Solar Panel Installation

What would be the better option - Is it better to install solar on Duplex units from builder (3kw $3500-$5500 per unit) or hire a solar company later to install this ? I know it can be little bit lesser, but heard many stories about installation on the roof and damaging it, etc. Please suggest the nominal price range for 3kw instllation with panels, invertors, batteries.

I'd usually recommend using a separate solar installer, not the builder. You'll have more control on the quality of the installation (if you do your research), as the builder could be getting anyone to do the installation.

I'd recommend using Solar Quotes to get quotes from 3 verified companies local to your area. You want to choose a company that's well reviewed, has been in the solar game for many years, is quite local to your area, & is happy to come on site as part of the quoting process (to get a better idea of your roof layout & any shading issues).

I'd try to organise an installation company fairly early in the build. If they're not allowed to do the solar installation while the build is still underway, I'd at least ask for their input, so you can get the builder to run the appropriate conduits etc, so the solar install will be neat.

Solar Quotes also has a wealth of information in their blogs.

Firstly, their Solar 101 guide,
https://www.solarquotes.com.au/solar101.html

Also one on the brands of panel & inverters they trust,
https://www.solarquotes.com.au/solar-brands-trust.html

From batteries, 3 phase power, different panel layouts, scheduling your hot water heating to use solar power..... there's far more useful information at Solar Quotes than I can write here.

For solar, the most important aspects in order are;
1. Quality of the installer.
2. Quality of the inverter.
3. Quality of the panels.

So don't choose the cheapest quote you find in an ad, you get what you pay for. A cheap quote usually means a poor quality install, using poor quality gear. With the builder,.... you have no control over the subcontractor, so little control over the install.

So, 3 quotes from Solar Quotes.

If you have no issues with shading, a string inverter will be fine. The best string inverter is Fronius, but you may also be happy with something a bit cheaper like Sungrow.

If you have shading (or a very complex roof) you may instead need micro-inverters from Enphase or optimisers from SolarEdge. These will be more expensive than a string inverter like Fronius, so unnecessary for a simple unshaded roof.

Panels. You could go for premium panels from brands like Sun Power or REC, but you'll pay for them. As I said, panel quality isn't so critical. You don't want junk, but most people don't need the best. Most will be happy with cheaper, value panels (often Chinese) from the likes of Jinko, Trina or Longi.

Prices depend on your location. Victoria has more generous rebates & loans than other states.

But generally solar has been approaching about $1 per watt. So around $6,000 for a 6.6kW system (the most common size). Not sure how inflation has effected prices over the last few months.

Is 3kW the largest system you'll comfortably fit on each duplex? Smaller systems will cost more per watt. It may be better to go a bit larger, if they'll fit, future-proofing your homes. This means building all-electric homes, with no gas connections.

Reverse cycle AC to heat (& cool at times), the cheapest way to heat a home. Heat pump hot water, extremely energy efficient. Induction cooking, sensitive, faster than gas, without the mess to clean or indoor air quality issues. Installing 32A power circuits (if you're not 3 phase) in the garage, as we'll be driving Evs soon.

With a good-sized solar PV system to power it all.

Homeone isn't the best place to come for this advice, it's not too green minded.

If you're on Facebook, I recommend joining the My Efficient Electric Home (MEEH) group. For information on solar, & ditching gas in favour of an all-electric home.

oh, & at this stage, unless you can get very generous rebates, batteries still aren't worth the investment. With payback periods of at least 10 years. So I'd hold off the batteries for now. In any case, your EV may become your mobile home battery, as we move to V2G (vehicle-to-grid) & V2H (vehicle-to-home) technology. The battery in EVs much larger than home batteries.

That's great information ddarroch, referring to your whole post, but I didn't understand the above comment.

Are you saying 32A circuits for EVs are not required if you have 3 phase?

[quote="RustedOn":36to5jl1][quote="ddarroch":36to5jl1]Installing 32A power circuits (if your not 3 phase) in the garage, as we'll be driving Evs soon.[/quote:36to5jl1]
That's great information ddarroch, referring to your whole post, but I didn't understand the above comment.

Are you saying 32A circuits for EVs are not required if you have 3 phase?[/quote:36to5jl1]

Firstly, I'm not an expert.

But a normal, single phase 10A power point will charge at a rate of 2.4kW. So a 60kWh EV battery will take 25 hours to fully charge from flat to full. Too long for most people.

Use a single phase 32A plug, & you can charge at 7.6kW. That 60kWh battery will charge in just under 8 hours. So acceptable for many people, whether charging overnight, or with solar on a sunny weekend.

Again, not an expert. But 3 phase power will charge 3 times faster. So a 10A 3 phase plug will charge at 7.2kW. So a very similar rate to 32A single phase. Recharging in just over 8 hours. So acceptable for many people.

Sure you can get a 3 phase circuit at 32A for very fast charging at 22kW. Recharging the 60kWh battery in under 3 hours. But at this stage, many cars won't recharge at 22kW AC, some limited to 11kW I believe.

There would be very few residential solar systems that could generate power at 22kW, so if charging at this rate, I'd expect some imported power to be needed.

Not an expert on chargers in any way, & don't know if they can be set up to only charge at rate using excess solar power. Also don't know the cost of chargers. Whether 3 phase chargers cost more, or chargers that charge at higher rates, or if there's smart chargers that can be set up to just use excess solar.

32A 3 phase may be good for future proofing. It may be good to have very fast AC charging when required. But even 10A or 15A 3 phase will be fast enough for many people on most occasions.

While 10A or 15A single phase will be too slow for most people. 32A a better idea for people limited to single phase power.

$3500 for a 3.3 kW setup?
Your builder is applying a markup of about 100% and is having a lend of you.
For that price you'd be able to install 6.6kW easily

This was two years ago. I'm sure the prices have dropped since then.

Also, if you get the builder to install/supply, they have the option to take the Gov. STCs.
Can add up to a couple of thousand in their pocket..