This isn't actually answering your question, but the below government website will be invaluable in designing a comfortable, energy efficient home.
https://www.yourhome.gov.au/passive-design
If you haven't already, get yourself…

What direction does the block face?
I wouldn't want a tree overshadowing my house badly in winter, or my solar PV system on the roof.
If the tree's to the west I'd…

Which way is north Varsity?
https://www.yourhome.gov.au/passive-design/orientation

As others have said, it could be a faulty appliance. Can't be faulty hot water (which is often the culprit), as it's gas, so won't effect the electricity bill.
If it's…

Just reading your OP again. You won't be using the main bathroom, or nobody will be using it?
Can I ask you family make up? Do you have kids? 3 of…

Capturing cooling breezes (by cross-ventilation) is extremely important in summer, particularly the further you get north in Australia.
On the Gold Coast these breezes come from the north east (to the…

Yes, a northern bedroom is always going to be warmer than a south facing bedroom, but not by a high degree.
It's not the northern bedroom windows that are the problem.…

Northern frontages always make it tough to build a comfortable, energy efficient home. Luckily you've got a nice big frontage, making thing easier.
Looking at the plan I'm guessing you've had…

Northern frontages always make it tough to build a comfortable, energy efficient home. Luckily you've got a nice big frontage, making thing easier.
Looking at the plan I'm guessing you've had…

Unfortunately wifey wants a gas cook top
Cheers,
Has she ever used a good quality induction cooktop? It's far more efficient than gas, gets up to temperature…

Sorry, I can answer your questions.
But I will offer some advice. Do your research about house plans, BEFORE you buy a block. Often people do this after they've bought a…

I'd ditch gas totally. Don't even connect it to your house in this day & age. You'll save money (no daily supply charges for the gas), & help save the…

I'd also consider a door, separating your living area from the hallway/stairway. As it stands, any heat you do gain in your living areas in winter time will be lost,…

As others have noted, I'd be worried about the western windows. Particularly the western master window. Eaves are quite ineffective at shading western & eastern windows, as the sun is…

Sorry, I wish I'd seen this thread earlier. As I'm going to make a negative comment, & it's probably (though maybe not) too late to make changes. Plus you may…

Yeah, don't rush the design phase OP. I'd also have a very good idea what I wanted to build, before even bidding on a property.
Not all blocks are really suitable,…

Agree with Bruce, great post! All things being equal, splits are more energy efficient than a ducted system. If you don't like the appearance of most wall mounted splits, there…

Thank you for taking the time to reply to my message.
Again as mentioned before our biggest issue, and the reason why we have decided to invest in DG is…

What climate are you in OP?
Firstly, I'd recommend reading this brilliant government website,
https://www.yourhome.gov.au/passive-design
Follow these principles & you'll have a home that is comfortable, light & bright…

As tourier says, it's important to make sure that you won't be overshadowed from the north.
You should be able to find out your council's rules on this quite easily, &…

A very important thing to consider is your home's orientation, & hence your block's orientation. This will have a huge impact on your home's comfort, & on your future heating/cooling…

You're very lucky to have a northern backyard, with a pretty wide frontage of 15 metres. Take advantage of this fact!
Neither of your plans do, wasting the northern aspect with…

They do say the 3 most important things to consider are location, location, location. But for me, that doesn't just mean the suburb, & the street, it actually means the…

Hebel, yes, better thermal properties than brick.
Steel frame no. Timber does the job, as long as termite protect is adequate. It's MUCH more sustainable (as long as it's sustainably sourced),…

What is the block's orientation Philsta?
For me, a home's orientation is EXTREMELY important. Getting northern sunlight into your living areas in winter, keeping the sun out in summer. Get this…

I'd agree that at the price we pay for double glazing (far higher than overseas I believe), it doesn't usually make financial sense. That money could be better utilised first…

As advised by SaveH2O, a hot water relay is a good idea. I haven't looked into them in about 12 months, but last I looked the stand alone ones (like…

As arcadelt has insinuated, much of your general heating should be done by the sun (as it's free), & powerful.
What we're talking about here is "passive solar design". Orientating your…