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  1. #1
    4K Club Member Marc's Avatar
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    Default New Solar system

    I am thinking in replacing my aging 1.5 KW Solar system for a bigger one, likely a 6 or 7 kw if there is enough room on the roof.

    Question for those in the know ...
    Salesman says "you use what you produce during the day and what you do not, goes to the grid"

    How does this actually work?
    I can't see the panels running my 3 phase welder during the day directly or the 32 amp spa if someone decides to jump in at the same time.
    Is the inverter actually smart enough to use whatever is available from the panels and top it up with the mains? Or is it just a matter of sending everything to the net and billing according to time of feed in?

    At the moment my switchboard is full with 5 meters, one per phase, one for solar and one for off peak. Will the new system reduce the number of meters in the box?
    Your reply is appreciated.
    Whenever you find yourself on the side of the majority, it is time to pause and reflect
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    Hi Marc,

    The solar system simply pumps as much power as it can produce in to your mains. This connection is usually ‘behind the meter’ which means that it is on the consumer side (your side) of the meter. This is also referred to as ‘net metering’.

    If you aren’t using any power, all the power will be delivered to the grid and your meter will record it as an export (and you’ll be paid a credit for that energy).

    If you are using power, but less than what the PV system is producing, the PV will in effect provide all your power needs. The ‘excess’ will still go to the grid.

    If you are using more power than the PV system can deliver, the PV power will be used ‘behind the meter’ and any shortfall in requirements will be imported from the grid.

    In effect, energy that you can use from the PV system ‘behind the meter’ is free energy (ignoring the capital costs of course).

    As you have a seperate meter for the solar, you may be on a ‘gross metering’ tariff. In this case, all the PV energy is exported, and all your power used is imported. You may want to check if (a) this is the case, and (b) is the new/upgrade net or gross? You’d have to do the sums to work out which is the best of you. Your power bill should indicate what tariff you are on. You should be able to look up that tariff on your supplier’s website and see if it is a gross or net arrangement.
    There is no middle ground between facts and fallacies - argumentum ad temperantiam

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    Community Moderator phild01's Avatar
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    Marc, you may want to confirm you are eligible for the govt rebates, you having an installation already. I was led to believe you only get one bite at the cherry, not sure!

  4. #4
    4K Club Member Marc's Avatar
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    Interesting so it actually uses what is produced directly.
    Yes, I am on a gross metering system. Worked Ok when the feed in tariff was high. After it run out 10 years later, I did not bother doing any changes.
    The systems are still subsidised to a certain extent, regardless of past subsidies. Prices have gone down a lot, a 6KW system costing me the same I paid for a 1.5kw many years ago ... may be 12 ... can't remember.
    Whenever you find yourself on the side of the majority, it is time to pause and reflect
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    Don't replace the system its a waste of your original investment. You should get another 10 years or more out of it. Worst case inverter fails which are not too expensive to replace.

    Put in a new system along side it. Its often best to go 50/50 on the East/West roof these days as well. Less peak production at midday but covers the house usage over the day better.

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    Regarding the thread title, thought for a moment you might have been an astronomer and made a discovery

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    2K Club Member chrisp's Avatar
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    Quote Originally Posted by Uncle Bob View Post
    Thought for a moment you might have been an astronomer and made a discovery.
    There is no middle ground between facts and fallacies - argumentum ad temperantiam

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    Without knowing what your solar access is (i.e space for panels with access to sunlight not shaded at different times of day), your usage patterns, and the import / export regime, and purchase / sell prices available to you, it is difficult to make meaningful suggestions.

    New solar PV panels are currently around $1.00 per watt, and good secondhand PV panels can be had for about $0.25 per watt. In my experience secondhand ten year old panels from Sharp still produce ~100% of rated output and will probably last a few more decades without major issues, however as reported by consumer advocates some panels from less reputable manufacturers are suffering severe loss of output well before 10 years. Likewise some inverters are rock solid and some fall like flies.

