Boiling water

coffeehound

facade said:

Fast boil cordless kettles have a spring in the base that lifts the kettle up and stops it connecting if there is "insufficient" water to weigh it down. 

That's a clever idea.

Ultrasonic said:

BUFF said:

No, but a lot of (most?) electric kettles have a minimum level requirement which may be 500ml-1000ml so you could potentially be heating a lot more water than you actually need.

I use a graduated jug to measure my 300ml rather than weighing it. Alternatively, one could just fill one's cup & decant that into the kettle.

I do exactly the same with a measuring jug  .

I wonder what proportion of kettles in use today don't allow people to boil so little. The defining difference is I think whether a kettle has a flat bottom or a exposed coiled heating element - the latter needs to be covered with water and so sets a minimum fill level.

Flat bottom kettles take longer to heat up and continue putting out heat after switch-off; i.e. higher heat capacity, which must reduce their efficiency compared to curly elements, so swings and roundabouts.

For the morning coffee I eyeball water amount with a measuring jug and then weigh it as well.  Madness

Ultrasonic

Benny2020 said:

Isn't the temperature that the water starts from relevant?

Sure. What you proposed will be more energy efficient than just letting previously heated water go completely to waste but it will still be less efficient than just heating the right amount each time. The reason is the water will still need reheating to some degree. 

Benny2020

I think you and I both have solar arrays so our economics are a little different to most.

Ultrasonic

Benny2020 said:

I think you and I both have solar arrays so our economics are a little different to most.

Were you referring to me? If so then I don't have any solar panels I'm afraid. Something I maybe should look into but haven't.

Benny2020

Oh i thought you did, so how do you get your electricity consumption down to 4kWh a day? 
I have 4 kwp of solar panels and still take 3 kwh from the grid on average over a year.
Yesterday i made 18 kwh and still took 3 kwh from the grid.

Ultrasonic

Benny2020 said:

Oh i thought you did, so how do you get your electricity consumption down to 4kWh a day? 
I have 4 kwp of solar panels and still take 3 kwh from the grid on average over a year.
Yesterday i made 18 kwh and still took 3 kwh from the grid.

I live on my own so I don't think my use is especially low really? I've used about this amount on average over each of the last 5 years without going out of my way to do anything I'd view as special. I have an electric oven and hobs too or it could be lower. 

To give an actual number, form 04/03/21 to 04/03/22 I used an average of 3.79 kWh per day. Others here use less without the likes of solar panels.

JohnSwift10

Ultrasonic said:

JohnSwift10 said:

ProDave said:

I think you will find the cost of boiling the water for a few cups of tea each day is insignificant compared to the energy needed to heat your home in winter.  Being eficcient will chip a little off your bill, but is lost in the noise compared to the energy price rises recently.

Exactly, I used a monitor on my kettle for a day and boiling 2 cups of water 5 times a day and 2 full kettles twice a day used slightly less than 1 kW of electricity. 

I think you meant 1 kWh there, which is not an insignificant amount. About a quarter of my total daily electricity use in fact.

I think everyone knows what I mean but if it makes you happy to mention every time when someone misses the h then go for it.

Benny2020

"Exactly, I used a monitor on my kettle for a day and boiling 2 cups of water 5 times a day and 2 full kettles twice a day used slightly less than 1 kW of electricity."

Technically you also did not boil the cups.

BUFF

coffeehound said:

facade said:

Fast boil cordless kettles have a spring in the base that lifts the kettle up and stops it connecting if there is "insufficient" water to weigh it down. 

That's a clever idea.

but I am not sure that they all do that.

coffeehound said:

Flat bottom kettles take longer to heat up and continue putting out heat after switch-off; i.e. higher heat capacity, which must reduce their efficiency compared to curly elements, so swings and roundabouts.

& you think that curly elements instantly go cold when switched off? I wonder if anybody (presumably the manufacturers might have) has tested 2 identical kettle shells with the different styles of identical output element to see how they differ in energy use with the same volume of water? Tbh I suspect that any difference between the 2 in those conditions is miniscule.

Ultrasonic said:

Benny2020 said:

Oh i thought you did, so how do you get your electricity consumption down to 4kWh a day? 
I have 4 kwp of solar panels and still take 3 kwh from the grid on average over a year.
Yesterday i made 18 kwh and still took 3 kwh from the grid.

I live on my own so I don't think my use is especially low really? I've used about this amount on average over each of the last 5 years without going out of my way to do anything I'd view as special. I have an electric oven and hobs too or it could be lower. 

To give an actual number, form 04/03/21 to 04/03/22 I used an average of 3.79 kWh per day. Others here use less without the likes of solar panels.

Like Ultrasonic I live on my own, have no solar panels & my usage averages ~3.2kWh/day over the year (in Winter you can very definitely see the impact of the gas boiler pump running) . I would like to crack 1000kWh/year but suspect that is beyond me without some impact that I would rather not - nearest I have ever got was 1050kWh/year.

Marvel1

What about a 1 cup kettle? Fill to the max, in seconds gives 1 cup of boiled water.