58 minutes ago, TinkerBoy said:

TTT is worried the panels wont last 20 years

Nope, you got it wrong. Not worried at all boet.

 

I do find it interesting though reading here thinking in the back of my mind that I recall most established solar installers estimate an average of +-7 years ROI on a legally installed grid tied system.

Maybe I must do the sums again for self install saves a lot of costs and buying at cost even more. But to do it legally, adds a few rands.

2 hours ago, TinkerBoy said:

... it will be almost double my total costs.

Nope, a few k more, not double.

 

2 hours ago, TinkerBoy said:

Your installers are a bit on the pricey side

Jip, let me share why I am so reluctant to go grid tied.

 

Since the first installers came about, I have had about 5 quotes the last number of years.

Now, let me set the stage. Couple of years ago we built up. Bummer with building up is that you have also redo all the lights on the lower floor. Took 5 full days and I could quantify the costs and the labour. Because we built up, I had to get engineers reports. So I am well versed what they can cost too.

Now, the quotes I got for a simple solar install, 3 panels on the roof and 1 inverter, I am quoted 5-6K per day. Parts, one installer told me they charge premium. You can get it cheaper yourself, he said, when he gave me a few spare fuses.

Then they charge a few K for sundries, and do not forget the travelling, sometimes AA+ rates, on some of the quotes I got.

Do NOT ask my how they get to these numbers. Each time I have asked I get a very snotty attitude like in how dare you question our charges? They soon realize it takes two to do this little tango.  

But that is not all ... the meter replacement! Special price ... R2.5k payable to the municipality.

And then, once all is said and done, comes the cherry on the cake. From 3 quotes in the last year, find another +-10k for the signing off the system to be able to register such at the municipality as grid tied. Turns out it costs a lot for the engineers to register to sign off these systems, and to be held responsible if something goes wrong.

And if your are unlucky, I am not, and your roof mounting becomes complicated, you could be looking at another few K for a engineers reports re. trusses, frames ito wind sheer ... they do not want panels flying off the roof knocking someone on the head, was mentioned in passing.

I cannot wait for solar installers to become as general as DIY guys and electricians, electricians who can sigh off their installs without the need of a engineering report.

 

Learned recently that in the next year or so no more self installs in Cape Town. They are getting ready to appoint installers which, as one installer recons, are going to push up the costs even more. Why?

As with all new things, I suppose these costs will come down IF more people opt for solar, but I do not see that happening anytime soon.

As I am reading through all of this a couple of thoughts jumps to mind.

As I see it you get six (maybe more ) groups of Solarlists .

1. The business guys who runs their business of solar and SAVED a boat load of money by not having to shut down during load shed times or to spend money on Diesel , petrol and maintenance on the gen-sets. BUT those days seems to be past now as we have't "officially"  had any load shed in the last year or two so IMO it would be hard pressed to get ROI in this manner  , an I say it again , in today's environment. If load shed starts up again then the obviously this changes everything but again IMO you can't use this argument for future "possibilities".....
2. The Guys who installed Inverter systems at home to combat load shed as a matter of luxury/necessity then said "hey instead of charging my batteries with Eskom why don't I do it with solar. Now this group started of as n backup plan ten evolved over to solar and now have to justify the costs incurred.They are the guys that is constantly looking to drop thier base loads push the most out of thier systems as they generally dont have the cash to constantly upgrade. My gut feeling is that they will eventually move over to grid tie or split systems where minimal battery use would be needed as the future replacement cost of the battries will force them in that direction.
3. The group of Farm/Rural guys that is spending a lot of money of line charges and is now looking into options to save money and reducing overheads in their business. They usually are very practical and is very willing to make sacrifices to be able to do what they do best and that is to farm the land. The ROI on this group is fairly easy as you have a fixed cost component in your equation.You could also add the guys that does not have Eskom or it did not make financially sence to spend the cash on Eskom.
4. Then you get a group that were wasting power and paying a premium to eskom for that , looked at the bills and looked at Solar having the the means went over to solar and then had to make the lifestyle changes to fit in with Solar. To keep on justifying the investment they will use the "old lifestyle" bill's to determine their ROI. One could argue that if it wasnt for Solar they would not change their lifestyle but IMO their calculations is wrong as you need to look at your current consumption because can do that consumption with Eskom as well. 
5. There is also the group of guys that has a boatload of money and installs the meanest system money can buy , this will give them bragging rights at the braai/fondu  , make them feel that they are more green and also contribute to the local economy. Apart for their mates that will go the same route there is no comparison....
6. One could also add they guys that has Solar as a hobby - One can never put a price on a cool hobby. As well as the okes that is gatvol of the government and is moving over as a matter of principle (One can never argue principal decisions..)

