Jump to content


This week I went solar :)

How cool new technology is... Micro-inverters are cool!

  • Please log in to reply
157 replies to this topic

#1 g__day



  • Hero
  • 7,902 posts

Posted 03 March 2015 - 11:15 PM

About two weeks ago my eldest son asked a simple question "Dad - why don't we go solar?".  Talk about an idea whose time had come.  We weren't financed nicely when the solar wave first broke - and you could spend $24K for a 3kilo Watt system that guaranteed your a 0.66 cents feed in from the grid for every kilowatt hour (kWh) produced.  It was an idea that has been at the back of my mind for some time now - but I had done no research on it.  But having three teenagers our annual electricity bill is around $3,600.  So I thought why not indeed?


I googled a bit and found the idiots guide to and how to get decent quotes and read Whirlpool's Green forum and came to a very interesting realisation - now's a great time.  My research basically showed electricity costs have pretty much quintupled whist solar cost had gone down by a factor of three, whilst capability and energy management systems had pretty much arrived.  This is the short story of how in two weeks we sized, selected and implemented a 4.94kW system that is monitors energy provision and you can browse the web any time to see how your house, or thousands of people all over the world are producing in real time.


The biggest learnings I got where


  1. There are a handful of tier one solar cells (Trina from China and Q-Cell from Germany) seem to be the best
  2. Inverter selection is critical - you feed all the solar panels arranged in identical rows (called strings) into one big, unintelligent inverter that will die in around 8 years or you go with intelligent, programmable micro-inverters that allow amazing flexibility but cost more
  3. You plan your system to cover your average Summer day time load (for me around 30 kWh)
  4. You consider a system that you can add battery storage to to better manage peak versus average day time load
  5. You reality check that you can consume at least 70% of the energy you produce rather than over produce and feed it to the grid for a pittance of a pay back rate.
  6. You select an energy monitor that displays not only what you produce but what you consume
  7. You seek to implement a solution with a four to six year payback over a likely twenty five year life (meaning it should save you tens of thousands of dollars)!

The first week was spend modelling how large a system we wanted, and coming to the realisation it should offset our minute by minute day time electricity consumption.  So after reviewing a few quarters of energy bills I was able to reasonably determine how much we use each day.  Next it was understand the tariff system - I am with AGL so it costs me 55 cents for peak power, 23 cents for shoulder and 11 cents for off peak.  I can earn a measly 8 cents for power we feed into the grid - even at peak times! This means you size your average hourly peak load, then double it to allow for semi-sunny days.


I did all this and arrived at 5 kW - which every quote I got confirmed my analysis.  But the biggest realisation on gear came from just how impressive a micro-inverter solution is and how intelligent they are, and how future ready they turn out to be.  A micro inverter is simple a small programmable inverter that sits at the back of each solar cells and is constantly talking to a gateway controller and from there to the web.  Enphase have a huge lead in this market and a stellar reputation.  It brought my costs up from around $7,500 to $8,700 - but it dramatically increases the life time value of my system.  Micro inverters have a few very cool advantages:


  1. There mean time between failure is 129 years
  2. If a micro fails the rest of the system performs unaffected
  3. If a cell with a micro under performs - the rest of the array is unaffected.  With string / central inverters if a single cell in a row under performs the whole row performs down to the level of the worst cell (shading one cell drops the whole string by this amount)
  4. If a micro performs out of specs it will generate alerts in real time - and your energy installer will notify you before you realise an issue is even begining
  5. Micro designs allow for any size, number and random type of cells to be placed anywhere on your roof
  6. Micro's are constantly tracked and reported for all systems installed world wide - they individually report to a gateway controller and you can use any smart device with a browser to see you energy creation history in real time.
  7. Micros only run low voltage (30 - 38 volt) current across your roof to the fuse box.
  8. Micros allow for later addition of battery storage (in pilot now and coming out later this year).

