Solar and Grid Connections

I am currently researching in preparation for a solar panel install. I understand that a new power company power meter must be installed to “isolate” your house from both the grid and your solar system. This is required under legislation.

This is ostensibly a safety measure to ensure the grid is not live from your feed-in. Fair enough. But the power meter also isolates your home from any power available from your panels.

I have 2 issues with this:
1/ its main purpose seems to be a revenue interlock to force a customer to pay a bill. Well now I am angry, I never default. In any case there are plenty of existing measure to recover funds without this type of bullying.
2/ technically it is very easy to prevent feed in when the grid is down given the smart meters in use these days (I am an engineer).

Simply put, I want my fridge and freezer to stay on when there is a day time power outage. Perhaps my reverse cycle air conditioner too if I have enough panels. Not an issue in low sunlight as inverters switch off when there is insufficient input.

I am therefore considering having dedicated solar circuits installed (retro fitted) to run those appliances during the day with the option to grid connect when I want. Of course there will now be no feed-in return funds plus tricky meter box but also my total power consumption reduces in compensation.

In this way the solar system works for me when it is most needed. I am South Australian and need to accommodate the supply uncertainty…

Do you or your members have any comment and advice?


I have had roof top solar for 10 years now and it is correct the systems are isolated when there is a power outage. It is a legal requirement, and as such you maybe fighting the ‘state’ to get changes to that requirement.

The alternative is a stand alone solar system with no grid connection then you do as you please, but they are still very expensive.

Lastly I would be concerned about a standalone solar during a power outage remaining on and powering my fridge and freezer as sudden cloud cover could cause a significant voltage drop and brownout damage to the electrical motors. IMO you would need a battery system as well to keep voltage adequate.


The meters only measure the power, they do not isolate the PV system or grid. You would have a net meter installed if you put a solar system on your roof now, it measured imports and exports after you use whatever is coming from your own system.
Inverters have a feature known as anti-islanding, which means they will disconnect from the grid if the grid goes down, this is to protect any line workers repairing the line.

If you want to still have power when the grid is down you will need a hybrid system that has a battery for backup power, and a suitable inverter that will operate in island mode- not all inverters will do this. Some models from companies such as Fronius, SMA and Australian manufacturer Selectronics have this feature. I believe the new Powerwall 2 from Tesla, soon to be available in Australia, will also have this feature.

Any attempt to make a grid-connect inverter work solely from panels when the grid is down is dangerous and unlikely to work in the way you hope- that type of inverter is designed to work at maximum rated output (as much as the PV panels will deliver) feeding a low impedance electricity grid, so if you only have a light load, where will the rest of the power go? If a cloud comes over and output drops, you can end up with burnt out motors.


Here is a couple of links with a bit more background on the Powerwall 2:


Here is an article on what can be expected with the right combination of Solar Panels and Batteries. At the end of the article it also states that the Powerwall 2 will be here around next month:


Many thanks for the info links Grahroll, useful and appreciated. Keep the info coming.
I have learned now that there are multiple “inverter-meter” modes available for PV from various suppliers, with one specifically catering for backup power when the grid is down, both with and without battery support.
And for Gordon, a PV array and or inverter without a load is not dangerous, just wasteful.

But overall I am satisfied that the installed cost of these things is now very affordable.


That’s not how a grid-connected inverter works, it shuts itself off (by law) once the grid is down. There is no supplying of loads unless it is a hybrid type inverter and there is a battery.
For an off-grid inverter, it also requires a battery, and only supplies to the demand of the load (up to its current or thermal limit), and when there is no load it sits idle, only consuming a small amount of power (for good quality inverters, cheap ebay junk wastes a lot).


I recently had a detailed quote on adding panels to my solar system and getting a battery unit connected to it. We currently have integrated panels on our roof which fit into the roof in place of tiles and do not stick on top - they look much better. He told me that the integrated panels I already had were not the best quality. I don’t know if he is right or whether he said that because his company can’t provide those integrated panels. He gave the quote and also several options for strange new systems that regulate your solar and supposedly save money.
My problem is the quote seemed high and his recommendations were totally beyond my expertise.
Is there any independent advice I can get re my solar system? Is there any group not affiliated with any particular brand who will give honestly impartial advice about solar systems?

I cannot vouch for the variability of advice, but you might join and use the whirlpool forums. Posts often attract some very good advice and experiences. Here is an example of how it goes -

Just be aware that there is also some terrible advice to be had there, and various trolls and vested interests, although the mods generally remove those posts after a few complaints.


Tesla have released information about their Solar Roof Tiles including warranty terms and pricing, see here:


They are taking deposits for solar roof tiles in Australia now, see:

However, at $42/sqft (US)* I think it will be an eye wateringly expensive way to cover your house in Australia, vs say Colorbond + regular PV panels. Of course some may like the look of them over regular panels, but personally I couldn’t justify that sort of expense.

*Thats over $600/sqm in $A terms, + the Australia tax!


They are not saying to cover your whole roof with percentages varying from about 35 to 70 percent of the roof actually having the Solar tiles the rest being non-solar (same looking tile but no solar component). The average house they think will be 40%. Check out the calculator, I used an address my sister had in Ca (2457 sq ft roof) and for there it was 50% Solar and it would cost about 67,000 + 7,000 (Powerwall 2) with a return of about $114,000 gross and $58,500 Net earned over 30 years.

