let's talk about battery banks- I reckon the "they aren't worth it" thing is wrong

[PVfarmer]

Why don't you calculate the 3 different scenarios (A: POCO, B: PV-only, C: PV+Batteries) the way you'd like to using the previous values ($.15/kwh for buying/selling power with POCO, $.10/kwh for storing power, $.01/kwh for PV LCOE vs. $.14/kwh for PV LCOE). Most likely you'll find that PV-only is the clear winner in both those scenarios. If somehow you come to the conclusion that option C is the best choice please share your calculations and we can explain where you've gone wrong.

Scenario A: I buy from the POCO (no solar, no batteries)
Scenario B: I generate the power, sell the power and buy it back at the same price
Scenario C: I generate the power, I put it into batteries and then use it.

10kWh a night. LCOE=14:
A = You pay $1.50 a night with no PV.
B = You paid $1.40 for that generated. You sold AND bought it for $1.50. You lost 10 cents there.
C = $1.40 generated + $1.00 storage *minus* the $1.50 not bought = You lost 90 cents

10kWh a night. LCOE = 10:
A = $1.50
B = You paid $1. You sold AND bought for $1.50. You lost 50 cents.
C = You paid $2 minus the $1.50 not bought = you ALSO lost 50 cents.

10kWh a night. LCOE=1
A = the same
B = You paid 10 cents for that generated. You sold/bought it for $1.50. You lost $1.40.
C= 10 cents generated + $1.00 storage *minus* $1.50 = You MADE 40 cents.



Batteries won, because just as I said in the OP, the third example C where you made 40 cents is the only one where cost of PV + BESS is LESS THAN the POCO price!

The grid CAN be a free battery, but it most assuredly is NOT always!

 

[PVfarmer]

corrections but no change to result

corrections but no change to result

This is the right one. Too late to edit the previous one.
Still the same result, sorry if anyone was upset by the "mistake".

Scenario A: I buy from the POCO (no solar, no batteries)
Scenario B: I generate the power, sell the power and buy it back at the same price
Scenario C: I generate the power, I put it into batteries and then use it.

10kWh a night. LCOE=14:
A = You pay $1.50 a night with no PV.
B = You paid $1.40 for that generated. You paid zero during the day You paid 75 cents at night. You lost 75 cents there.
C = $1.40 generated + $1.00 storage *minus* the $1.50 not bought = You lost 90 cents

10kWh a night. LCOE = 10:
A = $1.50
B = You paid $1. Daytime is free, you still paid 75 cents at night. You lost 25 cents.
C = You paid $2 minus the $1.50 not bought = you lost 50 cents.

10kWh a night. LCOE=1
A = the same
B = You paid 10 cents for that generated. You still paid 75 cents at night. You lost 65 cents
C= 10 cents generated + $1.00 storage *minus* $1.50 = You MADE 40 cents.



Batteries won, because just as I said in the OP, the third example C where you made 40 cents is the only one where cost of PV + BESS is LESS THAN the POCO price! <--edit: the price POCO *charges*

The grid CAN be a free battery, but it most assuredly is NOT always!

 

[TommyO]

Scenario A: I buy from the POCO (no solar, no batteries)
Scenario B: I generate the power, sell the power and buy it back at the same price
Scenario C: I generate the power, I put it into batteries and then use it.

10kWh a night. LCOE=14:
A = You pay $1.50 a night with no PV.
B = You paid $1.40 for that generated. You sold AND bought it for $1.50. You lost 10 cents there.
C = $1.40 generated + $1.00 storage *minus* the $1.50 not bought = You lost 90 cents

Ok - I have bolded and underlined where you made a mistake.
$1.40 - $1.50 + $1.50 = $1.40
$1.40 is less than $1.50
Therefore you SAVED 10 cents.

10kWh a night. LCOE=1
A = the same
B = You paid 10 cents for that generated. You sold/bought it for $1.50. You lost $1.40.
C= 10 cents generated + $1.00 storage *minus* $1.50 = You MADE 40 cents.

Again you've inverted the sign on the result for scenario B.
You have SAVED $1.40 compared to scenario A.

It only makes sense that if your PV system is CHEAPER that you SAVE MORE.
By inverting the sign it looks like if your PV system is cheaper ($.01/kwh) that you have a larger expense compared to just buying from the POCO - and obviously that'd just be wrong.

Batteries won, because just as I said in the OP, the third example C where you made 40 cents is the only one where cost of PV + BESS is LESS THAN the POCO price!

The grid CAN be a free battery, but it most assuredly is NOT always!

In this case it certainly IS a free battery - it's just that you made a mistake in your math and reached the incorrect conclusion.