    A general principle more often than not overlooked is that generation capacity is only ½ of the equation. To get the greatest economic benefits you also need to consider the other ½ of the equation, which is the consumption side.
    Before you speak, ask yourself: Is it necessary, it is true, does it improve on the silence? - Baba

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    Community Moderator phild01's Avatar
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    Marc, if you press ahead with this I would be reluctant to go with the advertisers on TV. I would also not overclock the inverter. If you want a very good installer who knows his stuff and isn't pushy, let me know.

  10. #10
    4K Club Member Marc's Avatar
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    John, my panels are 180W and I have 9 of them. The inverter (fronius) carked it at 10 years and was replaced for a Solis. I looked yesterday and it was doing some 100W. The production showing on the invoice is pitiful, some 20 KW conceded in winter. In the good days it was doing 150kw per quarter

    From that, and pending an assessment from someone better qualified than me, it seems that keeping this system on the roof may be a waste of space.
    A friend of mine who installed the same system at the same time, has installed a 6kw system and left the old one there, however he has no trees around him and plenty of roof space. I have big trees on the west side and roof space is odd because the house has the original tile roof and a large second floor addition that is steel with steep fall.

    Phil, yes, I would like a recommendation for an installer. Thank you

    May be if I junk the panels I can sell the inverter (?). paid $1000 less than a year ago. I know it is a cheapy but is almost new.
    Top of the range siemens would have been just $500 more.
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    For info, here's a usage report from my 6kw system for yesterday. Green is production and Grey my usage.

    Attached Thumbnails Attached Thumbnails power.jpg  

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    Community Moderator phild01's Avatar
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    Quote Originally Posted by Marc View Post

    Phil, yes, I would like a recommendation for an installer. Thank you
    These reviews are honest and includes one from me
    https://www.solarquotes.com.au/insta...w/helioenergy/

  13. #13
    4K Club Member Marc's Avatar
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    Thank you Phil

    dmac ... that is a very clear graph for the solar nonchalant.
    So you produce way more during the day.
    Is the excess feed in tariff compensating for your usage outside production time?
    Whenever you find yourself on the side of the majority, it is time to pause and reflect
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    Hi Mac,

    @ 8 c/kwh it does not offset my night time usage but it certainly reduces the overall bill. We try and hammer it during the day as much as we can but you can see where the oven was turned on at about 6pm and the boss pushed the fast heat-up button.
    We would need a battery system to cover the dinner time peak but there's another chunk of money in that.

    We have 20 panels, so supplying a possible 7.2kw to the 6kw inverter. If I did it again I would have added a few more panels to broaden the spread of power over the day, so widen up that green graph.

    Dave.

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    Default New Solar system

    Our next solar system will likely use something like a Selectronics controller that ensures that the house needs are met and covered before either exporting to the grid or drawing from the grid. To that end, any power generated will first be used to create hot water and perhaps run air conditioning (if we install it) and whatever else after that. And the system will be designed and sized accordingly. Our average daily usage is less than 6 kwh...and we don't have off peak.

    We intend to use the grid as someone remote would use a back up generator. We don't intend to install a battery at this stage though provision will certainly be made for one...
    Joined RF in 2006...Resigned in 2020.

  16. #16
    4K Club Member Marc's Avatar
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    If I get rid of the old panels, I would have room for 14 panels on one roof and perhaps another 10 on the tiled roof. They would all face NE, if flat on the roof. Perhaps some could face N but on brackets. Not sure of rules on this one.
    Another thing I am uncertain about is our solar assisted hot water system. I installed it only because it cost me the same as an ordinary hot water system due to the crazy subsidies in Kevin times. However I am on off peak and before installation I used to spend $30 on off peak, and after installation it went down to $6.
    Today the off peak is $60. (?)
    I have no way to know if this contraption works as intended. I suppose that taking the heater off the roof can free up space for more panels.
    Whenever you find yourself on the side of the majority, it is time to pause and reflect
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    Resigned SilentButDeadly's Avatar
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    Default New Solar system

    NE facing panels are not ideal...N facing and properly angled for autumn/winter sun angle at your latitude would be better.

    Sounds like you have electric boasted thermosiphon solar hot water. They are basic, effective and hard to kill. The off peak cost changes probably reflect more on the rapacious nature of your electricity supplier than the hws capacity to make hot water
    Joined RF in 2006...Resigned in 2020.

