ECO kettle - I don't get it

stanstedpete

There are many sites where you can learn about heat pumps. This one has a calculator:

Heat Pump efficiency calculator

danmc_82

You miss my point, You cant produce more energy than what is being used to power it. Remember Einsteins quote.

And remember heat pumps only work in very insulated homes due to the lower temperature of the water.

stanstedpete

The COP (Coefficient of Performance) is the ratio between the electrical energy going in and the heat coming out. Typically it will be 2 or 3 but heat pump manufacturers typically quote 4. Follow up the link I posted earlier to learn more.

Insulation is not the issue - it's the type of heating. Underfloor heating is best, radiators really aren't suitable.

johntheexpat

Kettles aren't 100% efficient in the sense that you nearly always boil more water than necessary.  Therefore boiling the excess water is inefficient.  If you have twice the volume of water in the kettle than your mug will hold, then you are using 100% more electricity to make your cuppa than you need to.

They are also not 100% efficient because generating electricity isn't 100% efficient, more like 40%.  So it is a 60% loss to start with.  (It may not be you losing it, but it still counts).  And then there are transmission losses too.

Gas may do better, but there are also significant transmission losses there.  (The stuff comes, in part, from the other side of Russia, for goodness sake, it must take quite a lot of energy to get it half way across the planet.)

If you want an environmentally friendly cuppa, there is a lot to be said for a Kelly Kettle

Kelly Kettle® - Original & Best | Camping equipment | Camping gear | Survival kit - Home

Just use some scraps of wood that are only going to decay anyway.  No fossil fuel, no transmission losses and if you are having to collect sticks to boil a kettle, you take more care no over-filling it with water you won't use.

riseabdn

If you conccider the efficincy of a kettle is a function of the energy consumed during the boiling period against the energy gained by the water.

In boiling the kettle, you will also:
Produce sound
Warm up the work surface
Have heat loss though the sides
Heat loss via evaportation

to name but a few.

Sadly, the marketing people believe a 1kW kettle is half the cost to run of a 2kW kettle and i a massive 1/3rd the cost to run of a 3kW kettle.

If you concidder that one of the largest losses of the kettle after evaporation is heat losses from the side of the kettle.

If you remember the loss is related to the Delta-T (temperature difference) between the hot thing and cold thing.
This loss can be expressed in Watts of power which over time becomes energy in watt-hours, or watt-minutes in the case of a kettle.

If we agree that a 1.5kW kettle heats water from 10C to 95C, just as a 3kW kettle heats water from 10C to 95C.

If both kettles also had the same degree of heat loss,  measured in W/K (1 K = kelvin = 1C of temperature difference).

If both kettles were boiled at the same ambient temperature, then you will have a temperature difference (between the water and room) gradient.

The greater the time it takes the kettle to boiler, will mean this gradient exists for longer so the losses are greater.

As a result, if you run it though with numbers (real or for the sake of arguments), you find its more efficient to boil the water as quickly as possible from a point of view of case losses.

An ideal kettle would be well insulated (nobody seams to insulate kettles!) and operate around the maximum a 13A socket could take, i.e 2.86 to 3.25kW.

If the discussion even needs to come down to losses in the wiring in the house, then the street then the power station then its such a fine line as to make no difference at all.

That said, when designing the power network in, say, a hotel.  That horrible 700w kettle can save £10's of thousands on the grid connection costs when the engineer works out the diversity loadings.

Lower power kettles would also make life easier for these guys : BBC video on 1 million kettles


Stuart

stanstedpete

It is - or certainly was - possible to buy an insulated electric kettle (I used to have one). This improves efficiency by limiting heat loss during boiling and also afterwards (if more water than needed has been boiled - either inadvertently or because less than the minimum was needed).

Sound is a factor, but a relatively minor one. Evaporation is more of a problem, but is limited by having a kettle that shuts off promptly when boiling point is reach.

A bigger potential saving can be made by using a kettle that will switch off at a given temperature - if you're making coffee you don't want the water to be at 100C. However when Which? reviewed a kettle with a thermostat they found it was inaccurate. Good idea, though.

Something else to consider is that water for drinking is usually drawn from the mains, typically at 10-15C. If the ambient temperature is warmer than this there's a potential saving from filling the kettle in advance (or filling a jug) and allowing it to warm.

riseabdn

At a company i used to work for, we had a normal stainless steel kettle and my college was really bad for boiling the full thing, making a phone call whilst the kettle was boiling then forget about it.

After the thing was boiled 4 times without ever having been poured one day, i took some high temperature solar thermal insulation and used an epoxy adhesive to glue a 20mm thick layer around the kettle.   

An hour after boiling, the thing was still hot enough to make a cuppa.   I remember looking into developing it as a product but had no idea how at the time.

DF Eco Worrier

Best option is getting into good habits with support from the right technology. The good habits are all to do with not overfilling kettles and boiling only what you need. The right technology is to includes minimizing losses through good energy rating, double wall insulation and temperature control. Some drinks don't need water at 100 deg C such as green tea, speciality teas and instant coffee so temperature setting is good.

For example a 3 Kw kettle in use for 30 minutes a day, unit cost 10 p will costs about £55 per year to run.