Is ducted air conditioning worth it?

[devank]

I’m trying to see if it is economical to run the ducted air conditioning overnight instead of two split systems.

Lets say a ducted air conditioning is about 22kw. Say it is used 9 hours a day (overnight usage), 91 days a year (half of winter and half of summer).

Smaller 4.2 kw system costs about $2000.00 to install. Say there are two bed rooms.

So the difference in kws = 22 – 4.2 x2 = 13.6kw

Cost savings per year = 13.6kw x $0.24 per hour x 9 hours x 91 days per year = $2680.00!

Installation cost can be recovered in just two days! Did I make a mistake with the calculation?

 

[Melbournian]

personally i could not feel the effect with ducted A/C compared with a traditional A/C but for heating yes.

 

[wylie]

We have ducted air but have recently installed two 2.5kW units in two bedrooms upstairs because on the odd night or day when we need cool or heat in just the bedrooms, it means running the big system, even if just the bedroom zones are on.

I've also just ordered a monitor to see what power we are using. This will be fitted in a couple of weeks and I'll be able to monitor how much power the ducted system uses compared to the two small bedroom units.

If you can wait a month, I can tell you what I find.

 

[dan c]

So the difference in kws = 22 – 4.2 x2 = 13.6kw

Cost savings per year = 13.6kw x $0.24 per hour x 9 hours x 91 days per year = $2680.00!

Installation cost can be recovered in just two days! Did I make a mistake with the calculation?

I think there's something wrong with your calculation. Our power bill wouldn't be $2680 for the year, for the whole house, and we have ducted heating and cooling.

 

[devank]

it means running the big system, even if just the bedroom zones are on.

I've also just ordered a monitor to see what power we are using.

I don't think switching on just one zone reduces the power consumption but you can heat up room faster and then switch off the system.

How do you connect those monitors? Generally air-cons are directly connected to the switch board aren't they?

I think there's something wrong with your calculation. Our power bill wouldn't be $2680 for the year, for the whole house, and we have ducted heating and cooling.

I think you are right
May be they don't need to run at their full capacity all the time. Wylie's measurement can be more helpful.

 

[vaughan]

We have ducted heating in or PPOR and LOVE it. Only problem is that the whole house gets heated, which is inefficient if say only one person is home.

System can be installed that allow zoning so that the air can be diverted to or away from certain rooms. Adds a lots to the price.

 

[wylie]

We have to get our sparky in to hook it up. He says it is very quick and easy.

 

[intrigued]

I’m trying to see if it is economical to run the ducted air conditioning overnight instead of two split systems.

Lets say a ducted air conditioning is about 22kw. Say it is used 9 hours a day (overnight usage), 91 days a year (half of winter and half of summer).

Smaller 4.2 kw system costs about $2000.00 to install. Say there are two bed rooms.

So the difference in kws = 22 – 4.2 x2 = 13.6kw

Cost savings per year = 13.6kw x $0.24 per hour x 9 hours x 91 days per year = $2680.00!

Installation cost can be recovered in just two days! Did I make a mistake with the calculation?

Yes
You are looking at outputs (refrigeration capacity) you need the input power at certain conditions to work out power cost.
An inverter type air conditioner with zoning or closed doors will be as effective power wise though only slightly higher because of losses in the inverter.
The inverter only uses the power required, if that makes sense as it will slow down, the costs difference would be minimal.
But if it is not inverted then it’s worth talking about.

 

[wylie]

I've just organised for our monitor to be installed the week after next. I'm happy to turn on the ducted (not an inverter system - twelve or so years old) and then turn on two splits and see how much power they each use and report back.

We are going away for a week, so if I forget, give me a PM to remind me?

 

[intrigued]

I've just organised for our monitor to be installed the week after next. I'm happy to turn on the ducted (not an inverter system - twelve or so years old) and then turn on two splits and see how much power they each use and report back.

We are going away for a week, so if I forget, give me a PM to remind me?

Wylie

Don't you have a power meter ??????????????????

 

[devank]

You want him to switch off everything and measure the AirCon only?

 

[intrigued]

You want him to switch off everything and measure the AirCon only?

That will do it.

 

[wylie]

Wylie

Don't you have a power meter ??????????????????

You mean at the mains box? Of course I do (silly billy ) but my new monitor means I don't have to stand downstairs, outside in the cold whilst I shout to someone "turn off the a/c" and "turn on the splits".

My new "thingy" can come into the rooms with me and tell me how many cents it is costing or how many watts (or whatever they are called) I am using as I turn each thing on. It's going to be my new toy . I'm not sure how I would read the meter at the power box?

 

[BayView]

In our new PPoR we had no option due to roof design and concrete slab...

split systems.

We were advised (by the installer - electrician) to leave them on all the time (in winter), with the temp set at XYZ.

So far it has been terrific; our house is 6 star energy rated, so what I've noticed is that they re off much of the time, and kick in now and again to "top up" the temp.

In summer (just past) we hardly used them for cooling; used the airflows, and the insulation did the rest.

 

[BMan]

I don't think switching on just one zone reduces the power consumption but you can heat up room faster and then switch off the system.

there are some new ones that changes its output depending on how many zones you have running

I'm not sure how I would read the meter at the power box?

especially with the digital meters thay are starting to put in i wouldnt have a clue whats its doing except using more electricity

 

[Corey Batt]

especially with the digital meters thay are starting to put in i wouldnt have a clue whats its doing except using more electricity

I like my meter, press the button and tells me I'm producing more than using.

If you really want to go down the most cost effective route for cooling, go the good ol' evap. Newer models aren't that bad actually.

Doesn't put you in a good position for heating however.... Unless you like blankets.

 

[Jacque]

With the cost of our last electricity bill we'll be using the blankets and ugg boots more and switching OFF our air con. Geez I'm still reeling..... that along with the costs of keeping three teens is killing me!

 

[boomtown]

With the cost of our last electricity bill we'll be using the blankets and ugg boots more and switching OFF our air con. Geez I'm still reeling..... that along with the costs of keeping three teens is killing me!

Don't blame it on the carbon tax or the ACCC will get you.

 

[Corey Batt]

With the cost of our last electricity bill we'll be using the blankets and ugg boots more and switching OFF our air con. Geez I'm still reeling..... that along with the costs of keeping three teens is killing me!

Ditch the kids and get the heating pumping.

 

[Jacque]

Ditch the kids and get the heating pumping.

Haha I love it
Unfortunately I believe they'll be with us for a few years yet... I read the other day that the average child is now staying home and dependent on their parents until age 24- only another 10 years to go!!