So I got three quotes for a 19 Trina cell (260W) M250 Micro-inverter second story roof install on a tile roof, with 7 cells placed facing North and 12 cells facing West.  North facing cells produce more energy during the day, West facing cells produce more energy at the time of the day when our consumption is at its maximum.  Solaray eventually beat Nicholls with a cheaper price and a much faster install.  Roof brackets, meter change over and internal wiring went up on Tuesday last week (then at 2pm the skies poured down).  The team came back and installed the micro inverters and solar cells on Friday afternoon and installed the gateway controller in the fuse box.  Finally on Saturday one of their head engineers came in a also installed a Wattson energy meter (tracking both consumption and provision of energy) and then told the gateway to switch everything on voila we were producing!  By Tuesday my systems exact configuration was loaded into their world wide web database and I could see everything it was doing.


The Wattson really helped me understand energy hogs.  The big ones we switch out of hours to off peak when we can (pool pump - 1.2 kW, clothes dryer 1-2 kw, clothes washer 0.5 - 1.5 kw). The other main energy guzzlers running during the day are a big ducted air conditioner - 3.5 kw and a big electric oven 2kw.  The Wattson sits next to our kettle in the kitchen downstairs and shows us moment to moment what we are drawing or feeding into the grid (and many other things).


Anyway if you'd like to see what we produce its here: https://enlighten.en...tems/LbBY574110


This shows how much energy we produce - by month, day or 15 minute intervals.  The System in a fully Sunny day should produce North of 30kWh a day - but so far we have had three half days were its done between 18 to 22 kWh.  At present we have created created 76.7kWh, of which 17 where exported to the Grid and the rest we consumed for our selves.  If we keep that rate up the gear will pay for itself in just over four years of its 25+ year life.


Hope this is very useful information to share.  I ponder how many other folk have gone solar and has it deliver, failed or exceeded your expectations.


Later this year I will consider sizing additional battery storage and see if its economical to store what we over produce and feed back in when our peak consumption - say 6 kWh for a few hours - exceeds what this system can do at peak 4kWh.  So if I desire a 5 - 15 kWh storage solution is this economically sensible or should I just buy excess energy from the grid.  All up I hope this solution will at least hlaf my bills going forward - if not better if I can use it wisely!





Talent + Integrity = Atomic!

#2 Rybags



  • Super Hero
  • 35,751 posts

Posted 03 March 2015 - 11:57 PM

I thought they were still paying like 40 cents per kwH you fed in.


Bit of a ripoff getting paid 8 cents despite paying 55 in peak hour.


Things are different here (for now) - ACTEW/AGL does deals in advance for the ACT so we have among the "best" prices in Aus... I'd prefer to say "smallest ripoff".  Peak usage is 16.64 cents, not sure about off-peak as don't have anything using it any more, something like 2/3rds peak.

#3 g__day



  • Hero
  • 7,902 posts

Posted 04 March 2015 - 01:54 AM

You currently get a solar rebate on gear purchased - so my system retails for $12.5K but rebates from the Government bring this down to $8700.


In NSW only 7 retailers offer anything - the minimum isn't regulated.  http://www.solarchoi...ff/?fitpage#NSW


Click Energy offers the most at 10 cents a kWh and AGL and Diamond Energy come equal second at 8 cents.  The lowest rebating pays 5 cents - the rest pay nothing!  So even though the grid is overly expensive to cater for peak - and peak is premium priced to us - supply energy to the grid during peak earns us less than their off peak rate.  That I think is something the Government could regulate - saying their should be no more than a 2 cents difference between buy and sell rates!


Also I pay $77 a quarter connection fees for AGL to keep up their grid.  If I am a net exporter to them - they should reverse that payment to me and pay for my gear by that logic.


What you can see is a sea change happening as the price of solar generation longer term is tipped to fall to 2 cents a kWh.  At present it costs under 20 cents per kWh when you do the sums of total lifetime expected kWh produced divided by purchase cost.

Talent + Integrity = Atomic!

#4 TheFrunj



  • Atomican
  • 14,277 posts
  • Location:Atomic Labs

Posted 04 March 2015 - 10:24 AM

Interesting post, thanks for taking the time to write it up / repost here(?).


When I looked into off-grid power storage a year ago there wasn't anything that was more cost-effective than simply using grid power. Especially considering the charge/discharge life of battery storage, it wasn't too appealing. Perhaps it's changed but I doubt it.


