[Closed] Hot water for cooking?

Depends on how good each of them are......

I think a decent microwave might edge it. Get it boiling quickly then leave it to stand for 5mins then finish it off with another blast.

I'd never cook with water out of a combi boiler though otherwise I think that would win.

efficient: Gas from cold as you're only heating the water you need and the pan. Too many energy conversions with an electric kettle. GCH hot water means you have to heat a cylinder of water and/or all the pipework. UK hot water is also a bit dodgy for cooking- we found dead things in my mum and dad's hot water (not radiator) header tanks

From a purely energy perspective. the watts required to boil the water will remain constant regardless of the heat type. When cooking over the hob, there will be heat escaping to the atmosphere around the pan base where as a kettle will be 100% efficient - the only undesirable heat transfer which will occur is the body of water, through the kettle wall and to the atmosphere.

As to the cheapest method - your gas is likely to be ~2.5-3p/kWh and your electricity 12-13p/kWh - the hob will likely be cheaper to run.

What if you have an electric induction job?

Ground source heat pump

Kelly kettle. Sticks* are free!

*or waste wood/cardboard etc

I boil the water in the kettle. It's quicker. No idea of comparative cost .

Really high end magnifying glass. Might take a while though.

What I tend to do though is pre boil a couple of cups worth of water in the kettle depending on how much pasta I'm cooking, and finish it off on the hob as normal, throwing in some extra tap water as nesesary.

Dunno how good or bad that is in terms of power efficiency but it's more time efficient..

On a slight tangent, one thing that annoys me, not that it's my problem, but my dad will fill a kettle half full to make a cup of coffee.

Why! It takes longer and uses more leccy!

What Are you planning to buy with all the money you save once you solve this issue  ?

Still saving for a manatee shower curtain.

Scruff is correct, kettle is most energy efficient but gas is cheaper per kW/h. FWIW I use kettle to get water to temperature then put it on the hob to get a rolling boil.

Induction hob is still less efficient than a kettle unless you have insulated pots. Assuming the kettle is plastic of course.

Iirc a microwave is about the most efficient way of heating just about anything with a significant water content.

Nope the kettle wins. What ever did we do before Google and bored people with bandwidth?

https://www.treehugger.com/clean-technology/ask-pablo-electric-kettle-stove-or-microwave-oven.html

Oh and completely unrelated as you wouldn't heat water in a toaster unless you're a loon but, well, it seemed like a vague excuse to post this video again.

A kettle is more efficient if you disregard producing and transmitting the electricity.

I split 50:50 and sit on the fence but enjoy the quicker time to get water ready for pasta - half in the pan and half in the kettle 🙂

EDIT - actually it's more like 70:30 kettle:pan as the kettle is so much faster

What do you mean by efficient?  Energy efficient or speed?

My Dad used to teach electricians.  In teaching lessons about power, he'd calculate the heat required to boil water, and then because the kettle is a resistive load you can calculate the energy delivered by multiplying the time taken by the rating of the kettle.  They are about 98% efficient apparently.  Because when electrical things are inefficient, where does the energy go?  Heat.

Of course generating electricity from gas is only what, 40% efficient, but when you boil a pan of water tons of heat escapes up the sides, so I reckon the kettle still would win even including from source.

Sounded more like kettle for the win.  In which case - how can I keep a kettle going long enough to cook my pasta in it?

A kettle is more efficient if you disregard producing and transmitting the electricity.

Nope, still more efficient whatever way you slice it.

Kettle first then pan.

However Mrs Panic insists that pasta cooks faster from cold.

So I have to use a pan on the gas.

Mrs panic is correct, but only if the cooking from cold method I s compared to the cooking from boiling method, just using a pan on the gas to heat the water.

If comparing the Cooking from cold method, to cooking from boiling method (using boiled water from a kettle) then the kettle to pan method is much faster.

But how would a domestic version of a jetboil pan on the small gas burner compare to a kettle?  Reckon it must be pretty close?

Electricity has been decarbonised significantly (revised EST conversion factors have elec coming down and gas going up...). If you live in Scotland there’s a fair chance your electricity was generated by hydro or wind.

gas is a fossil fuel. It’s on its way out.

boiling in a kettle will be the most efficient.... (less losses as heat source is located within the kettle and the walls can be insulated (which you can’t do if the heat source is external)).

oh, I’d love to see you try getting boiling water from a GSHP pp! 🤣

Quooker and then onto hob.... instant.

Yeah - gshp will have a COP of around 3.5-5 depending on design and install quality so approx same cost as gas to get water to 40-45 deg C.  Try getting it any hotter (55 ish) and your COP will drop significantly so no advantage over a kettle.  And you’re only halfway at that point.

gas is a fossil fuel. It’s on its way out

Not a huge amount of wind around today, gas is going to be around for a few years yet as a backup. Old king coal is doing well the last few weeks, wholesale gas price is quite high.

https://www.gridwatch.templar.co.uk

Whilst that may be true its still a finite resource which is the point that was being made. And if its not windy most of Scotlands energy will be nuclear.

