Fri, 10 Jul 2026 01:31:37 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91153#Comment_91153 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91153#Comment_91153 Tue, 05 Oct 2010 18:45:57 +0100 tony
I told her probably not but that it would make more difference how much too much water was boiled than any difference in efficiency

who was nearer?

I only drink cold water.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91155#Comment_91155 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91155#Comment_91155 Tue, 05 Oct 2010 20:14:35 +0100 bot de paille
or who was right for the sake of the marriage?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91157#Comment_91157 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91157#Comment_91157 Tue, 05 Oct 2010 20:39:18 +0100 brig001
On the other hand, my wife is almost never wrong
Brian.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91161#Comment_91161 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91161#Comment_91161 Tue, 05 Oct 2010 21:35:05 +0100 SteamyTea Put a litre in each, note the time they take to boil and look at the base of the kettle for the kW rating, find similar for the induction hob (or get an amp clamp). Do the sums. Be a very interesting study. You can do the same with a microwave (may need a special jug).]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91180#Comment_91180 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91180#Comment_91180 Tue, 05 Oct 2010 22:55:28 +0100 MarkBennett and:
http://withouthotair.blogspot.com/2009/11/how-to-boil-water-sequel.html

Intuitively, I would have to think that the kettle would be more efficient since it is essentially resistive and there are virtually no losses. In comparison an induction hob will have a substantial metal pan to heat up, (significant thermal mass compared to a plastic kettle!) which is probably wasted heat. However, a modern induction hob will be able to output more power (albeit less efficiently) and will be faster.

Making sure you only boil as much as needed is more likely to minimise energy usage, rather than how the heat is delivered.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91188#Comment_91188 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91188#Comment_91188 Wed, 06 Oct 2010 08:32:02 +0100 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91196#Comment_91196 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91196#Comment_91196 Wed, 06 Oct 2010 09:27:51 +0100 StuartB https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91202#Comment_91202 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91202#Comment_91202 Wed, 06 Oct 2010 10:03:25 +0100 MarkBennett Posted By: StuartBBoth are inefficient, the Tefal one cup uses the minimum amount of energy to 'boil' exactly what you need.

We tried one of these but it didn't produce hot enough water to make tea to the required quality (not me, I don't drink tea), annoyingly needed your attention for too long if you wanted more than a cupful, was noisy, needed dedicated filter cartridges and died within a couple of weeks.

Maybe the new ones are better, but we weren't at all impressed by our first generation model and were actually quite happy that it broke so we could get a refund.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91204#Comment_91204 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91204#Comment_91204 Wed, 06 Oct 2010 10:08:07 +0100 RobinB
I imagine the induction hob would be about the same for the same amount of water.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91205#Comment_91205 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91205#Comment_91205 Wed, 06 Oct 2010 10:08:41 +0100 evan
"Some more data: a 2.3kW plastic jug kettle (with flat base) required 102Wh to boil one cup, and a 3kW Tefal QuickCup hot water dispenser required only 28Wh for the same amount of water.

However, the water in the cup ended up 10 degrees C lower using the quick-cup machine. It was on the edge of being acceptable for a cup of tea. OTOH drinking scalding hot tea is pretty bad for you."

And yes, it broke after a couple of weeks, whereas the kettle is still working 2 years later.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91212#Comment_91212 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91212#Comment_91212 Wed, 06 Oct 2010 10:34:31 +0100 MarkBennett Posted By: evanAnd yes, it broke after a couple of weeks, whereas the kettle is still working 2 years later.

Hmm, seems like a trend. What's the embodied energy cost of a new QuickCup every two weeks compared to an extra 74Wh per cup? Discuss ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91218#Comment_91218 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91218#Comment_91218 Wed, 06 Oct 2010 11:28:58 +0100 DamonHD
As has been pointed out elsewhere, the embodied energy of any milk you add to that tea may well exceed the energy to boil the water, so be sparing with the milk.

http://www.earth.org.uk/food-and-CO2.html#cuppaCO2

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91219#Comment_91219 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91219#Comment_91219 Wed, 06 Oct 2010 11:32:36 +0100 SteamyTea This is also why lowering your internal house temperature by 1 C can save 20% on fuel (those using the C scale plays a part here).]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91220#Comment_91220 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91220#Comment_91220 Wed, 06 Oct 2010 11:34:43 +0100 DamonHD
Plus latent heat of vapourisation boiling water just to trigger the auto-switch-off when the water itself cannot get any hotter!

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91221#Comment_91221 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91221#Comment_91221 Wed, 06 Oct 2010 11:35:49 +0100 evan
This is also why lowering your internal house temperature by 1 C can save 20% on fuel (those using the C scale plays a part here).