I've read about off-peak battery storage to save money at peak times, or using excess power to freeze water to replace air conditioning at night, but these all need a bit of work to be practical.

"TheFrunj doesn't guess, when he forms words with his lips, the world will Warp and change to do his bidding." - Shikimaru No longer writing for Atomic :( http://forums.atomic...showtopic=49899

#5 Mac Dude

Mac Dude


  • Super Hero
  • 36,561 posts
  • Location:Melbourne

Posted 04 March 2015 - 10:34 AM

We went live at the end of last year.  I basically went through a similar eval process you did.  When I looked at it years ago the feed in tariff was tempting, but the outlay costs were huge.


Over a few months I started the solar conversation with a guy who was advising on solar at the school where the missus works.  We went through the numbers again and again then bit the bullet.  The main reasons for going ahead this time was the dramatic drop in the cost of solar and the ability to use micro-inverters to overcome some shading issues we have.


We are happy with the result so far, but I'm very interested in the production over winter.


A few weeks ago I had a chat with our power distributor and there is no way for me to get a 'near time' feed of our energy consumption which I would have liked.  At the moment I get the data from the solar gateway online and pump it automatically into http://pvoutput.org/ which is a useful platform for combining all your energy info and forecasting usage/cost etc.


I do love checking what we are producing :)



Karl Kruszelnicki - No, I’m fully prepared to believe in the “Church of God the Utterly Indifferent who sets the universe going and says you’re on your own kids.

#6 tastywheat



  • Atomican
  • 1,842 posts

Posted 04 March 2015 - 11:07 AM

POTM (if that still happens?)


Pretty awesome to see that renewables have become not only practical, but profitable over a long enough period.  We still need to refine our energy storage technology, and there's going to be an interesting dilemma when the number of people going off grid start to make it significantly more expensive for those that can't afford the upfront costs, but the future is looking pretty damn cool.

#7 Master_Scythe



  • Hero
  • 20,552 posts
  • Location:QLD

Posted 04 March 2015 - 12:59 PM

Ive long considered how I want to approach solar.

I don't like the 'changing rebates' or the "Dont touch that, its on the grid" rules.


What I then thought to myself was "Can I go off grid?" To which I quickly realised, no; I can't. I use too much power.

Then I thought, "Can I go more efficient?" and realised, HELL YES I can.


I'm in the market for my own place right now; and I'll be doing one simple conversion.

My lighting circuit (which in all houses is its own circuit, by law), will be connected to an off grid small, simple, battery bank.

Which will be charged by simple solar panels, at 14v.

And I'll be using 12v LED lighting throughout.


Its probably the one power draw item I have to use, and have no pleasure in using.


Computer, TV, cooking, all things I enjoy; Light is simply a necessity that I can avoid paying for.


Depending how the law works once that circuit is off grid, I might even get the sparkie to run a few 12v sockets throughout the house to use things (through a car adaptor) like USB fans, charge my phones, and run my LED desk lamp.


I never do things "The norm" way :P

Wherever you go in life, watch out for Scythe, the tackling IT support guy.

"I don't care what race you are, not one f*cking bit, if you want to be seen as a good people, you go in there and you f*ck up the people who (unofficially) represent you in a negative light!"

#8 Director



  • Hero
  • 40,460 posts

Posted 04 March 2015 - 01:31 PM

Always thought they were great idea....now if I only owned a roof....


You might also be interested in this:



"The most powerful tool in the hand of the opressor is the mind of the opressed."-- Steve Biko

Those Who Dance Are Considered Insane by Those Who Can’t Hear the Music.

#9 g__day



  • Hero
  • 7,902 posts

Posted 05 March 2015 - 12:26 PM

Great system Mac Dude!


I just did some back of the envelope calculations regarding the possibly economics of battery storage solutions.


For my system day 4 (partly sunny weather) 110 kWh of energy have been produced and 50 kWh of these went to the grid (basically paying for Off peak use – not peak or shoulder use). Let's say I do a crude weighted average and say average daytime energy costs me 40 cents per kWh. Then I might guess 70 kWh a week go to the grid rather than feed my day time usage without any energy storage option (so I have an opportunity loss of $28 a week = .4 * 70).


