It’s still an upfront cost.

It is a bit like saying that Electric Vehicles only have about 0.5% of the market at present -- why doesn't everyone have an Electric Vehicle ?

Here in the city I live in , a large factory with 300 staff , has installed essentially the whole roof with solar panels , with a computerised system that tilts the panels etc . It was done during Covid lockdown , and is apparently going well -- so well that they hope to generate 100% of their power requirements over summer , but only about 20-25% over winter .

I know its different to domestic usage , but the figures quoted in a local business publication ( it didn't say how much the capital cost was ) said they are budgeting on a 10-12 year payback .

I have installed small systems in 3 of my properties , and my camper van , but they are more for information and because I like technology than straight $$$ reasons . For example , my camper with 4 panels , 2 large batteries as well as 2 'starting' batteries . regulators , an invertor , wiring , etc was well over $5000 ( and after 4 years , the batteries aren't totally stuffed , but will need replacing in the next couple of years at $800 each ) -- by comparison , a small generator to run the fridge , microwave and TV primarily would have been $1000-1500 , and maybe $100 a year in petrol for the use it gets .

If you are building your 6 bedroom 4 bathroom, four living area home. Yes you should have solar for all of your running costs.
But it should not be mandatory for new builds. It should be up to the new owner.
As an example: my power bill averages around $130 per month. We have a 347sqm home. We have built the home with good insulation, led lighting and orientation is correct for winter sun. If I spend say $6000 to $10000 on solar, less the max rebate of $3700 that means it is still costing me $2300 to $6300 up front. If I save 50% of my bill that is $65, that will take me 3 to 7 years to recoup my expenditure.
There are other factors in play. We are not home during the day on week days. Therefore our power usage is when the sun don't shine. We will definitely be keeping our look out for good battery storage options. But at the moment the solar sales people walk away when they see our bills. Again good battery storage is our priority for the way our house hold runs. Solar power is definitely a good thing, and if our personal situation changes we will revisit the costings. In the mean time, if your not in the room, turn the light off.
So in answer to your question. Yes install solar power. It is a good thing for the environment, and can save households a lot of money. But do not make it a mandatory new home build cost. The home should be built in the best possible way first, and individual circumstances taken into account.

Also, to take into consideration is the supply charge to be connected to the grid. For WA this is 93.933cents per day, so for my bill of $239.71, $57.30 plus gst was supply charges.
This is a charge that would be payable, even if we had solar. Because unless we go "off grid" we still have to pay.

Firstly OP, I believe the NSW government has no rebates for solar (except a minor trial for a low income rebate for solar in selected areas). Only a loan scheme.

The main rebate for solar is the STC rebate, which is a federal rebate.

Victoria has a state rebate, worth an additional $1,800 (plus another $1,800 as an interest-free loan), or there abouts.

But to the crux of your question.

If people have an unshaded roof, I think they'd be crazy not to invest in solar PV.

Technology has improved over the years, & prices have tumbled.

In most areas, single phase homes can have a solar system up to 6.66kW (5kW inverter) installed - any larger than this & export limiting will occur. A system this size can be installed for somewhere around a cost of $5,000 - $6,000. $3,500 to $4,500 in Victoria.

With savings on electricity of up to $1,500 a year, payback times average from 3 to 5 years.

After that is all profit. Tell we where you can find an investment with these sorts of returns. From you bank, shares, real-estate, I don't think so!

If I was building now, not only would I spend a lot of time getting the passive solar design right, & making sure my building envelope was well insulated & air tight (most new Aussie homes are very leaky). I'd also make sure my roof was well designed to accommodate solar panels.

This is often not the case in Australia, where we have a fascination for hip & valley tilled roofs. Hint: a rectangular panel doesn't fit well on a triangular roof face. A complex roof, with multiple angular roof faces, over many aspects, will reduce the available area for solar panels. It will complicate the installation, increasing costs. Plus the final result will look like a dog's breakfast.

But I'd be going much further than just installing solar panels. I'd be building an all-electric house.

Split system reverse cycle AC (heat pump), the most energy efficient, cost effective form of heating. Fans for cooling (AC is energy hungry for cooling).

Heat pump hot water, again, the most energy efficient way to heat water - unless you're in northern Australia, where solar thermal water is a good option also.

Induction cooking. As responsive as gas. But with even more control over temperature, & far, far easier to clean.

This means no gas to the home! A saving of over $300 a year, just in service charges alone! Plus cheaper running costs, especially when powered by solar PV.

Installing solar PV & saying no to gas is also far better for the environment.

The federal government may tell you that gas is a great transitional fuel, it's not! Why was the CO-VID Commission stacked with gas executives? Jobs for the boys, their fingers in the pie.

Not only does combustion of gas create quite a lot of carbon dioxide (about 50% as much as coal). But natural gas (methane) has a global warming potential of 25. That is, it's 25 times worse than carbon dioxide! This means that if only 3% of it leaks into the atmosphere during its extraction, processing or transportation, emissions are just as bad for gas as they are for coal!

Progressive government's like the ACT are considering banning natural gas from new developments. Other government's, who are too friendly with the fossil fuel industry, & are addicted to their political donations turn a blind eye to science & tell you gas is great!

For anyone on Facebook, who would like to build an energy efficient home, is recommend that join the 'My Efficient Electric Home' (MEEH) group.

@dreamer, you've made no mention of the feed-in-tariff (FIT).

Although I believe it is pitifully low in WA. As low as 3¢, where I believe it can still be found for up to 21¢ in other states (not too mention older systems, which may still be on much larger PFIT's).

In other states the FIT means solar PV is still a great option for people who are away from home for much of the day. Although I do see the FIT decreasing in all states, as solar increases, creating on oversupply of energy in the daytime.

By then hopefully battery storage costs will have decreased a lot. Currently batteries are far too expensive for them to make financial sense for a household.

But there may already be a great big big battery in your home, a thermal battery. Your hot water system!

Domestic hot water accounts for nearly a quarter of household energy use.

For those with solar PV (& excess power) who have electric hot water storage systems - either electric element or heat pump - it's a great idea to heat their water in the day time, with excess electricity from their solar PV. Other appliances should also be shifted to the day time. Washing machines, dishwashers, pool pumps.

Back to the topic of batteries. The WA government has put out tenders to install a battery system at the decommissioned Kwinana Power Station. This will be Australia's second largest battery!

Currently 1-in-3 WA household has solar PV. This is expected to grow to 1-in-2 over the next few years.

@ddarroch, yes FIT is 3cents then 10 cents between 3:00pm and 10pm. In WA.
Agree with everything in your comments. For us battery storage is the key. Thank you, for your comments across houzz. They are always informative and interesting.

It can really slash those monthly bills by wrangling heating, cooling, and other power needs. But, not all homes are jumping on the solar train.

I used to wonder the same thing. When we built our house last year, I was all for adding PV panels, but my spouse had reservations. They were worried about upfront costs and maintenance. We did some research and found that while the government rebate helped, it wasn't enough to sway them. Plus, they were concerned about the reliability of batteries like the Li Po battery for storage. In the end, we compromised: focusing on energy-efficient appliances and keeping an eye on future upgrades.

Most houses aren't built right and solar power is an addition to fix other shortcomings, which as noted comes with upfront costs and maintenance. Built right, plus solar power if and when you can add it, is far more effective. But the perception among homebuyers is solar is the first thing to do to make a home energy efficient?