Energy Meter use or ornament?

[stillp]

definitely boiling

very likely the temp was about 100C

But for how long? Also look up stratification in microwaved liquids, that can apparently lead to temperatures above boiling.

 

[big-all]

its also worth remembering the experiment stopped when the water boiled
the only difference between the 2 timings was i used the clock on the microwave so will check the accuracy off the micro clock but expect it to be within 1 second

 

[ban-all-sheds]

same cup same amount same plug in monitor about 5 mins apart kettle first then microwave so same cold cup
its possible the micro water was a fraction colder but unlikely to effect the overall outcome

The cold cup will.

 

[big-all]

ok tried it with a clear pyrex jug took an extra 5 seconds to boil but you would expect that as the jug has a greater mass so that now rules it boiling earlier than seen in the micro and also the water drawn was now the first cup after 2hrs standing in the pipe
the micro clock was within one second

 

[big-all]

same cup same amount same plug in monitor about 5 mins apart kettle first then microwave so same cold cup
its possible the micro water was a fraction colder but unlikely to effect the overall outcome

The cold cup will.

but the experiment was boiling a cup full off water which requires a cup

 

[ban-all-sheds]

The reason I am doubtful about the kettle timing is that I recently decided to see how much it was costing me to do my preferred practice of boiling water to warm the mug, then boiling more to make the tea, for the same reason one warms a pot first.

With a 3kW (@240V) kettle, I could boil a mug-plus-a-bit-to-avoid-dregs-full from tap-fresh cold in about 70s. I could get it down to a bit less than that if I didn't mind risking scale coming out, or didn't mind having to wait for the last few dribbles to make it past the filter. [A 3kW kettle costs about 0.01p/s to run, BTW, so the answer was "less than a penny".]

OK - that was the time until the kettle switched off, and it would have been boiling for a bit before then, but not for 30s.

Remember it takes orders of magnitude more energy to boil water than just to get it to 100°. I know it will get no hotter, but the point is that kettles don't switch off at 100°, they switch off after the water has been boiling for a few seconds.

 

[ban-all-sheds]

but the experiment was boiling a cup full off water which requires a cup

It doesn't require a cup to boil it in a kettle. In a microwave oven you have to get the cup to 100° as well.

 

[Iggifer]

but the experiment was boiling a cup full off water which requires a cup

It doesn't require a cup to boil it in a kettle. In a microwave oven you have to get the cup to 100° as well.

Well, that's not necessarily true. The cup will get warm, yes, but provided it is of decent quality, it shouldn't heat to 100°C. The majority of plates/some mugs are microwave transparent, and as such any container you can use to heat food/drink with that does not get hotter than the contents, isn't absorbing microwaves. The plate/mug will heat up through conduction - much the same way the sides of the kettle do. Yes, it's a thermal loss, but no different to the losses from a kettle.

If your mug gets up to 100°C when you boil water in it. Don't do it.

 

[big-all]

but the experiment was boiling a cup full off water which requires a cup

It doesn't require a cup to boil it in a kettle. In a microwave oven you have to get the cup to 100° as well.

we then get into the finer detail off the argument
is there loss from contaminants in the microwave and heat transference between cup and turntable
also would covering the cup speed up the boiling
but because its around 30% cheaper in kettle its an experiment not needed

 

[ban-all-sheds]

Well, that's not necessarily true.

It pretty much is.

The cup will get warm, yes, but provided it is of decent quality, it shouldn't heat to 100°C.

If the water in it is to boil, then assuming a glass or ceramic container you're going to be heating that too.

The majority of plates/some mugs are microwave transparent, and as such any container you can use to heat food/drink with that does not get hotter than the contents, isn't absorbing microwaves.

Never said it was. But it will be absorbing the heat from the contents.

The plate/mug will heat up through conduction - much the same way the sides of the kettle do. Yes, it's a thermal loss, but no different to the losses from a kettle.

I'm happy to touch the outside of most kettles when they are boiling. Please let us know how you get on touching the outside of a glass or ceramic mug by the time you have made the water in it boil.

If your mug gets up to 100°C when you boil water in it. Don't do it.

It may not get to 100°C. But I'm sure it will absorb more heat than a designed-to-be-efficient kettle body will.

 

[ericmark]

No - sorry - I still simply don't get it. I cannot see why people need a monitor to tell them to switch things off which they are not using.

Perhaps because most people were not born with an inherent understanding of the relative energy cost of different appliances.

For example there are still people who think that turning off a lamp, or unplugging a phone charger, will make a discernible difference, or that it is cheaper to wash up by hand than in a dishwasher.

I used to have an old fridge and an old freezer. When I changed to new, my daily usage and electricity bill dropped significantly. The same happened with the washer and drier. If I had realised the cost of running the old appliances, I might have changed sooner and recouped the purchase price.

This is where I started to work out costs, I looked at the life of a fridge/freezer and it does seem from warranty offered the newer inverter models do last longer but of course cost more to start with so the only way is to compare to a cheap model so looking as £160 approx warranty 1 year but likely will last 5 years so £32 per year. As an example I am looking at this random model at 204 kWh x 16p a unit and purely by chance it actually works out that the cost to run is also £32 per year so the total is £64 per year to run. So unless the old fridge/freezer uses more than £64 pounds per year of power not worth replacing. So yes forgetting about interest on money then swapping a B class for a A+ class will break even anything below B class your gaining.

