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It is winter in Australia so heating and bills for it is on everyone's mind.

I was just trying to decide what method of keeping my house at reasonable temperature would be the best.

Suppose the total volume of heated premises is around 550 cubic meters, and if gas ducted heating is turned off, it cools down from 20 to 17 degrees in about 2 hours.

I could either turn heating on in short bursts getting the temperature up to around 22 degrees and then turning it off for a couple hours until it drops to 19-20. Otherwise, I could just keep heating constantly on at 19 or 20 degrees.

Which method is more efficient?

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The power needed is pretty much proportional to the difference between the  average outside + inside temperatures.

Heating the house to "too hot" is never efficient in this situation.

But the details may depend on other factors.

 

Incidentally, do you have air con + can it be reversed?

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1 hour ago, pavelcherepan said:

It is winter in Australia so heating and bills for it is on everyone's mind.

I was just trying to decide what method of keeping my house at reasonable temperature would be the best.

Suppose the total volume of heated premises is around 550 cubic meters, and if gas ducted heating is turned off, it cools down from 20 to 17 degrees in about 2 hours.

I could either turn heating on in short bursts getting the temperature up to around 22 degrees and then turning it off for a couple hours until it drops to 19-20. Otherwise, I could just keep heating constantly on at 19 or 20 degrees.

Which method is more efficient?

So you have a bit less than a pound of air in your house, which cools down from 293 to 290 K over 7200s, so basically you're heating with ca 200mW to keep it at 293K. I must be missing something...

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2 hours ago, YaDinghus said:

So you have a bit less than a pound of air in your house, which cools down from 293 to 290 K over 7200s, so basically you're heating with ca 200mW to keep it at 293K. I must be missing something...

Yes, about 155 pounds of air  !!

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3 hours ago, pavelcherepan said:

I have evaporative cooling for summer and gas ducted heating for winter.

 

Every time the gas heater fires up there is a flow of wasted gas until everything settles down to running conditions.

This is the same as the fuel used when cold starting a standard car is equivalent to consumption in the 5 - 15 mpg range.

 

In heating terms the phenomenon is known as boiler cycling (which you don't want)

So there is a trade off between tight control and lots of small inputs which waste fire up fuel and longer bursts which overheat more.

One solution is an intermediate buffer heat store.

 

 

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50 minutes ago, mistermack said:

Yes, about 155 pounds of air  !!

You know what, I missed the dimensionality of cubic meters. Thanks for catching that... So it's more like 200 W. That's a better ballpark, but it still seems low for winter heating. What's the outside temperature where you're at?

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1 minute ago, YaDinghus said:

You know what, I missed the dimensionality of cubic meters. Thanks for catching that... So it's more like 200 W. That's a better ballpark, but it still seems low for winter heating. What's the outside temperature where you're at?

It's hugely variable. The critical factors are not so much the temperatures, as firstly the quality of draught proofing, then the insulation. Only after that comes the type of heating and method. After all, if you don't lose any heat, you don't need any heat. You're only replacing what leaks away. 

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14 minutes ago, pavelcherepan said:

Depends on time of day of course. Between 4 degrees C and maybe 15 degrees on a good day.

You call that winter? :D

 

16 minutes ago, mistermack said:

It's hugely variable. The critical factors are not so much the temperatures, as firstly the quality of draught proofing, then the insulation. Only after that comes the type of heating and method. After all, if you don't lose any heat, you don't need any heat. You're only replacing what leaks away. 

Yeah... My parents got a new roof two years ago and that greatly reduced their gas consumption in the winter. Where they live it regularly goes below -10°C during the day and can reach -25°C at night. 

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1 hour ago, pavelcherepan said:

Australian winter, not a proper cold one, but then on the other hand, houses in Australia have absolutely garbage insulation.

A good insulation would also cut back on AC costs in the summer...

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