It is close to impossible to compare any one of these groups with each other as their approach to ROI is in principal not comparable. At the end of the day it is still your money that you spent and how you justify is is your own case. If you are looking into Solar as an alternative you should decide in witch group you fall in and then decide it make financially sense..

Anyway my 5c worth..

21 minutes ago, TinkerBoy said:

That is R95K more

@TinkerBoy I agree things don't add up - where did you get this value?

1 hour ago, PaulF007 said:

The business guys who runs their business of solar

 

1 hour ago, PaulF007 said:

at home to combat load shed as a matter of luxury/necessity

 

1 hour ago, PaulF007 said:

Solar as a hobby

I'm in all three those categories. Perhaps also in a seventh, which is presently still somewhat of an idea: A future career perhaps. Not many programmers understand solar energy well, and conversely, most solar installers know little about development.

9 hours ago, The Terrible Triplett said:

signing off the system to be able to register such at the municipality as grid tied

A local acquaintance of mine was looking for a partner, someone with a professional engineer qualification, to sign off his systems for him. So far he's been unable to find one. When I started asking around among the electrical/electronic engineers, the answer was that 1) the test is very difficult and the answers has to be "just so" to pass, 2) it costs a lot of money, 3) if you are registered as a professional, you can be legally sued, 4) they have found employment that pays well without going through all that schlep, 5) the guys who has that certification likely works for a big company and you will pay big bucks to get them to drive out to your place, glance over the wiring, look at the paper work for the inverter, see the VDE-AR-N 4105 text... and then sign it.

So I estimate this little exercise alone could set me back 5k. We'll see. Something really has to be done to make it easier to set up smaller systems, the ones in the <100k bracket, because you really can do it... just not the way it is being handled now.

6 minutes ago, TinkerBoy said:

 

160000 / 4.4 = 36363

36363 x 2.6 = 94543

if i had to allocate my R3k savings for 7 years  I would pay R94.5 k more   

 

 

Ok so the value is a Assumed value derived from your own personal costing and calculations and no factual information at your disposal.

 

1 hour ago, TinkerBoy said:

So one of the 2 statements does not add up. All I am saying.

I for one would be careful implying that statements does not add up if derived from your own experiences and assumed values ... 

 

All i am saying of course .....

 

1 hour ago, TinkerBoy said:

I have with my own calcs and costs

What I am keeping in mind also is that with the 7+-years ROI, on grid tie no batteries:
1) that you still have to use Eskom with the connection fee added, properly measured by the newly installed meter.
2) their calcs was based on Eskom anticipated increases, which never happened at the higher % that was estimated, making the 7+- years ROI period even longer.

What is not in their figures either:
1) the replacement costs when parts need replacing. So if a costly part fails in say year 7, you need to add more years to recoup.
2) the curve ball the installers do not push, obviously, using the customers last few, or last years Eskom bills, is not saying a word about: Reduce then solarize.

The point is that these figures are not that easy.

First let me be clear I do this for the benefit of any newcomer that are looking to go into solar energy and might be reading through all of this.

Second this is derived through pure maths and if you disagree please show calculations (Frankly I don't care about your opinion unless it is backed y figures)

So: 

Scenario you want to do a solar installation that should be paid off in 5 years and you are not using your own money , bank borrowed you the cash. Your Current Eskom bill is R 3000 per month and thus have R 3000 available to spend on a System. Bank Interest Rate will be 10.5% 

So the bank will borrow you R 235 406.74

FV = R 235 406.74 , PMT = R 3000.00 , I = 10.50% , N = 60 , END Mode 

So with a odd R 240 000 you would like to generate the following 

Lets assume Fixed Eskom Charge of R1200 and Usage fee of R 2.50

So from this we can derive the following:

(Bill - Fixed Charge) / Usage fee = Units per month

(3000-1200)/2.50 = 720 units , 720 units /30 days = 24 units per day 

Here lies your problem to generate 1kwh per hour you are going to need a lot more money to generate that amount of power to from Solar and batts (I know there is a Solar Calculator floating out there that will show what is needed to produce that amount of power please feel free to chip in or show us what R 240 000 can buy you?

So you will need to reduce your consumption so that you can "fit in" with your design after. NOW since you have reduced your  consumption you will need to revisit your calculations again as your monthly bill will be a lot lower that what you are currently paying...

