1600 W maximum on vacuum cleaners from from Sept!

[peterb]

There is always a trade off between efficiency and convenience though. The most efficient way to heat domestic hot water is with an instant gas water heater and do away with the hot water tank completely. But flow rates tend to be lower, and the tank in a cupboard is good for airing/final drying of clothes.

As for reducing the power of electric kettles, that makes no sense at all as the energy required will be the same, so you will be using a lower wattage device for longer (energy being power x time).

The one proviso I'd add is that most people tend to overfill kettles to boil more than they immediately need, so there is a potential saving there, but for many people it will just be an inconvenience.

[kalniel]

However, I do recall a couple of years ago, it was very difficult to track down a kettle which can boil as little as one cup.

Nah it's easy

http://www.amazon.co.uk/Philips-HD46...ywords=Philips

That's been on sale from Amazon since 2008, and we've been using one for a few years, been brilliant.

[Zak33]

Had a similar argument last time I purchased a washing machine. Only really expensive ones have a hot water feed these days. The salesman gave me a load of crud about how it was more efficient to heat water in the appliance, which I pointed out was irrelevant as gas was so much cheaper that I was better off using the big tank of already hot water and wasting a bit. Was surprised no-one had picked him up on that before.

ahhh now you might have been wrong on that one chap

you see, and this is theory buy I think I have my theory very good here...

the amount of hot water used by a washing machine in the modern day is very low.. the total amount of water used is low.

The hot water in your tank isn't right next to your washing machine. It is many many meters away from it, in my house probably 20 metres of pipe away.

When you run a hot tap, how much water comes through before it's hot on your hand?

Possibly it's the amount that the washing machine takes for a normal wash.

If that's the case, you've drained the hot water from the tank, topping it up with cold. Boiler has to work again
You've filled your washer with cold to luke warm water and it still needs to heat it....

and you've filled metres of pipe with hot water which will, in theory partly heat your house but is certainly not totally all in your washing machine.

Cold inlet only is the way forward really, unless you have a large load and you're doing numerous washes per day so the pipes stay hot and the water is used hot from the tank

and of course.. assuming, your hot water boiler is efficient and not old and out of date.



What do you think? Good theory?

[Zak33]

Nah it's easy

http://www.amazon.co.uk/Philips-HD46...ywords=Philips

That's been on sale from Amazon since 2008, and we've been using one for a few years, been brilliant.

that's what I've got.. though the lid hinge pin on one side is broken now.. but still excellent kettle

[kalniel]

What do you think? Good theory?

Hehe well in my case the washing machine is right under the boiler, and a minimum of plumbing. Taking any residually warm water from the hot pipe means less work for the machine to do (it only has to get tepid for most washes anyway) and the boiler in eco mode won't fire on demand unless there's a continual drain on the hot tap. But the washing machine doesn't waste water waiting for it to get hot - it just takes water and if it's not at the right temperature, heats it further.

But there's the economic argument too - even if you're in a different situation and having wasting heat in lengthy plumbing, it might still be cheaper to use a boiler to heat the water for washing. (At the moment)

[Zak33]

my hot water tank is a long way in pipe terms to the washer.

In winter, when pipes are cold.. I can more than half fill my kitchen sink (plug in hole) from the hot tap before the water runs hot.

I think that's about as much water as my machine would use for a wash.. hence my theory

nicely warmed pipes all round the house... cold water in washer and cold water going back into hot water tank

[DanceswithUnix]

This was a pure speculation based on manufacturers claiming induction is the most efficient form of cooking.

For cooking on a hob that will be true. It is all down to how close to the food you can get the heat.

Traditional hob you create heat, and then try and transfer the heat to the pan by contact. You can finesse the design to minimise the heat escaping up the sides and back into the cooker, but the problem is getting the heat across the contact boundary & into the pan.

Induction hob, you induce eddy currents in the pan so the pan itself becomes the heat source. Neat stuff, a whole level of transfer avoided.

Microwaves directly heat the food, but that leads to a different type of cooking so don't really think it is comparable.

Thing with a kettle is that the element is already inside the water container and in direct contact with the water. So making a kettle efficient is pretty easy. Make it out of an insulating material so heat stays inside. Make the element right at the bottom so you don't need 3 mugs of water to protect the element when you only want to heat 1. Detect the steam fairly quickly so it doesn't bubble away for ages once the water has started boiling. I think anyone who has studied thermodynamics will see it is a rather good closed system with almost no room for improvement. The waste is the steam that gets out, and the water you don't use that you allow to go cold.

[DanceswithUnix]

What do you think? Good theory?

Lovely theory! The tank is upstairs in the middle of the house, next to the boiler. The run to the kitchen is probably quite direct, but still probably 10m of pipe.

Although in winter having another hot pipe in the house could be considered a bonus, specially in our rather cold kitchen

I think I went for a cold water inlet only one in the end, can't remember. Shame as I want to experiment with it now

[wasabi]

Pretty much all the modern washing machines don't have a warm intake from what i can see, just a cold. We used to have a hot intake on the old one - was surpried the super green Bosch one we ordered 6 months back didn't when I came to plumb in. Might have returned it to swap for a rare dual intake, but utility room is about 10m of pipework away from boiler so by the time the hot water had got to the machine the thing had filled with water anyway. Used to run hot tap in sink beside the washing machine before putting a load in which got a bit silly....