So say on average I send 10 kWh a day to the grid. Therefore a 10 kWh battery system would allow me to capture that power and use it against peak or shoulder times (rather than generate 8 cents a kWh for it). Assume that this system isn't allow to be re-charged from the grid... Then each day the system could at best pay for peak power at 55 cents a kWh (less meaning no grid feed at 8 cents a kWh) meaning I am 47 cents a kWh better off – at best. Big IF – if I could do that 365 days a year – well that's a saving of $4.70 a day times 365 days = $1,710 a year. Over ten years a payback increase of $17, 108. So given all those things work right, what would the cost of a 10 kWh system possibly be? Well Enphase are producing a 1.2 kWh module so to get 10 kWh you could have 8 to give you 9.6 kWh with a ten year life. So that adjusts the savings down to $0.47 * 9.6 * 365 * 10 = $16,468.80. Divide this by 8 and you get $2,058.6.


So my reasoning stand that if you could optimally consume every spare kWh you produced – you might break even from a battery storage solution provided the storage costs no more than $2,058.6 per 1.2 kWh battery...


So in real world terms you would like double that savings to allow for sub-optimal conditions – say a round $1,000 per battery gives you a neutral rate of return in real world conditions. To get a 20% rate of return you would want these batteries to retail installed at say $800.

So at launch they may be anywhere from $800 to $2,000 per 1.2 kWh (total guess) but only at a cost to you of $800 at current prices would they be economically appealing.


Does that accounting treatment sound correct to people? I basically presume I charge batteries during the day and use them from say 4pm to run ovens and or air conditioning for 2 to 4 hours to supplement a maybe 1+ kWh solar feed in. So a 4 (550W) * 2 set up (2 banks in parallel of 4 in series batteries) would give 4 * 550 W = 2.2 kWh boost to the solar for (1.2 kWh / 550W *2) = 4.36 hours. If I produce but don't consume this power, say we eat out or I bbq or cook with gas stove top rather than electric oven, and I don't use my ducted air condition to cool or heat the house) then the savings are lost so storage is less beneficial to me!

Talent + Integrity = Atomic!

#10 Mac Dude

Mac Dude


  • Super Hero
  • 36,561 posts
  • Location:Melbourne

Posted 05 March 2015 - 01:30 PM

The biggest question mark I have over my quick reading of the above is how much you're pumping into the grid. To compare how I'm going versus how I should be going I used one of the solar calculators that takes your location, type of system, etc into account.

This is vital. For example, being in Melbourne the generation estimate for June is 30% of what I produced in Jan. Now I've taken a pretty conservative approach to my estimates so maybe June won't be so bad. On the consumption side, do you consume more in winter than summer? If so, then you're generating less but using more and this will have a massive impact on what your pumping into the grid or your battery.

If you're interested in putting together your own estimate check out http://pvwatts.nrel.gov/
Karl Kruszelnicki - No, I’m fully prepared to believe in the “Church of God the Utterly Indifferent who sets the universe going and says you’re on your own kids.

#11 g__day



  • Hero
  • 7,902 posts

Posted 06 March 2015 - 10:45 AM

Great questions and observations.  It's too early to tell - but being informed of what you are doing with your solar generation allows you to make a decision where you direct your energy - if someone is at home!  Without batteries my system will over produce during the day time if no one is home to consume the energy.  Yesterday was cloudy around midday but the system still generated 27 kWh.  Thanks to cooking a lamb roast in the afternoon so of the free energy was used and peak was free.  Since last Sat lunch time we have produced 132 kWh - of this and consumed 69 kWh and fed the Grid 63 kWh.  The way the maths falls out of this is our system has made us $29 in six days.  If that trend continued it would save us around $440 a quarter or $1.7K per year giving a payback of 5 years. 


But it's way too early to predict financial outcomes from this little data.  The system has the potential to save us significantly - it's now up to us on how well we can use it!

Talent + Integrity = Atomic!