In all the calculations that I have made there is no way that you can pay off your solar system in such a short time if you are purely working on consumption. Unless you have a ridiculous high fixed monthly charge but then your usage will already be very low. IF your fixed charge were to be R 2400 you would be using about 8kwh per day.....

If you have made it all the way here and is wondering "nou wat nou" the rule of thumb for solar is :

• Invest in a proper energy monitor that can do proper logging for you over a term of about 2 months 
• Start to reduce your consumption to as low as what you are willing to live with (CONSULT WITH THE MISSES ON A REGULAR BASIS)
• See your monthly Eskom bill going down,
• If you still have a wife after this exercise she should be Solar compatible and you can start to setup you solar design (Here is some terrific guys here that can assist with the design once you have done the homework)
• Be prepared to still use a little bit of Eskom at night as this will bring down your Capital cost down significantly.

 

I have just realised that this whole post has been derailed again but that seems to be the trend any way .... I will see n 20 years time if my panels is still going and then I will give feedback accordingly ...

TinkerBoy says his installation cost was 160K and savings at his time is 36K per year. Depreciate the kit over 20 years and you have "income" of 36K-8K=28K. That equals a ROI of 17.5% at present Eskom tariffs. Now imagine the average Eskom tariff over 20 years and the 17.5% ROI will look very different. Besides what investment pays this kind of dividend and capital growth. You will be hard pressed to find it on the JSE or any other stock exchange in the world over the long term. If one deducts the 36K for his batteries and put up with load shedding if and when it happens, the picture gets a whole lot more rosy.

6 minutes ago, ebrsa said:

TinkerBoy says his installation cost was 160K and savings at his time is 36K per year

@ebrsa I would love to see how that figure is calculated , as I can not for the world see how he could get to a saving of R 3000 a month if his total Consumption is about 28 - 40kwh including using the GRID - unless he is pushing back into the grid and is getting paid for it.....  

 

34 minutes ago, ebrsa said:

ROI of 17.5% at present Eskom tariffs

Hold on ... so bank loans me 160k at 10.5% interest, I install my solar system, and happily make 7% profit thereafter till the loan is repaid?

Dit kan mos nie waar wees nie?

@PaulF007 I think there are a few zeros missing. My consumption in August 2016 was 762Kwh costing R1395.79 with only my wife and I in the house. Also we saved substantially on water heating as I installed an evacuated tube heater and only rarely had to switch on the geyser for and hour or so. TinkerBoy has energy consumers like aircon and a heat pump for water heating as stated in other posts on this forum. So my guess is his consumption is probably 2800 to 4000 Kwh per month without evacuated tube heater and heat pump. He did however say that they use a lot of hot water in the home.

@The Terrible Triplett If you borrow the money the calculation is somewhat different because the bank will charge you 10.5% compound interest. If TinkerBoy saves R3000 per month, that is R36000 per year. If you depreciate R160000 over 20 years, that is R8000 per year leaving an annual saving of R28000. Divide that by R160,000 and you get 17.5%. If he leaves out the batteries and put up with load shedding, the invested capital would be R124,000. Depreciate that over 20 years and the annual depreciation is R6200 giving a surplus of R36000 - R6200 = R29800. Divide that by the invested capital of R124000 and the result is a ROI of 24.03%. TinkerBoy has a grid connected system which he explained comprehensively in another post on the forum. His batteries are only used in the event of a blackout and has at this stage to be switched manually.

I approached the matter from the point of view of having the capital to invest and then determine if the ROI is attractive or not. That is in my view the only logical way to approach the matter and there is no question to my mind that it is very attractive. You could do the calculations yourself for an instance where the capital is borrowed but then issues such as future interest rates comes into play. However I stand corrected if you can prove me wrong.

Ok so lets do the math again 

August you used 762 kwh that will give me 24.58 kwh per day 

Costing is R 1395.79 / 762 = R1.83 per unit now is this safe to assume that this is what you paid Eksom?

Then if he is saving R 3000 per month because he has solar then logic - 3000/1.83 = 1 639. 1639 kwh - putting him at 52kwh per day - SHOOT that is a hell of a lot of hot water or is that hot air......

FYI got the stats from his emon feed (Is it safe to assume that those are correct?) http://emoncms.org/JacoFourie/Power -  Now where is the ZEROS missing?

And as asked before please show how you got to the saving of R 3000 a month BEFORE you start using it as a base of measure!