Most washes in the new Bosch come out really well on the 30 degree 49 minute sports wash setting anyway so better than the failed old clunker. Could I suppose run a shower mixer in front of the intake to keep the temp at 30 but seems overengineered.

[scaryjim]

... The most efficient way to heat domestic hot water is with an instant gas water heater and do away with the hot water tank completely. But flow rates tend to be lower ....

That's an interesting statement, given an issue we're currently having in a rented house: the shower in the bathroom mixes directly off the mains water feeds, and the cold feed has a flow restrictor on. Currently, no cold water gets to the shower, making it unusable unless you turn the hot water feed from the boiler down to minimum temperature. The guy who came to look at it was amazed that we didn't have a hot water tank - the whole point of the constrictor is that you get a lower flow rate from the tank, so you have to reduce the cold water pressure to match so the mixer tap can handle both feeds. I have to say I've never had any flow rate problems with the combis in the last few houses we've rented - always been very close to the cold water flow rate. I assume that's down to improved eficiency in modern boilers....

I believe I said about 4 pages ago that restricting kettles (and microwaves) would make no sense as the task energy for boiling a given amount of water is static (unlike the task energy for cleaning a carpet). Kettles are basically a solved problem.

Hm. I was just looking up gas diffuser rings (which I thought were meant to make gas rings more efficient, but are apparently about heating more evenly and presumably make the job less efficient by absorbing some of the generated heat), when I came across an "induction hob converter". Someone's had the great idea that induction hobs are efficient, but you need special pans for them, so why not find a way to use any pan on an induction hob? Brilliant, right? Apart from the solution is to stick a big lump of metal on top of the induction hob and put your pan on top of that - effectively turning your expensive, efficient induction hob into a normal electric hob. I'm gob-smacked....

[Top_gun]

So to do this boiling of water efficiently do I need a special pan?

I mean....do I use my smallest metal pan with lid on and just trust to the facts?

Because I always boil water for cooking....in my kettle and then into my steamer or pan which I heat with gas for a few seconds before pouring the kettle into it

I always do this and if I can save money by boiling water on the hob then I will

I think you can trust the facts. Make sure you choose a pot with a good thermal conductivity base like copper or aluminium. Mine is stainless steel with an aluminium to core to improve thermal conductivity. Also ensure, like others have said, the flame matches the pot size. Follow Jamie Oliver's advice on putting on the pot filled with water first before doing food prep. That way there's no waiting time before cooking.

Nah it's easy

http://www.amazon.co.uk/Philips-HD46...ywords=Philips

That's been on sale from Amazon since 2008, and we've been using one for a few years, been brilliant.

I have the same one too. The point I was trying to make is there are only a handful of kettles which can boil as little as one cup and the expensive ones like the Bosch seemed unreliable to me. The majority of kettles on the market have a minimum fill of two cups.

ETA: I've boycotted amazon but the same kettle could be bought elsewhere at a lower price.

[Noxvayl]

If only I could keep up with the frantic pace of discussion in this thread, I lose a couple pages every now and then

I enjoyed reading the comments about energy production and the electrical grid, saved the PDF to Evernote (cheers watercooled). The electrical system is an interest of mine so I might read some of the PDF at some point in the future.

One day I'll have the time to experiment with any and all appliances in the home but my parents would kill me if I did that with theirs. Old school African family that takes the no failure approach to teaching, very frustrating for me because I find failing so much more educational...

Nothing to chime in with on the majority of the discussion besides pointing out the most annoying sentence I have read in years, I will be sure to make the response only one paragraph to stop me ranting too much.

So I'm quite happily and readily admit, on this extremely very rare event, I could be wrong.

Wow, oh wow this is so arrogant I can't imagine why anyone would possibly construe your posts as being aggressive... You are wrong more often than you are right, no-one is exempt from this (not even the greatest of great people throughout history); during the course of your life that might only change after you are past your 30th birthday, only if you are EXTREMELY lucky like Isaac Newton- who practiced Alchemy despite being so right about physics (search Isaac Newton Alchemy, you can't make this stuff up). You haven't earned the ability to write that sentence without being called arrogant.

I feel better now, it feels somewhat therapeutic writing about yourself 6 years ago in response to someone elses post

[Top_gun]

You are wrong more often than you are right

Actually I assume I'm going to be wrong to 90% of the people all of the time. Why? It's because people formulate their views using different parameters. While I understand their parameters (and their limitations) they don't usually understand mine. Most people here have right wing tendency and I've simply moved on.

It's such a sad state of affairs where you take a really minor statement and turning into a drama. Good grief, is admitting being wrong really a sign of arrogance? Your first passive-aggressive attempt in trying to get me banned has failed and now you're trying to stir up trouble when it wasn't really necessary. What ever next?

[g8ina]

Steady chaps, no personal flaming, Id hate to close a fascinating thread such as this .... Who would have thought given that title that it would produce over five pages of responses.

[DanceswithUnix]

While I understand their parameters (and their limitations) they don't usually understand mine.

People are the same the world over. Give them some credit, you might be surprised.

Graphic example: The Barnum effect, giving people a detailed analysis of who they are written months before meeting them, wonderfully done across three continents by Derren: https://www.youtube.com/watch?v=2bCjzLij54k

Edit to add: Talk of limiting power in kettles reminds me of http://en.wikipedia.org/wiki/Dunning...3Kruger_effect

[peterb]

11 pages on a thread that was started about vacuum cleaner power inputs!