#12 Waltish



  • Hero
  • 14,236 posts
  • Location:Cooya Beach FNQ

Posted 06 March 2015 - 12:05 PM

This is a great thread , I don't own a house, reading about current solar solutions, and in particular your well planned and executed move into Solar, does show solar on the home to be a viable and economically beneficial  product.


Well written g__day  :)

? After All This Time ?

.....<--{ Always }-->


...PSN ID = waltzz22

#13 Mac Dude

Mac Dude


  • Super Hero
  • 36,561 posts
  • Location:Melbourne

Posted 06 March 2015 - 01:02 PM

the thing i had to get my head around g_day was the switch in mindset from 'make a profit' to 'save money'.

When the feed-in tariffs plummeted in Vic, I basically gave up on the idea. Only when prompted did I start to do the sums again, and 3 factors had changed - the introduction of micro-inverters, the drop in outlay and the increase in power costs. These 3 factors more than made up for the tariff loss.

We have a power hungry house thanks in part to the 3-phase aircon and the electric spa. The solar has insulated us from the continuing power cost increases while allowing us to use the aircon and spa without worrying about the cost.

Once I started to think about the solar just being an incremental cost of these items, it made even more sense...

I'm very interested in grid connected storage, but from my rudimentary research it seems a bit early.

Edited by Mac Dude, 06 March 2015 - 01:03 PM.

Karl Kruszelnicki - No, I’m fully prepared to believe in the “Church of God the Utterly Indifferent who sets the universe going and says you’re on your own kids.

#14 stadl



  • Super Hero
  • 9,056 posts

Posted 06 March 2015 - 05:17 PM

the thing i had to get my head around g_day was the switch in mindset from 'make a profit' to 'save money'.


That is a big part of the variable use-case for different people on different feed in tariffs.


I got my 5kW solar system 15 months ago, and Export most of my power - currently at 24c/kWh but in a year that will drop to around 7c/kWh. I buy power at around 33-39c/kWh depending on quarterly use, but it doesn't change peak/offpeak

So best thing is for me to use my own power and avoid importing, and once the FIT drops It will be more so. So my use-case, is run appliances like washing machines, dishwashers etc during the day while the sun is shining.

I have to export 2kWh during the day in order to offset buying 1kWh at night, at the moment I easily do that, and end up with a net credit of $50-250 per quarter depending on season even after service charges - but once the FIT changes, it will be 5:1, and that will be touch and go.


A friend installed about 5-6 years ago, paid megabucks to install, but they're on 66c FIT, It's better for them to export than consume their power, so unlike me, they run their appliances at night.



I'm very interested in grid connected storage, but from my rudimentary research it seems a bit early.


Once full 'time of use' metering is installed, it will quickly become popular with households with heavy shoulder demand in the mornings and evenings.

Doesn't have to be a big battery then, just able to store generation from the previous period to cover the shoulder.

The common intelligent demand/charger scenario is envisaged as:

- During the day at peak prices, solar system exceeds all your needs, and has enough to throw maybe 5-10kWh into storage, but depending on the user, may be workable with 2-3kW

- In the evening as prices drop a little, but not as fast as solar output - and this is typically family peak consumption as people return from work, cook dinner etc. The storage system supplements solar generation, to minimise import, Battery exhausted in late evening, but hopefully, by the time you  are importing much, it's the cheap off peak.

- over night at the cheapest price, the battery charges from grid,

- Morning wake up demand is back on shoulder prices, so battery delivers demand until the solar generation takes over


That sort of profile doesn't require huge capacity, and also can cost effectively tolerate leakage/decay, as the cycle time is < 12 hours., That can make non-battery technologies viable.

A device so simple that it took a mind as brilliant as mine to create it! So brilliant, in fact, that simply by harnessing the power of one live frog, it... it... uhh... <poke> <poke> ... World domination has encountered a momentary setback. Talk amongst yourselves.

#15 g__day



  • Hero
  • 7,902 posts

Posted 06 March 2015 - 06:07 PM

It will be very interesting to see how energy retails lobby around energy storage solutions - which effectively allow you to shift demand and usage from time of creation to time of need.  I would guess they would hate selling me off peak energy that I could use during the day - and will pressure installer / regulators to not allow any energy storage systems to be topped up from off peak energy they themselves supply.