That always amuses me. If you followed that advice every time you read some "energy saving tips", you'd end up with your thermostat set to minus several hundred :)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91225#Comment_91225 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91225#Comment_91225 Wed, 06 Oct 2010 12:14:50 +0100 DamonHD
Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91230#Comment_91230 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91230#Comment_91230 Wed, 06 Oct 2010 12:51:51 +0100 djh Posted By: SteamyTeaHeating water (or anything) follows an exponential curve. Hence it can take twice as much energy to raise it the final few degrees compared to the first (large) number of degrees.
This is also why lowering your internal house temperature by 1 C can save 20% on fuel (those using the C scale plays a part here).
Eh?!

Do you have a reference, for all three statements?

Yours enquiringly, Dave]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91235#Comment_91235 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91235#Comment_91235 Wed, 06 Oct 2010 13:27:14 +0100 Paul in Montreal Posted By: DamonHDThe rule of thumb I understood was 1C to save 10% presumbably on the the basis of an average delta-T/difference between inside and outside of 10C on heating days and a nice olde worlde linear releationship between deltaT and heat demand.

That's it exactly. When there's a delta-T of 40 or 45C over here I don't think about turning the thermostat down - if anything, it goes up a degree as the radiant cold from the windows feels uncomfortable when it's -25C or lower outside. Always be wary of any relationship expressed in percentages.

For those worrying about the energy required to make a cup of tea, so long as you only make your tea when it's cold outside, then all that "waste" heat will be useful anyway. As for the temperature of coffee, I believe the optimum is around 84C - but maybe that's just for espresso.

Paul in Montreal.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91240#Comment_91240 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91240#Comment_91240 Wed, 06 Oct 2010 13:35:41 +0100 DamonHD
Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91243#Comment_91243 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91243#Comment_91243 Wed, 06 Oct 2010 13:48:25 +0100 Paul in Montreal Posted By: DamonHDStill much better to heat my house with gas at 0.19kgCO2/kWh rather than waste electricity heat at over 0.5kgCO2/kWh in winter... (And indeed cheaper.)True - but it's probably better to use an electric kettle rather than one that sits on a gas hob. Really, I was just trying to point out that not all waste heat is really wasted. Personally, I don't drink tea anyway.

Paul in Montreal.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91244#Comment_91244 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91244#Comment_91244 Wed, 06 Oct 2010 13:48:48 +0100 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91249#Comment_91249 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91249#Comment_91249 Wed, 06 Oct 2010 15:06:58 +0100 SteamyTea
http://www.ugrad.math.ubc.ca/coursedoc/math100/notes/diffeqs/cool.html

Needs a bit of modification to make is applicable to heating because as something is heating it is also loosing heat, whereas if it is cooling it is only loosing heat. It can be described with a polynomial in the real world as there are set limits on it (freezing and boiling).

I use http://www.degreedays.net to calculate HDD at different base temperatures.
I will agree that 20% was a bit optimistic (I just plucked it from the air to highlight the issue).
But did a comparison between between 15C and 16C at Heathrow Airport and the total saving should be about 13% Reduction or 15% increase. Depends which way you want to work it. It also depends on other factors such as number of occupants, electrical goods generating heat i.e.Fridge/Freezer, solar gain etc.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91250#Comment_91250 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91250#Comment_91250 Wed, 06 Oct 2010 15:08:53 +0100 SteamyTea Posted By: Paul in MontrealPersonally, I don't drink tea anyway

Not even Yorkshire Tea. Tut Tut

Was told that coffee should be made between 88 and 94 C by the buyer at Pelican Rouge.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91254#Comment_91254 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91254#Comment_91254 Wed, 06 Oct 2010 15:25:15 +0100 gustyturbine https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91259#Comment_91259 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91259#Comment_91259 Wed, 06 Oct 2010 15:37:56 +0100 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91262#Comment_91262 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91262#Comment_91262 Wed, 06 Oct 2010 15:52:12 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91297#Comment_91297 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91297#Comment_91297 Wed, 06 Oct 2010 22:13:04 +0100 Hairlocks https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91299#Comment_91299 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91299#Comment_91299 Wed, 06 Oct 2010 22:31:01 +0100 Hairlocks https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91310#Comment_91310 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91310#Comment_91310 Thu, 07 Oct 2010 03:43:20 +0100 SteamyTea Posted By: Hairlockselectric Kettle used 50% +/- 5% of the energy of the gas hob and saucepan.
So cheaper and environmentally better to use saucepan on gas then.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91311#Comment_91311 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6379&Focus=91311#Comment_91311 Thu, 07 Oct 2010 03:57:44 +0100 DamonHD http://withouthotair.blogspot.com/2008/10/how-to-boil-water.html]]>