We don't have an electric kettle cos they're ugly, but boiling water on the (induction) hob on "boost" mode is more or less as quick.

gas is a fossil fuel. It’s on its way out.

We could switch to methane. Harness the power of cow farts.

oh, I’d love to see you try getting boiling water from a GSHP pp

Depends very much on which bit of ground you use for your heat source.

Bits of Hawaii, Iceland or Yellowstone Park might yield impressive results

We could switch to methane. Harness the power of cow farts.

Common misconception, most of the methane produced by a cow comes out as burps. At least that makes the collection method cleaner albeit problematic if you want them to continue generating.

However Mrs Panic insists that pasta cooks faster from cold.

WHAT? Is that a thing?

Of course generating electricity from gas is only what, 40% efficient,

Much better than that from a modern CCGT plant, although you do then have transmission losses.

A modern condensing boiler will be ~90% efficient, and it won't have any transmission losses, however you will have to heat the water in the pipe between your boiler and your tap, so it depends how much water you're boiling. You could always recover this so it was only thermal losses into the pipe itself by turning the boiler off and running the rest of the hot water out of the tap... Also, it won't boil the water, only bring it to 60°C or so.

Of course if you use a kettle on a sunny, windy day it'll be drawing a significant amount of energy from renewables.

And if you wanted to be efficient you would get a heat pump to heat your water rather than just using electricity for heat.

I’d never cook with water out of a combi boiler though

Why?  There's no header tank, it's coming straight off the cold supply then heated, you're then going to boil it in a pan which is going to kill any bacteria (that are no more likely to be lurking in your hot pipes and taps than the cold)

Surely induction best here -  Gas hobs throw loads of waste heat into the room.  You're not going to cook in the kettle so you lose a load of energy transferring the hot water into the pan to cook.   Some kettles are insualted, but not all, so you've got losses to the room through the kettle walls.  Yes, you have losses from the pan walls but an induction hob will boil a lot quicker than the kettle so the losses are over a shorter time.

Hot water from the tap to start is often very wasteful depending on how long the pipe from the hot tank is - you potentially waste more hot water than you use as the stuff that sits in the pipe after you turn off loses it's heat the house.

Nope, still more efficient whatever way you slice it.

I look forward to your evidence for this assertion.

gas is a fossil fuel. It’s on its way out.

Mostly. But you can buy biomethane, produced from sewage sludge and food waste. The gas grid also has significant potential for hydrogen distribution.

However Mrs Panic insists that pasta cooks faster from cold

WHAT? Is that a thing?

Its true.

If you are going to use only a pan to heat the water to boiling point. Then the pasta will be ready sooner if you put it in straight away to the cold water. Rather than wait till the water is boiling before putting it in.

Makes total sense really, as the pasta is getting the absorption and starting to cook way before the water is boiling.

Its true.

That's not cooking faster though; just starting earlier

presumably if you just left some pasta in water at room temperature it would eventually 'cook' (ie become soft enough to eat)?

so maybe that's the most efficient way?

put it on the hob to get a rolling boil.

Whoa tiger. You're introducing a whole new world of issues there. Up until the point where it starts to boil you've only got your c m delta T to worry about.

If you're encouraging it to rolling boil then the latent heat of evaporation comes into play. And you don't want that. No sirreee.

I look forward to your evidence for this assertion.

I look forward to finding it, I know I have it in a book but a quick skim isn't showing it up. Anyway, in the meantime I found this:

https://protonsforbreakfast.wordpress.com/2012/12/16/which-kettle-to-choose-gas-or-electric/

Which confirms electricity is by far the most efficient at source. What that doesn't take into account is that, compared to the USA, we have far more efficient generation with more renewables and higher effiency of thermal generation (CCGT, nuclear etc.) per capita meaning the overall efficiency will be higher so I would expect electricity to be further ahead of gas on his chart.

I do have the material somewhere as I remember it coming up in my Energy Efficiency and Sustainability module I did a few years back. Gas is cheaper but terribly inefficient. Hydrogen can only be added in limited amounts otherwise a) you would need to change all your appliances or at least the burners like when we moved away from coal gas and b) the grid infrastructure isn't gas tight enough for hydrogen, it leaks like a bitch and is a total pain to work with. Pretty sure it can do nasty things to plastic pipework as well. Which is a shame as it would be great if we could just pipe that instead.

Also, whoever said there aren't transmission losses with gas, not sure how you think it keeps it's pressure otherwise.

you live in Scotland there’s a fair chance your electricity was generated by hydro or wind.

Isnt it shared on the grid?

A colleague with too much time on his hands measured the energy consumption of microwaves VS their cooking times.

They use more energy running the power supply and clock 24/7 than they used for cooking!

No idea if that still holds true now that appliances on standby have to use <1W, but a clock isn't technically a standby mode, it's on!