However that is the cheapest fridge/freezer, the freezer is manual defrost and that means the air is not circulated which in turn means not all the food will be at -18°C that near the door is likely a lot warmer, also you can't remove a draw to get Christmas turkey in as there are pipes in the way, plus the problem of de-frosting although the safety of ensuring all food at -18°C is in real terms more important. At £180 your starting to look at frost free but the rating also changes when using frost free so also jumping to 226 kWh so £36 + 36 = £72 per year now we are looking at class C fridge/freezer before it is worth replacing.

Now in my house to get my wife to accept the cheapest fridge/freezer is going to take some doing she will want one with bells and whistles so I was looking at £700 for a replacement OK this one has a display to tell you after a power cut what temperature it went up to and is class A++ but also bigger than the examples I selected so again no real saving.

In our case old fridge/freezer was insured so not too big of a hit on the expense side and the old one is still used for brewing my beer in. However the old one really has to be super inefficient for it to be ever worth replacing purely because it is an old model. I would say it is rare for a fridge/freezer to be worth replacing before it fails.

I worked all this out without measuring the fridge/freezer power use. I did test the new one and it was very close to what the advert stated. But all the data given as to how it is better to swap to a new economic model is based on the cheapest replacement.

So yes the energy meter plug in type can show you how much the fridge/freezer uses and will highlight when the insulation has failed and the unit is working overtime to keep the food cold. But that need the user to be able to work out what it should use. So you need to do the following.
1) Start a data base to record info.
2) Reset the energy meter to zero ready for new test and ensure batteries are good.
3) Note the time when you started test.
4) Note the time when you finished test.
5) Adjust all reading to a one year time scale.
Only then can you go to a web site and see how your fridge/freezer compares with a new one. Yes I can tell you what my fridge/freezer uses it worked out at 285 kWh/annum with a 288 litre fridge and a 112 litre freezer and it should have been 279 kWh/annum to be classed as A++ but we likely opened the door more times than the standard 5 times a day or the room was hotter or I started test just before motor starts to run and finished just after only tested for 36 hours.

In my case because it identified the problem with my mothers freezer that with my skills I could correct for around £5 it has likely paid for its self. But if I include the man hours spent doing the calculations then it must be costing money as in early years of ownership I being sad actually worked it out. So question who has actually worked out the energy used into kWh/Annum to be able to see if equipment was faulty or not?

 

[JohnW2]

which is quickest which is cheapest ... a 900w microwave and a mug off water ... or the same mug off water in a 2750 kettle ... answers please

The kettle will obviously be quicker. It will almost certainly also be cheaper, since it is close to 100% efficient, whereas there are multiple sources of inefficiency in a microwave.

Kind Regards, John

 

[ban-all-sheds]

Also look up stratification in microwaved liquids, that can apparently lead to temperatures above boiling.

And can be "interesting" when you stick a spoon in, or just jiggle the container a bit when removing it from the oven.

Strictly speaking though it does not lead to temperatures above boiling - the boiling point of a layer is raised because it's under pressure. Lowering the pressure leads to the BP falling below the temperature.

 

[stillp]

Strictly speaking though it does not lead to temperatures above boiling - the boiling point of a layer is raised because it's under pressure. Lowering the pressure leads to the BP falling below the temperature.

OK, I'll reword that: "that can apparently lead to temperatures above the usual boiling point of the liquid in question".

Damn, I've been out-pedanted.

 

[ericmark]

Kettles do the same, as I found out, boiled kettle poured into flask put on the top and picked it up to carry to next room by the body not carrying handle and it re-boiled forcing boiling water over my hand. It was one of those pump the top flasks that allow you to dispense the liquid without picking up the flash, my error was the flask had been pre-warmed.

I also compared the kettle to the hob, could not test hob with energy meter had to accept the rating declared my daughter demonstrated how much quicker the electric kettle was to using her gas hob, I was rather surprised that a 2.8kW kettle could beat a 5.5kW gas hob. So on returning home repeated the test. Filled kettle to mark, (2.8kW) and poured into a pan with lid, refilled kettle to mark and then switch on my 3kW induction hob on at the same time as the kettle. The kettle did win, but by a very small margin maybe one second. So clearly with an induction hob not worth boiling water in kettle and transferring, but with a slow gas hob it clearly was.

When people referred to now we are cooking on gas it did mean now we are moving faster, but that is no longer the case, today electric induction hobs are faster than gas in spite being half the size in power used.

As to kettle and micro wave I think the person who fills a cup with water and pours it into the kettle and boils just one cup of water is rare. I always re-fill the kettle after use so it is not switched on dry so in the main boiling the kettle means at least 4 cups of water are boiled, the micro wave is not used to make coffee but to re-heat coffee already made so to compare cost one would need to factor in the cost of coffee and milk. I suppose I could pour the coffee into a pan and re-heat but then the pan needs washing so have to factor in cost of space in the dish washer.