Warranty as well being house’s lifetime or infinity for the tile surviving, 30 years on generation, and 30 years on weatherisation.

Apparently the average time in a home is 7.5 years. That clouds that actual cost benefit because whether it adds full, pro-rata, or little to no value on a sale in the interim is hard to quantify. Of course some of us stay put for decades, but.

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Quite a large proprtion of the population move house in just 5 years, so working on 30 year time frame for something that has been on the market for… well about -1 year at this stage!, is pretty dodgy

Not sure if you are working in $US, but anyway- $67000 would buy me a hell of a lot of PV panels to put over my Colorbond, and would be paid off in much quicker time. In any case, “a return of $114000 in 30 years” suggests a saving of $3800/year, which sounds like a lot of energy usage, just in savings, not gross usage- so supposedly saving about twice the total Aussie average electricity use.

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Yes it was $US dollars but the monthly usage was $240. The figures they provide can’t yet be changed to $AU’s as the calculator is purely US oriented at this time.

The 67K figure included "The estimated cost of your Solar Roof includes materials, installation, and the removal of your old roof. "

My bad usage of english but the $114,000 was the Gross Earnings of the panels over the 30 years of warrantied generation. The resultant Net $58,500 was after the cost of roof replacement, the install of the powerwall and some $18,000 tax credits they get in the US and it was obviously reducing the electricity bill to $0.

Yes covering your roof in panels would be cheaper and that is a very valid option but if you don’t want to install the panels and want a new roof then this may be an equally valid option and you would be getting a very resilient roof covering with a very long warranty period. As they won’t be in Australia until 2018 we still have time to see how they go and if the cost/benefit analysis is anywhere near accurate or not.

I hope they work as well as promised and if you were building a new house or having to replace your roof eg cyclone damage it certainly would be worth looking at them as an alternative if they are available.

If you had such a roof and you were selling (and could show the savings) then I think you would expect a premium on the price paid, a new owner would be saving on the electricity and would have roof tiles that were covered under a lifetime warranty.

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I never think roof tiles are a good option in areas of significant thunderstorm activity, given the size of hailstones frequently seen in storm season. I haven’t read their Oz warranty, so not sure if it would cover hail damage.


Yes they are offering the warranty US only at the moment but they expect similar Worldwide. “All warranties and ratings apply to the United States only. Similar warranties and ratings will be developed for other markets.”

Currently these are the ratings and such, maybe the ratings you could convert to relevant Au ones. They also have a video on the page and they use 2" hail stones hitting the panels at 100 mph.

Tile warranty
Infinity, or the lifetime of your house, whichever comes first

Power warranty
30 years

Weatherization warranty
30 years

Roof Pitch
3:12 to vertical

Hail rating
Class 4 FM 4473 (best hail rating)

Wind rating
Class F ASTM D3161 (best wind rating)

Fire rating
Class A UL 790 (best fire rating)

Glass Coating Standards
ASTM C1376 EN 1096 (best in class reliability)

The brackets around comments in the ratings are Tesla’s not mine :slight_smile:

Found this in relation to the Hail test from a US Roofing site:

"The Factory Mutual 4473 Test

The FM 4473 is another test used to test a roofing material’s ability to withstand damage. In this test, actual balls of ice are used on roofing materials. For the FM 4473 test, two inch balls of ice are shot at a speed of roughly 70 miles onto roofing materials. The Class 4 test is the most rigorous of all ice/hail tests and specimens are subject to impact anywhere from four to six times. As with the UL 2218 test, roofs must pass an extensive visual exam in order to pass the FM 4473. For a covering to receive a Class 4 rating, there must be no evidence of damage such as cracking or breaking."

ASTM Class F D3161:

“ASTM D3161, “ASTM D3161 / D3161M - 13 Standard Test Method for Wind-Resistance of Steep Slope Roofing Products (Fan-Induced Method) ,” applies to self-sealing and mechanically interlocking Steep Slope Roofing Products. During testing, test assemblies constructed according to shingle manufacturers’ installation instructions are subjected to fan-induced winds of specific velocities for specified durations. Based on the test results, shingles are classified as Class A when the test assembly passes a test wind velocity of 60 mph, Class D when the test assembly passes a test velocity of 90 mph and Class F when the test assembly passes a test velocity of 110 mph. UL 997, “Wind Resistance of Prepared Roof Covering Materials,” provides a similar test method and the same shingle wind-uplift resistance classifications.”

UL 790:

“These tests are required for the fire resistance performance of roof coverings exposed to simulated fire sources originating from the outside of a building. There are three classes of fire exposure: Class A roof coverings are effective against severe fire test exposures. Class B roof coverings are effective against moderate fire test exposures and Class C roof coverings are effective against light fire test exposures. All three classes are not expected to produce flying brands during fire testing. These can be conducted on a wood combustible deck (sheathing boards or plywood) or a noncombustible deck made of metal, concrete, or poured gypsum.”


Something else attractive to Americans making these “invisible solar roofs” even more attractive is that in many places it is actually illegal to put a solar panel on one’s roof, or almost anywhere! None of that reducing utility profits or making your roof stand out from your neighbours! Some of the localities are more entertaining in their reasoning.


One blogger’s (not very high) opinion on the Tesla roof tiles:

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