 

[winnie]

I am just commenting on one scenario calculated; the others have the same error and need the same correction:

10kWh a night. LCOE=14:
A = You pay $1.50 a night with no PV.
B = You paid $1.40 for that generated. You sold AND bought it for $1.50. You lost 10 cents there.
C = $1.40 generated + $1.00 storage *minus* the $1.50 not bought = You lost 90 cents

In step A the net cost is $1.50

In step B you do not lose 10 cents. You 'pay' $1.40 for the generated power. You sell it to the POCO and earn $1.50. You buy it back from the POCO for $1.50. Net total cost of $1.40 (a savings of $0.10 versus baseline)

In step C it is not correct to subtract the $1.50. You are trying to calculate the _total_ costs paid to get 10kWh of electricity at night. This is simply the cost of generation plus the cost of storage, for a total of $2.40. (a cost of 90 cents more than baseline; you didn't lose 90 cents; you paid 90 cents more for the electricity)

When you make this correction to all of your scenarios, the batteries do not win in any of them.

-Jon

 

[TommyO]

This is the right one. Too late to edit the previous one.
Still the same result, sorry if anyone was upset by the "mistake".

You were closer before other than a sign mistake.
But let's use your new scenario with 5kwh during daylight, 5kwh at night.

> B = You paid $1.40 for that generated. You paid zero during the day You paid 75 cents at night. You lost 75 cents there.
You paid $1.40 for what's generated.
You used 5kwh directly ($0)
You sell 5kwh to POCO during the day (-$.75)
You buy 5kwh from POCO during the night ($.75)
$1.40 - $.75 + $.75 = $1.40

And $1.40 vs. $1.50 means you saved $.10 compared to scenario A.

 

[PVfarmer]

10kWh a night. LCOE=14:
A = You pay $1.50 a night with no PV.
B = You paid $1.40 for that generated. You sold AND bought it for $1.50. You lost 10 cents there.
C = $1.40 generated + $1.00 storage *minus* the $1.50 not bought = You lost 90 cents Ok - I have bolded and underlined where you made a mistake.
$1.40 - $1.50 + $1.50 = $1.40
$1.40 is less than $1.50
Therefore you SAVED 10 cents.

10kWh a night. LCOE=1
A = the same
B = You paid 10 cents for that generated. You sold/bought it for $1.50. You lost $1.40.
C= 10 cents generated + $1.00 storage *minus* $1.50 = You MADE 40 cents.


Again you've inverted the sign on the result for scenario B.
You have SAVED $1.40 compared to scenario A.

Ok - I have ALSO bolded and underlined where you AND I made a mistake.
I will fully admit "lost" on my part was the wrong word- so I fixed it.
$1.40 - $1.50 + $1.50 = $1.40
$1.40 is less than $1.50
Therefore you SAVED 10 cents.

"-$1.50+$1.50" is the mistake.

This is draft #3, I think this is really it.

Scenario A: I buy from the POCO (no solar, no batteries)
Scenario B: I generate the power, sell the power and buy it back at the same price
Scenario C: I generate the power, I put it into batteries and then use it.

10kWh a night. LCOE=14:
A = You pay $1.50 a night with no PV.
B = You paid $1.40 for that generated. You paid zero during the day You paid 75 cents at night. You really paid 75 cents there.
C = $1.40 generated + $1.00 storage *minus* the $1.50 not bought = You really paid 90 cents

10kWh a night. LCOE = 10:
A = $1.50
B = You paid $1. Daytime is free, you still paid 75 cents at night. You really paid 25 cents.
C = You paid $2 minus the $1.50 not bought = you really paid 50 cents.

10kWh a night. LCOE=1
A = the same
B = You paid 10 cents for that generated. You still paid 75 cents at night. You really paid 85 cents
C= 10 cents generated + $1.00 storage *minus* $1.50 = You MADE 40 cents.

Batteries won, because just as I said in the OP, the third example C where you made 40 cents is the only one where cost of PV + BESS is LESS THAN the POCO price! <--edit: the price POCO *charges*

The grid CAN be a free battery, but it most assuredly is NOT always!

Addendum:
10kWh a night. LCOE=17 POCO = 15
A = You are paying .17 * 5 (85 cents) during the day and .15 (75 cents) at night = $1.60 a day, really paying .10
B = You are paying 85 during the day AND 85 at night = $1.70, really paying .20
C = You are paying $2.70 night+ day total MINUS 75 cents not paid at night = $1.95, really paying .45

10 KWh. LCOE =15 and POCO =15
A = $1.50- really paying $1.50
B = $1.50 - 75 at night, really paying .75
C = You are paying $1.50 + $1.00/BESS minus $1.50 = one dollar.