 

 

 

@ebrsa 

29 minutes ago, ebrsa said:

However I stand corrected if you can prove me wrong.

You are not wrong at all, just, in my opinion, using unsubstantiated figures, R160k and 3k saving.

You are right ito compounded interest which makes my point not entirely accurate either.

Lest we forget, the true cost of a system, includes the oepsies, Tinkerboy paid a wee bit more before he settled on the Infini's, not? And turning meters back also is not a "saving" really, it is a chance you take, that when done properly, escalates the costs slightly ... if we want to get really technical here.

It is as Paul said ...

27 minutes ago, PaulF007 said:

.. as asked before please show how you got to the saving of R 3000 a month BEFORE you start using it as a base of measure!

If the figure can be substantiated, that a financial mind agrees all is taken into account, then that is absolutely fantastic and we all learn a lot here today.

I am so hoping I am wrong, that solar can be a +-17.5% ROI.

But prove that.

I say a proper installed system is +-7 years ROI, not even taking all factors into account. If I have to, I will get those quotes in again, just to want to waste solar installers time.

No that is not a great deal of consumption per day and during the winter in Pretoria he will need a lot of hot air, literally. The costings are also not so simplistic. In Swartland Municipality, where I live, for 2016/17 our tariffs are: 0-50 @ R0.9576, 51-350 @ R1.2312, 351-600 @ R1.728, >600 @ R2.0406 VAT inclusive. So as you can see if TinkerBoy is in a similar boat, and that is the case in probably all municipalities, although the tariffs and brackets may differ, the bulk of the consumption is at quite a high rate. I have often seen daily consumptions in excess of 30Kwh per day on my Owl meter with only two people in the house before we had any renewable energy feed. Also we have a gas stove in the kitchen. The moment you switch on heaters, consumption just fly up. Besides I did not get to savings of R3000 per month, TinkerBoy stated that in an earlier post and from experience I quite believe him. Without renewable energy feed I really don't think 52Kwh would be excessive in his case.

@The Terrible Triplett If you borrow the money the calculation is somewhat different because the bank will charge you 10.5% compound interest.

 

So much info here please see response in red ....

If TinkerBoy saves R3000 per month, that is R36000 per year.(PLEASE SHOW HOW YOU GOT THIS VALUE)

If you depreciate R160000 over 20 years – Does this imply that all goods will only be replaced in 20 years time and that you replace at same cost! , is inflation taken in account because @ 6% inflation if all goes well will put you at about R 513 141 future replacement value. This , in strait line , will give you about R25000 per year.

, that is R8000 per year leaving an annual saving of R28000. Divide that by R160,000 and you get 17.5%. – Just flawed all together

If he leaves out the batteries and put up with load shedding

the invested capital would be R124,000. Depreciate that over 20 years and the annual depreciation is R6200 giving a surplus of R36000 - R6200 = R29800. Divide that by the invested capital of R124000 and the result is a ROI of 24.03%. – Refer to top,

TinkerBoy has a grid connected system which he explained comprehensively in another post on the forum. His batteries are only used in the event of a blackout and has at this stage to be switched manually.- Ok confirmed that Eskom will still be used so THAT R 3000 saving is only for daytime usage?

I approached the matter from the point of view of having the capital to invest and then determine if the ROI is attractive or not. That is in my view the only logical way to approach the matter and there is no question to my mind that it is very attractive. You could do the calculations yourself for an instance where the capital is borrowed but then issues such as future interest rates comes into play. However I stand corrected if you can prove me wrong – The offer was made so here goes.

It is quite simple if you invest R 160 000 and you get R 36000 from it it will give you a single line ROI of 22.5% - R 36 000 / R 160 000 * 100 ( No need to bother with depreciation)  BUT and I can not state this more – FIRST show how the R 3000 per month was determined THEN we can get the proper ROI....

The only reason why I hammer this is , it is silly to come up with figures that can not be quantified and then proclaim that Solar will give you a ROI of 17%. Being people as they are they will always look at the most favorable info and make life decisions on it. I am willing to state to a FACT that there in NO way that you can get a 17% ROI on any solar installation.

However I stand corrected if you can prove me wrong......

@The Terrible Triplett If, in your view, a renewable energy installation will pay for itself in 7 years, that would be 100/7 = 14.29% ROI. Still not a shabby return I would suggest. In any event it was an interesting exchange of views. Lets see how it develops further if at all. In my humble view, the cost of the equipment should be amortized over its useful life. That is standard accounting practice. If you do that you will undoubtedly find that the amortization per year is much less resulting in higher savings compared to grid consumption. Of course the picture will change when you add battery costs to the calculation, particularly if their lifetime is not maximized with optimal care. Following the suggested method will give you an accurate ROI and a sound basis for decision making. Otherwise how do you account for the many years of savings after the initial 7 or so to pay for the installation.

