day, rather than 330ml eight times a day, accounting for the the additional cost of heating the thermal mass of the kettle the extra times (using a 65p per kWh cost).

The saving from only boiling 330ml of water at a time, rather than 660ml each time would save around £40-60 per year.

TheGardener said:

People often post on here that turning the TV off will save next to nothing - but over 365 days and multiplied by the number of TV's in the house - there must be a small saving, no?

It depends what you mean by off, most modern TVs, anything sold in the last decade uses less than 0.5w whilst in standby, many are now less than 0.25w. Based on the 0.5w limit that means a saving of around 4.4kWh per year, or £2.86 per year based on £0.65 per kWh, so not worth the hassle and certainly not worth the potential to shorten the TV's lifespan. If you mean off as in displaying a picture to standby then yes that is worth doing, if someone left a TV on in the background for an hour a day then turning it off (onto standby) would save them around £35 pa with a modern TV, more for an older TV and considerably more if it is an old plasma TV.

SAC2334

frugalmacdugal said:

SAC2334 said:

I m just experimenting myself

I will now measure 4 cups to see if it takes 4x40 secs  =2 mins..

Hi,

that should be, 160 secs, 2 min 40 secs.

Thanks, bit early for sums lol, kettle took exactly  2 mins to boil four cups .
.
Kettle used was a very good Tower model T10023   , the first I ve seen with a flat bottom allowing just a half pint mug .Watts was 2520-3000

Its not worth the faff to save 40 secs messing about with a flask IMO  and getting an inferior cuppa out of the flask .

May just as well boil four separate  cups . Needs one of those flat bottom kettles though