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    Community Moderator phild01's Avatar
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    I have read NE and NW is best, NW being better, but not directly north.

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    Is Marc thinking of buying an electric car with the big solar expansion?

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    Quote Originally Posted by SilentButDeadly View Post
    Our next solar system will likely use something like a Selectronics controller .
    The Fronius inverters are a good option. There is a relay output that can be programed to kick on when export reaches a certain point. Smart people use it for the hws booster or other similar items.

    North used to be best when you were paid the high rebates. These days on most power contracts you are better having a array aligned more east/west. Slightly less production over the day but covers the house usage better.

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    Sorry I've been away and hadn't responded to your question, Marc. I read you are grid connected and I gather your objective is to maximise return, or minimise your electricity account, which is actually the same thing for a grid interactive system like yours. For a simple system where your are paid less per kWh for exports than your electricity costs per kWh for usage, this this means maximising the total generation during the four seasons and where possible shifting your own consumption to when the sun is shining. Because there are longer hours of sunlight in summer, the greatest annual total generation is achieved by optimising for the summer's sun. That means (unless there are obstructions such as trees) panels that are fixed in position should face close to north at approximately the angle of your latitude. Panels facing significantly away from north will produce considerably less electrical energy over each day, irrespective of time of year.

    Your space is somewhat limited for 6-7kWs of panels, so it would be best to replace your existing panels. Panels have crept up in efficiency and a panel now is typically ~300W, and not necessarily the same size as your old panels. Mixing panels of different physical size and outputs is not optimal for grid interactive systems like your IMHO, because there is likely to be more roof space wasted and additional inverter costs to accommodate sections of panels of different specifications.

    PV systems operate in 'strings' of panels, a string being from one to ten panels in series, and usually somewhere between these limits. For each string the voltage is the sum of all the panels in the string and the current runs through each panel in turn. The strings are typically 'paralleled' at the inverter so the currents from each string add together. One thing to understand is that if just one panel in a string is shaded, then all panels in that string will have reduced output. On the other hand, a system that has all strings being just one panel mean large currents are involved and cable losses are high. Different inverters are designed around an optimal input voltage range which also determines the limits (both minimum and maximum) of the number of panels in each string for that inverter.

    In my experience not enough effort is given by designers and installers to maximise the system output by optimising the number and layout of panels in the strings. In my system (which due to the orientation of the house faces NE) the original installation had 4 strings of 4 panels. By changing this to 8 strings of 2 panels I have increased the output by as much as 50% on many days. This is because there is some early morning shade that sweeps from the whole array back to one end of the array, so making sure as few panels as possible are affected makes a significant difference to electricity produced, and also because 4 panels in a string was voltage limiting at the electronics which were also slightly below peak conversion efficiency at the higher voltage of four panels added together. The voltage of two panel strings is close to optimal conversion efficiency in my case, but this is not necessarily true for other equipment.

    Changing each string to two panels halves the voltage and doubles the current, but in my case prevents considerable loss of output from partial shading, prevents the electronics voltage limiting and moves system operation into a more efficient region. Changing the strings has implications for cabling and the ratings of circuit protection the optimisation should be done before design, not after installation.

    I am off grid, so maximising energy in winter when we need it most more important than maximising annual total output. That still means panels facing north, but tilted up to be perpendicular to the winter sun. This gives less potential electrical energy over the year, but we can't use the extra summer energy anyway. When it isn't being used the panels just don't produce as much electrical current. Instead the panels get hotter because more of the Sun's energy is converted to heat and less to electricity. Even so the panels do shade the roof and help keep the house cool inside over summer heatwaves, the roofing iron being about 40 degrees cooler under the panels than in direct sun.
    Before you speak, ask yourself: Is it necessary, it is true, does it improve on the silence? - Baba

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    Quote Originally Posted by Uncle Bob View Post
    Thought for a moment you might have been an astronomer and made a discovery.
    If I discovered a solar system, it would definitely have a Pluto