As a side note Studies in the US shows that with "incentives" most systems would be paid back in excess of 9 years but it is also notes that this varies from state to state.

https://cleantechnica.com/2014/02/01/real-cost-solar/

 

 

@PaulF007 Paul I agree with you that the future value or replacement cost of the equipment will be R513,141 at 6% inflation. I don't fathom why you think that a return of R28,000 per year on R160,000 = 17.5% is a flawed calculation. Also R2333, the monthly savings, invested for 20 years at 5% = R959 079 which would cover the replacement costs. Of course I made the assumption that solar panels, the major cost in the installation will last for 20 years. The inverters may not and the batteries certainly will not. However flawed you may regard my reasoning to be, it does make a compelling case for renewable energy. Let me ad that I am certainly not one of the hysterical renewable energy activists and surely don't like wasting money. However just to help you to comprehend TinkerBoy's system, as I understand it. His load is connected to the Infini input and his solar panels feed the grid via the Infini grid tied inverter. That is why he has to switch to batteries manually in case of a blackout. Battery or solar power does not directly feed his load. If you search for it, you will find a video explaining the system clearly.

Perhaps some more analysis and realistic assumptions regarding the expected lifetimes of the various components and replacement costs will give a more accurate picture of the financial implications. However, the ever increasing Eskom electricity tariffs and decreasing costs of solar equipment, makes a compelling case for installation of renewable energy. In my own case I am simply trying to cater for the continuous load of the house and not the peaks of high energy consuming appliances.

Just saw your note regarding systems in the USA. Well the amount of sunshine varies hugely between Maine and Texas and certainly in RSA we generally do not have a shortage of solar radiation. So maybe @The Terrible Triplett suggestion of 7 years is not unrealistic.

30 minutes ago, ebrsa said:

.. suggestion of 7 years is not unrealistic

Not my first time I am having this debate. 

Want to re-iterate, you are touching on it ERBSA, that although the +-7 year calcs are closer, they still lacked factors like you touched on i.e. no equipment depreciation / replacement, worked on higher Eskom increases over years that did not materializing in real life and that panels start degrading at +-10 years as per (depending on make) most manufacturers warranties.  

What also struck me with the +-7 years ROI was that one is going to use Eskom, and they say that you must make sure you use all the power in the day, so if you are a family, all out to work in the day and using power mainly at night, the ROI is not 7 years.

What also was left out was irradiation figures per year where one lives (facepalm) ... never thought of that till now. See you also touched on that ERBSA.

It is a literally whole calc or no calc scenario, that needs new figures each time there is a change to keep the ROI realistic, like the investment guys calc on monies invested.

 

So I am wondering, just putting it out there, why don't we all put in our knowledge and expertise and craft a Excel document to take into consideration all the possible costs for a solar system, taking into account how much solar you need to make the best possible ROI? 

1 hour ago, ebrsa said:

I don't fathom why you think that a return of R28,000 per year on R160,000 = 17.5% is a flawed calculation

Oh for sure you are correct 28k return on a R 160k investment is 17.5% return on investment. My bad sorry ..... ... ... 

1 hour ago, ebrsa said:

Also R2333, the monthly savings, invested for 20 years at 5% = R959 079 which would cover the replacement costs.

Also correct if you invest R 2333 for 20 years @ 5% you will have R 959 079 

 

1 hour ago, ebrsa said:

However just to help you to comprehend TinkerBoy's system,

Thank for the offer but I do understand the system as I myself is quite interested in Grid tie only thing is i don't have Eskom - Grrr

1 hour ago, ebrsa said:

his solar panels feed the grid via the Infini grid tied inverter.

Cool if I remember he is in Gauteng but , stand to be corrected. I wasnt aware that you could feed back into the grid but this is a REAL game changer and will retract all statements if he gets paid for the power that he produces in fact I would love to see how that is working. Just a word of Caution if the system is not designed for something like that and city power shuts down for maintenance and you feed back from the wrong side and some one does gets electrocuted you will most likely look at a manslaughter charge , use it dont use it I dont care.

1 hour ago, ebrsa said:

However, the ever increasing Eskom electricity tariffs and decreasing costs of solar equipment, makes a compelling case for installation of renewable energy.

