On 21/04/2017 12:23, NY wrote:
"Andy Burns" wrote in message
...
Even if all 220 million EU households bought a new vacuum that used
400W less than their old one and used it for 2 hours a month, it would
still be 2749.8 TWh

But *would* it still be for 2 hours a month. If you simply reduce the
motor power, without making that motor power produce more suction, all
you are doing is meaning that the device has to be left on longer to do
the same amount of work, because you have to keep going over the bits
that a stronger suction would have picked up first time.


Possibly - bit like an electric shower. But/and a fair bit of time -
when doing stairs for example - it isn't doing anything except making a
noise (unless you switch off between steps).

It's the same with kettles. It takes a fixed amount of energy to boil a
given amount of water, so if you reduce the power, the kettle must be
left on longer to boil that water - no saving of energy and certainly no
saving of time (quite the reverse).


No, kettles are pretty much 100% efficient. A hoover is nothing like
that - witness the noise for a start. 3kW kettles are a wonderful thing.

Better to encourage people to heat less water - don't boil a full kettle
if your teapot only holds half a kettle-full. Or else encourage people
to use the remaining hot water as part of the washing-up water.

Agreed. I don't use hot water much - household cleaning and very grubby
mitts. Most of the time cold does me fine.

--
Cheers, Rob