Energy myth-busting: Is it cheaper to have heating on all day?

Cardew

BikingBud said:

You'll be telling me I make coffee the wrong way next

In the spirit of this thread may I make the following suggestion:

If you make the coffee with cold water and then put the cup in a microwave to heat to your required temperature it is more efficient.

Making some assumptions I have calculated that a 3 cups a day person will save 4.12kWh a year!

Ultrasonic

Cardew said:

In the spirit of this thread may I make the following suggestion:

If you make the coffee with cold water and then put the cup in a microwave to heat to your required temperature it is more efficient.

Making some assumptions I have calculated that a 3 cups a day person will save 4.12kWh a year!

Are you sure? Microwave ovens aren't particularly efficient in terms of actually generating microwaves (~50 or 60% from quick Google) so whilst they'll just heat up the water in the mug rather than the body of the kettle I don't think it's a slam dunk which is better.

Ultrasonic

Data here to suggest using a kettle will use less electricity that a microwave to make coffee FWIW:

https://www.solarmill.com/blog/energyandcoffee

Cardew

Ultrasonic said:

Cardew said:

In the spirit of this thread may I make the following suggestion:

If you make the coffee with cold water and then put the cup in a microwave to heat to your required temperature it is more efficient.

Making some assumptions I have calculated that a 3 cups a day person will save 4.12kWh a year!

Are you sure? Microwave ovens aren't particularly efficient in terms of actually generating microwaves (~50 or 60% from quick Google) so whilst they'll just heat up the water in the mug rather than the body of the kettle I don't think it's a slam dunk which is better.

Thank You - good point, albeit in my defence I did state I had made some assumptions.

I will re-visit this burning issue; but I have yet to calculate exactly how much heat is wasted by heating the body of the kettle.

We could of course drink iced coffee.

BUFF

orrery said:

Spies said:

...the idea of optimisation is that the setpoint is reached at the time set on the thermostat vs it coming on at that time and then trying to get to the setpoint. 

I find that this doesn't work as it should. If I get out of bed at 7am then I don't need the temperature up at 21C (my normal room temperature). If the house is at 19.5 or 20C and the radiators are blazing hot, then the room will feel perfectly warm. Just as a room that is cooling, with radiators stone cold, and the thermostat at 19.5 or 20 feels cold. The proximity of the thermostat to walls that may be hotter or colder than the air in the room distorts the picture.

But, as you get to know how your system/habitation & personal comfort work, you can set a different set point for that time (assuming that your thermostat has enough set point/time slots).

BikingBud

Cardew said:

Ultrasonic said:

Cardew said:

In the spirit of this thread may I make the following suggestion:

If you make the coffee with cold water and then put the cup in a microwave to heat to your required temperature it is more efficient.

Making some assumptions I have calculated that a 3 cups a day person will save 4.12kWh a year!

Are you sure? Microwave ovens aren't particularly efficient in terms of actually generating microwaves (~50 or 60% from quick Google) so whilst they'll just heat up the water in the mug rather than the body of the kettle I don't think it's a slam dunk which is better.

Thank You - good point, albeit in my defence I did state I had made some assumptions.

I will re-visit this burning issue; but I have yet to calculate exactly how much heat is wasted by heating the body of the kettle.

We could of course drink iced coffee.

But the heat isn't wasted it contributes to warming the house  

As will the heat energy emitted by the magnetron

Ultrasonic

Cardew said:

Ultrasonic said:

Cardew said:

In the spirit of this thread may I make the following suggestion:

If you make the coffee with cold water and then put the cup in a microwave to heat to your required temperature it is more efficient.

Making some assumptions I have calculated that a 3 cups a day person will save 4.12kWh a year!

Are you sure? Microwave ovens aren't particularly efficient in terms of actually generating microwaves (~50 or 60% from quick Google) so whilst they'll just heat up the water in the mug rather than the body of the kettle I don't think it's a slam dunk which is better.

Thank You - good point, albeit in my defence I did state I had made some assumptions.

I will re-visit this burning issue; but I have yet to calculate exactly how much heat is wasted by heating the body of the kettle.

We could of course drink iced coffee.

I think we cross-posted. See the data in the link I posted above.

Ultrasonic

BikingBud said:

Cardew said:

Ultrasonic said:

Cardew said:

In the spirit of this thread may I make the following suggestion:

If you make the coffee with cold water and then put the cup in a microwave to heat to your required temperature it is more efficient.

Making some assumptions I have calculated that a 3 cups a day person will save 4.12kWh a year!

Are you sure? Microwave ovens aren't particularly efficient in terms of actually generating microwaves (~50 or 60% from quick Google) so whilst they'll just heat up the water in the mug rather than the body of the kettle I don't think it's a slam dunk which is better.

Thank You - good point, albeit in my defence I did state I had made some assumptions.

I will re-visit this burning issue; but I have yet to calculate exactly how much heat is wasted by heating the body of the kettle.

We could of course drink iced coffee.

But the heat isn't wasted it contributes to warming the house  

As will the heat energy emitted by the magnetron

Which might be helpful in winter but is wasted in summer.

Petriix

BikingBud said:

Petriix said:

You're still answering a different question from that posed in the title of the thread. And this is a great demonstration of why wet underfloor heating is so horribly inefficient: it's far too slow to adjust the air temperature so it demands that you keep a higher than necessary temperature at times when it's not needed.

So, you're right that there are circumstances where you will get more comfort from using (wasting) more energy. But, with a sensible heating system, you can optimise both. My thermostat uses a predictive algorithm and the weather forecast to ensure that the desired set point is reached at the desired time. If I go out, I set my return time and it ensures that the minimum energy is wasted in achieving my required comfort level.

There are further optimisations I could make if I installed smart TRVs throughout the house or adjusted the boiler, but none of those things negate the fundamental truth that the less time the boiler is running, the less energy it uses; and the more time the room thermostat spends set at a lower temperature, the less time the boiler will run for. 

Because the question in real life is not that simple.

You're comfortable or you're not!
 
How do you know what my comfort temp is?

Or my use case?

Have you lived with UFH?

Why would you need to adjust the temp rapidly? You miss the signifiant benefit of well designed and correctly set up UFH.

The same predictive algorithm can work for whichever system you want to install it's only a control system. How accurate are the weather predictions?

But like I said with an internet discussion like this everyone is correct and everyone else is wrong because their own interpretation and understanding and system demands are different.

You'll be telling me I make coffee the wrong way next

The laws of physics aren't subject to opinion.

You'd want to rapidly change the temperature so as to avoid wasting loads of energy heating an unoccupied house; by only adding the heat at the last minute before someone arrives home. If your heating system takes more a couple of hours to raise the air temperature by 5 degrees then you're forced into maintaining a higher temperature for longer and (objectively) losing more heat.

Spies

Temperature in my front room raises 1c per hour which I thought was the average?