Kettle energy efficiency
A environmentally concerned consumer asks
To boil the same volume of water, which is more energy efficient: a 3000 Watt kettle or a 2000 Watt kettle? I’m sure in a perfect experiment they should be identical in power consumption, but we do not live in such circumstances.
August 18th, 2008 at 1:36 pm
It will not be the same because resistance increases with heat, so consumption to deliver the extra watts will increase.
August 18th, 2008 at 1:45 pm
Am happy to announce that this is an area I am a complete and utter expert in! Infact I would say that there are very few folk who will know more about this than me.
2kw vs 3kw - no measurable difference what so ever though we did find that 3kw suffered more from overboil than 2kw (see point below).
The kettle design issues are as follows
1. overboil. The amount of time it takes for the kettle to stop heating the water once the water is boiling
2. heat loss. some of the heat from the element heats the air beneath the kettle rather than the water. This is very minor compared to point no1 but strangely you will find that more modern kettles have a plate element that sits on the bottom with one face not in contact with the water while older ones have a shaped element that sits in the water.
In reality it is not a design thing but more an “in use” thing. The “in use” issues are as follows
1. Boiling the correct volume. Seems obvious but this is the single most important consideration.
2. Re-boiling. Many people will boil a kettle, walk away and then come back to make the cup of tea and re-boil the water to ensure it is “at the correct temp”. Very inefficient
3. Fresh Water. Many users discard the kettles contents prior to starting a new boil - inefficient for obvious reasons.
Other considerations should be the embodied energy of the kettle itself. Buy a simple plastic kettle if you want to keep this low (and also the cost down!). Avoid Chrome or metal kettles.
August 18th, 2008 at 1:52 pm
And who ever spod is needs to do a bit of research! Yes resistance does increase inefficiency but it is the resistance of the material not the total resistance and the materials used have the same resistance be it a 2 or 3 or whatever KW kettle. Anyway, you can’t destroy energy so unless the inefficiency came out as light (and yes some muppet did invent a kettle that used light bulbs cause it looked pretty) then it has not been wasted as the inefficiency would come through as heat also! Go back to the physics class spod.
August 18th, 2008 at 1:56 pm
Please see ‘I heard a rumour’ below - the presentation of inaccurate information and rumour is not helpful. Point proven.
August 18th, 2008 at 2:08 pm
I think Spod might be on a bit of a mental safari!
August 18th, 2008 at 2:15 pm
Spod. Are you saying by being wrong you have proved a point? If only life was that simple!
August 18th, 2008 at 2:17 pm
Welcome to Alex Horne - nice of you to drop by.
August 18th, 2008 at 2:35 pm
I was trying to point out how easy it is to start a rumour. However, you scorched my rumour too fast for it to get started.