This is really gouge pricing - they buy at the rate they sell.  If one has a fully electric car then you bet you will be charging off peak at night and using it during the day.  So its an area where technology I would say is in front of the commercial law governing its use or constraints on its use. 

Talent + Integrity = Atomic!

#16 scruffy1



  • Hero
  • 5,624 posts
  • Location:near the beach

Posted 06 March 2015 - 09:26 PM

that's really interesting stuff


the most surprising thing i learnt was how much power i don't use compared to many of you


a household of 2 adults, one adult offspring and a nearly teenager, all with a desktop and laptop of sorts, but gas cooking and heating (soon to be induction and electric oven, and maybe a reverse cycle aircon - none presently )

obsessive bill recording since 1993 (!)  shows gas use being stable and electricity going up some, but we only use a megawatt (or less) a quarter, and maybe 1000megajoules a quarter averaged out


last year that's $1.05k in gas and $1.2k in electricity all up


hmmmm.... $9k is just on 4 years to pay off if we go total electric and could use it all


but my guess is a few years on with tariffs exponential, it will pay itself off in less for sure... i'll start a trust fund for that, and look forward to some calculations once the new (electric) kitchen gets in



thanks for such food for thought :)


#17 AccessDenied



  • Hero
  • 12,483 posts

Posted 06 March 2015 - 09:37 PM

Great thread.


We got a 1.5kW system (and solar hot water using evacuated tubes) about 5 yrs ago.  They were a wedding present. (Well.  People chipped in cash towards it as a wedding present).


I also went on a massive 'efficiency drive' through the house.  LED lighting etc.


In summer, our electricity bill tends to be $0 or less.  In winter, it's about $100.  We tend to spend maybe $300/year (If I forget to turn off the booster for the solar hot water in winter).


The gas is much more expensive.  Heating, and heating alone. That's maybe $600/year


I still think the biggest boost in our house was my efficiency drive.  Even PC's were built around efficiency.



I can make my own woggle! Bet you can't woggle yours.

#18 Cybes



  • Atomican
  • 18,336 posts
  • Location:Where I am

Posted 06 March 2015 - 09:44 PM

That's a pretty impressive bill, AD. How much did it set you back to implement the changes?

"Reality does not care what you think." - Dr Richard Feynman
"There is no "I" in team." - "True.  I will not be found in any team."

#19 AccessDenied



  • Hero
  • 12,483 posts

Posted 06 March 2015 - 09:55 PM

How much did it set *ME* back.  Or how much would it cost?


It was a combination of Bunnings vouchers from my birthday, plus me using my electronics contacts to get trade prices in various places.


In the end, it cost maybe $200.  I consider it paid back in 4 - 6 months.


However, it was equivalent to about $800 of changes.  (That includes stuff like paying more for different mobos/powersupplies to a standard computer system).



As an addition.  I'll do it as a reply, just in case.  If it gets tacked onto my previous reply, great..


Changes include:

LED lighting (Every light!  Even the outside movement based flood lights)

Solar hot water

Low power PCs.  The media PC has a 150W PSU in it.  My main PC (this one) has a 400W PSU in it.

Insulation (lots of)

Heavy curtains (To block out heat as well as light)

Sky lights (They introduce less heat for more light.  Close the heavy curtains and let the skylights do their work!)

Purchases based on efficiency (Dishwasher, washing machine, fridge etc)


When you consider the above, hopefully it makes sense.



I can make my own woggle! Bet you can't woggle yours.

#20 scruffy1



  • Hero
  • 5,624 posts
  • Location:near the beach

Posted 06 March 2015 - 10:09 PM

good thinking above !


we just purchased a 3.5star fridge, etc, but low volt lighting is on the agenda


and all the processors are sandy / ivybridge w/o discrete video except for me :) - can't do gaming without the 7950 really, but not that often these days

mostly we use asus transformers or nexus for simple stuff


got a 100w 46" sony lcd tv - which sees movie use sporadically


ceiling fans, no aircon


having a house facing pretty much due north across a valley in the lee of the the hill sheltering us from southerlies off the harbour, with the pacific around 500m to the east is great for climate moderation too


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users