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    4K Club Member Marc's Avatar
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    Quote Originally Posted by Bros View Post
    Is Marc thinking of buying an electric car with the big solar expansion?
    Nee, reverse empty nester, electricity bill doubled
    Whenever you find yourself on the side of the majority, it is time to pause and reflect
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    4K Club Member Marc's Avatar
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    John ... interesting about the two string panels thingy. Will ask the installer when he comes. I do have shade from one tree that sweeps across the line up of panels.
    In your case you should have all your panels away from the house on a rotating and tilting platform. Rather easy to make if you have room. Not particularly aesthetic though.
    Whenever you find yourself on the side of the majority, it is time to pause and reflect
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    Nowadays extra panels are a much cheaper option than trackers. Plus more panels perform better than a tracker on cloudy days when the direction a panels face doesn't make much difference because the irradiance is diffuse. Also as a mounting systems a roof is generally free, whereas a ground frame has to be engineered and built, plus it needs to be weeded.

    Good luck convincing your installer about the importance of maximising system performance by optimising strings. I regularly get asked to check other people's PV system performance. Not many designers seem to understand string theory, pardon the pun. There are conflicting design requirements for any PV system and the obvious compromises don't necessarily work out to be the best IME.
    Before you speak, ask yourself: Is it necessary, it is true, does it improve on the silence? - Baba

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    Quote Originally Posted by John2b View Post
    Not many designers seem to understand string theory, pardon the pun
    I take it the less panels on a string and more strings is best?

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    Quote Originally Posted by Uncle Bob View Post
    I take it the less panels on a string and more strings is best?
    Yes, especially with shaded panels.

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    Quote Originally Posted by Uncle Bob View Post
    I take it the less panels on a string and more strings is best?
    It depends on the specification of the panels and the specification of the charge controller or grid inverter. Less panels in a string means more current for the same total power, more copper in the cables to minimise losses and more cables so as not to exceed the 30A rating of the MC4 connectors. On the other hand, inverters tend to be more efficient at higher voltages, as long as the rated maximum voltage is not exceeded. Many manufacturers have a "string optimiser" program or app to work out the optimum number of panels in each string and number of strings for a given combination of panels and inverter. As Phil said, smaller strings of panels will loose less output when partially shaded, and also it is also important that panels in the same string are positioned so they tend to get shaded at the same time, rather than having shaded panels spread across multiple strings.
    Before you speak, ask yourself: Is it necessary, it is true, does it improve on the silence? - Baba

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    ...John's on the money.

    For more info go to https://www.solarquotes.com.au/
    These guys have been around for 12+ years and have some great info.

    Submitted a request for 3 quotes and talking to a guy from one company today, (maybe it was you John ) was saying similar content. Generally oversize the system by a little (not too much as its longer to get payback for the system) so as to maximise the spring/autumn yields, improved winter yields and the summer yield will take care of itself. He was saying on order of preference facing N, NW, NE.

  30. #30
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    Quote Originally Posted by John2b View Post
    Without knowing what your solar access is (i.e space for panels with access to sunlight not shaded at different times of day), your usage patterns, and the import / export regime, and purchase / sell prices available to you, it is difficult to make meaningful suggestions.

    New solar PV panels are currently around $1.00 per watt, and good secondhand PV panels can be had for about $0.25 per watt. In my experience secondhand ten year old panels from Sharp still produce ~100% of rated output and will probably last a few more decades without major issues, however as reported by consumer advocates some panels from less reputable manufacturers are suffering severe loss of output well before 10 years. Likewise some inverters are rock solid and some fall like flies.

    A general principle more often than not overlooked is that generation capacity is only ½ of the equation. To get the greatest economic benefits you also need to consider the other ½ of the equation, which is the consumption side.
    They are a lot cheaper than that now, I have had quotes from various large suppliers, 6.6KW installed all around $3600, some also had a $500 one off incentive, there was some down around $2600.
    Lots had no upfront fees, interest free payments over 21months of $40 - 45 / week.

    They had 5Kw Inverters which is ok, but the system is only 6.6Kw so it's fine, all had 10 / 12 year warranty on installation and inverter
    Mieux vaut prévenir que guérir

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    Metrix, those Sharp panels you referred to; were they made in Japan and are they still made in Japan?

    Merci.