I am in agreement else this Forum would not exist.

 

To conclude the Issue was NEVER if you can get ROI on solar , we all know it does. The concern is/was that the figures from which the base of argument was used does not seem to add up so to speak. Hence why the initial question was and still is how was the savings value determined.

Thats me on the subject.

I'll agree with one thing you guys all said, sort of between the lines sometimes. Something I experienced myself. After you do the whole reduction phase where you reduce consumption to make the solar bit cheaper... you will realise that you actually save way more money (and get a better ROI) on any money you spend on THAT phase.

Redo the math after that and it's like... pfffft, this suddenly makes so much less sense :-)

Also, 50kwh a day isn't a lot for a large house. Well, it IS a lot, but it might be sort of ballpark if you know what I mean. When I moved into this house in 2010 we did a consistent 40kwh a day. I thought nothing of it as electricity was still (relatively) cheap and we had always used 20kwh in our previous house (which was less than half the size of this one). Then one day the old mathematical noodle kicked in and I was like... you know, at 40kwh a day that's pretty close to a constant 2kw... and you don't even have a pool pump to blame. So now I'm back to about 20kwh... in summer. In winter (August mostly)... we touch 60kwh on Tuesdays, which is clean-the-house-and-laundry day.

So I have another angle here: With equipment that was paid for by recovered work hours during load shedding... what can I do with my present equipment to lower my 20kwh even more? So that's what the whole hub-4 journey is about right now. If I spent 20k to grid-tie my existing system (which I can do, because it's blue), and if I already had a 3kwp array (which I don't, but lets pretend), what would the ROI on that be? roughly 15kwh a day, at roughly R2/kwh, so R30 a day, assume 200 shiny days, that's R6000 a year. So 4 years thumbsuck... best case scenario.

Local installer tells me a GTI system is now around 5 years. Installers tend to paint the picture a bit more rosy.

Hence... for now, I will treat numbers < 5 years as suspect :-)

@plonkster You have formulated the dilemma as it occurs in real life very accurately. My reasoning before installing solar was pretty much the same. Initially I installed an evacuated tube heater for domestic hot water and that cut a significant chunk off the grid consumption. An Owl meter showed my ongoing consumption to be around 1Kw. So I installed 2x 4Kw Axperts, simply because I did not want to rewire the house, with 225AH battery capacity to be able to utilize excess solar generation and take care of blackouts ( Eskom euphemistically calls it load shedding). Solar power is generated by 9 x 250W panels which keeps the batteries charged and on reasonably sunny days produces enough for the base load for lack of a better term. The peak demands and supply when the batteries reach 80% DOD is left to the grid. This is all controlled admirably by AICC.

I ruled out a grid-tie system or a hybrid inverter like the Infini, which has connection for batteries, as our municipality pays R0.685 for electricity fed to the grid and charges R1.18 for consumption. Also they only allow credit equal to consumption on a monthly basis. So one has to generate 72.26% more than consumption just to break even. A friend whose son owns a house in Brighton UK, tells me that his son is paid for installed capacity irrespective of what he consumes or feeds into the grid. We can only dream.

One also has to consider the ROI which is not the same as the amortization period. If you can get a better ROI on another investment then it makes sense to pay Eskom for consumption. It is my view that ROI is the only logical consideration. Why would one spend a pile of money to save say 10% on it in grid consumption charges when you could for example invest the capital in an investment that yields say 12%. You would be losing 2% per year. The whole discussion was triggered by what @TinkerBoy said he was saving per month and your statistics refutes the questions raised about the validity of his data. The way in which his system operates makes absolute sense but I doubt he would do it at the rates of our municipality. He is really just using the grid as a giant battery which is the purpose of grid-tie inverters. Since his Infini allows for connection of batteries, he also has power during blackouts which is the major purpose of batteries connected to a grid-tie inverter. It would also seem that @PaulF007 is unaware that grid tied inverters incorporate circuitry to disconnect them immediately from the grid in the event of the grid going down. So while his caution regarding electrocution is probably well intended, it does not apply.

@The Terrible Triplett suggested the creation of a spreadsheet to calculate the economical feasibility of solar systems, which would surely benefit many. However the variables such as the variety of items of equipment used and various expected life spans will make it quite a task. However if individuals construct their own and factor in elements such as cost of equipment, amortization period of components, savings on tariffs etc. they could come to an informed answer in calculating either the ROI or period of amortization. Perhaps if we all share some more information about system components and electricity tariff structures we could in time cobble together such a spreadsheet.