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    Quote Originally Posted by METRIX View Post
    They are a lot cheaper than that now, I have had quotes from various large suppliers, 6.6KW installed all around $3600, some also had a $500 one off incentive, there was some down around $2600.
    Lots had no upfront fees, interest free payments over 21months of $40 - 45 / week.

    They had 5Kw Inverters which is ok, but the system is only 6.6Kw so it's fine, all had 10 / 12 year warranty on installation and inverter
    I saw the ad for $2600 but the small print excluded the installed meter costs.
    I would also be wary of the ones promoted on TV being quite a number of disgruntled purchasers online.
    Also with inverters limited in NSW to 5kW, i think the inverters would have a short life being overclocked especially when installed exposed to the sun. My inverter is ideally located under the house and my panels are just under 5kW and the inverter gets damn hot running flat out.

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    Quote Originally Posted by fredgassit View Post
    Metrix, those Sharp panels you referred to; were they made in Japan and are they still made in Japan?

    Merci.
    I doubt it, Chinese would be the panels being offered, here is a good article on who manufactures them, most panels in the world come from China.
    Don't know if Japan even makes panels for anything outside their local market, they would be to expensive.

    https://news.energysage.com/best-sol...ivint%20Solar.

    I can't put solar on my house effectively as there are too many big trees around the house so the system is useless.

    I still don't understand why in the almighty USA solar systems are SOOOO expensive, considering our lower AU$ compared to the US$ they are basically giving them away here.



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    Thanks Metrix!

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    Quote Originally Posted by phild01 View Post
    Also with inverters limited in NSW to 5kW, i think the inverters would have a short life being overclocked especially when installed exposed to the sun.
    Its not a computer and overclocking is a totally inaccurate description.

    The MPPT electronics in the inverter sweeps through the usable volts range to find the point of maximum current/power from the solar panels. If at say 500v it has all the power it needs it does not allow the voltage to go higher and holds there. As an example the Fronius I have works between 240 - 800 V.
    While there is limits on what the electronics is capable of controlling there is no "extra" heat from having excess panels and most inverters spec a significantly higher capacity for the solar array than AC output. ie Fronius 5000w AC and 7500w DC.

    Obviously there is quality differences in design and the cheaper units are often not suited via temp ratings for use in Australia's summer at the rated maximum output.

    Also most people with a clued in installer are splitting the arrays East/West or NE/NW these days so while you never get the peak output at midday of unusable power it does cover the house usage better through out the day.

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    I'm looking at putting in a $9K 10KW system consisting of 31 × 330W Seraphim Blade panels with Optimisers, and a SolarEdge SE10000H 10KW inverter.
    I can only export 5KWH though so an electric water heater will be next up.

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    Quote Originally Posted by doovalacky View Post
    Its not a computer and overclocking is a totally inaccurate description...
    Correct, and so is the rest of your post, thanks. I've got four arrays of panels facing NE, N, NW and SW. It might seem counterintuitive but on overcast days all four arrays produce electricity equally efficiently because the light source is diffuse. The NW array is dual purpose because shades the roof from late afternoon sun in summer, keeping the house cool on extreme weather days.
    Before you speak, ask yourself: Is it necessary, it is true, does it improve on the silence? - Baba

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    Quote Originally Posted by Uncle Bob View Post
    I'm looking at putting in a $9K 10KW system consisting of 31 × 330W Seraphim Blade panels with Optimisers, and a SolarEdge SE10000H 10KW inverter.
    I can only export 5KWH though so an electric water heater will be next up.
    Why so big as you get next to nothing on feed in rate

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    Quote Originally Posted by doovalacky View Post
    Its not a computer and overclocking is a totally inaccurate description.
    Whatever, just generally saying the oversized system's inverter is working harder. The array limit for a 5kW inverter is 6.6kW, I guess because it is assumed in Australia, the 5kW won't be exceeded so a limit for not exceeding 133% in panels, correct me if wrong. But I know my Sungrow system sometimes, but rarely, touches it's limit as does another SMA system I know of.

  40. #40
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    Quote Originally Posted by Bros View Post
    Why so big as you get next to nothing on feed in rate
    Hi Bros,
    My reckoning is that with having more panel output I'll have a longer time period during the day at the max 5KW.
    Am I incorrect in this assumption? I new to this this but have read that more panel output than inverter capacity is now a good thing since panels are cheaper these days.

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    Go for it UB. I have 8.12kW of panels on an 8.2kW inverter, export limited to 5kW, but with spa and pool to keep running I'm rarely export limited. 10kW of panels would be better use of the inverter on below average days, but, yeah, money, and no regrets

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    Slow but rough Uncle Bob's Avatar
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    I'm evening thinking of getting upgraded to 3 phase for 15KW export

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    Quote Originally Posted by Uncle Bob View Post
    I'm looking at putting in a $9K 10KW system consisting of 31 × 330W Seraphim Blade panels with Optimisers, and a SolarEdge SE10000H 10KW inverter.
    I can only export 5KWH though so an electric water heater will be next up.
    Would solar hot water work out cheaper than solar heating with panels.

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    Slow but rough Uncle Bob's Avatar
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    Quote Originally Posted by phild01 View Post
    Would solar hot water work out cheaper than solar heating with panels.
    I haven't looked too deeply into yet. But I was thinking solar with electric boost.

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    I would stick with off-peak hot water if you have it, far cheaper than a solar installation especially using optimisers.

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    Slow but rough Uncle Bob's Avatar
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    Currently have gas HW. Going to slowly switch everything over to electric.

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    Quote Originally Posted by Uncle Bob View Post
    Hi Bros,
    My reckoning is that with having more panel output I'll have a longer time period during the day at the max 5KW.
    Am I incorrect in this assumption? I new to this this but have read that more panel output than inverter capacity is now a good thing since panels are cheaper these days.
    You should start to do your sums now not just guess it. I have a 3 kw system and the panels are on both side of the roof to catch more solar and it is more than enough. Doing sums on the feed in tariff is an exercise in losing money as the system doesn't want rooftop solar and the feed in tariff is priced accordingly. As an example for the last month bill I fed in 284 Kwh and I generated about 435 Kwh. I have left my AC which I use in summer on tarrif 33 as I only us it during the night the main AC in the lounge would only run about a dozen times during summer. The HW is on Tariff 31 but the cost of changing it over to use the excess solar wasn't worth it.

    One thing I could do is change our laundry and drier to Tarrif 11 and make sure my wife washed on days when the solar is exporting but the cost of asking my wife to change her was days was to expensive to me to bear.

    So big is not better.

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    Slow but rough Uncle Bob's Avatar
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    I've let the experts crunch the numbers. Going on my power bill/consumption they recommended a 6.6KW and a 10KW system, with the 10KW having a faster pay back.

    If anyone else wants to have a crack at the calculations please feel free to do so.
    Our house averages 25KWH per day consumption, at $0.23 KWH (`$170/month). Rebate is $0.15 /KWH. There's no off peak power on my plan.

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    Quote Originally Posted by Uncle Bob View Post
    I'm looking at putting in a $9K 10KW system consisting of 31 × 330W Seraphim Blade panels with Optimisers, and a SolarEdge SE10000H 10KW inverter.
    I can only export 5KWH though so an electric water heater will be next up.
    If you don't have shading issues I wold not waste money on the optimisers. Adds a over a $1000 to the cost for little benefit.

    Ask your installer about a option like a Fronius with export energy monitor and the relay wired to an electric booster.
    Basically it can be set up to kick in the electric booster when ever you are exporting a set amount of power optimizing your power usage. You then just have a timer in switchboard that also starts the booster at say 5pm to get the temp up if has not made it during day.
    My timer runs for an hour but most days is not needed.

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    Quote Originally Posted by doovalacky View Post
    If you don't have shading issues I wold not waste money on the optimisers. Adds a over a $1000 to the cost for little benefit.
    Hi doovalacky, thanks for your response. I questioned the solar guy about this and he agreed with you, but he said the pros outweight the cons by using optimisers. The biggest benefit was that you're not using strings so panel placement can be optimised, other benefits are, shading only affects the panels that are shaded. You can use any brand of panel so they can be mixed. You can also add more panels (with optimisers) at any time.

    He reckoned the while the Fronius are inverters good, the SolarEdge inverters are the bees knees and the company has the best continued investment and ongoing development.

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