*Any* of the above are a GOOD thing, because you are paying less than $1.50...but...
10kWh a night. LCOE=1
C= 10 cents generated + $1.00 storage *minus* $1.50 = You MADE 40 cents.

Still stands, and in conclusion, "No - you're still wasting your time if it's $.01/kwh or $.14/kwh" is not a correct statement.

 

[TommyO]

"-$1.50+$1.50" is the mistake.

No - that was correct.

This is draft #3, I think this is really it.

Scenario A: I buy from the POCO (no solar, no batteries)
Scenario B: I generate the power, sell the power and buy it back at the same price
Scenario C: I generate the power, I put it into batteries and then use it.

10kWh a night. LCOE=14:
A = You pay $1.50 a night with no PV.
B = You paid $1.40 for that generated. You paid zero during the day You paid 75 cents at night. You really paid 75 cents there.
C = $1.40 generated + $1.00 storage *minus* the $1.50 not bought = You really paid 90 cents

Ok - let's fix B and C.

I assume from your math that you have changed the scenario that instead of 10kwh at night you're now using 5kwh during the day, 5kwh during the night.

B:
You paid $1.40 for what's generated.
You used 5kwh directly ($0)
You sell 5kwh to POCO during the day (-$.75)
You buy 5kwh from POCO during the night ($.75)
$1.40 - $.75 + $.75 = $1.40

And $1.40 vs. $1.50 means you saved $.10 compared to scenario A.

C:
You paid $1.40 for what's generated.
You used 5kwh directly ($0)
You store 5kw into batteries ($0)
You retrieve 5kwh from batteries during the night ($.50)
$1.40 + $.50 = $1.90

So $.40 extra cost compared to scenario A

Still stands, and in conclusion, "No - you're still wasting your time if it's $.01/kwh or $.14/kwh" is not a correct statement.

Still correct - we just need to fix your misunderstanding of the math.

 

[jaggedben]

I think perhaps the problem here, PVfarmer, is that you don't understand how a grid-tie inverter actually works, and how much energy goes where, and when.

 

[PVfarmer]

I assume from your math that you have changed the scenario that instead of 10kwh at night you're now using 5kwh during the day, 5kwh during the night.

B:
You paid $1.40 for what's generated.
You used 5kwh directly ($0)
You sell 5kwh to POCO during the day (-$.75)
You buy 5kwh from POCO during the night ($.75)
$1.40 - $.75 + $.75 = $1.40

And $1.40 vs. $1.50 means you saved $.10 compared to scenario A.

C:
You paid $1.40 for what's generated.
You used 5kwh directly ($0)
You store 5kw into batteries ($0)
You retrieve 5kwh from batteries during the night ($.50)
$1.40 + $.50 = $1.90

So $.40 extra cost compared to scenario A


Still correct - we just need to fix your misunderstanding of the math.

Nope! You need to admit that BESS + PV + netmetering is a good thing, when (again) the cost of the PV + BESS is < POCO price.
Then you can go right ahead and use energy at night, at the LOWER cost of PV+BESS, and NOT PAY the higher POCO rate!!
:happyyes:

So- I don't recall any mention from you of daytime usage, don't see how analyzing "only night time usage" really tells the whole story.
Obviously, percentage of usage daytime vs night time is an important factor. Very important!
Was daytime use zero in your scenarios? If your 10kWh a night thing also used 10kWh during the day, this 5/5 deal is ½ the size, same LCOE, etc.

But, with a LCOE of 15 cents...
10kWh a NIGHT (which is ~half a day) * 365 * (20 years/2) = 36500kWh
You paid $10,950 for a system that puts out 3.6MW a year- that sounds VERY wrong.
Since PV mostly (100%) works during the day time, the daytime is a factor!
Paying $10,950 for 7.2MWh a year- much better.
7.2MWh a year works out to 19.73kWh a day, btw...

The LCOE does include the whole 24 hours of the day!

Also...when you've paid for something AND used it, you are done. Directly (0) is the problem, you're adding a step there.
---
B:
You paid $1.40 for what's generated.
You used 5kwh directly ($0)
You sell 5kwh to POCO during the day (-$.75)
You buy 5kwh from POCO during the night ($.75)
$1.40 - $.75 + $.75 = $1.40

You *really* paid 70 cents directly for what you used- it says so one line above it!
You ALSO sold/bought to/from POCO at a ->>>70 sell 75 buy ratio (meaning you paid 75 cents when you bought it back, so not free IN THIS CASE, it cost you 5 cents!), and paid $1.45 total, saving 5 cents.
When you sell something that cost you 14 cents to someone for 15 cents and then buy it back from them for 15 cents- you have given them a penny, just because you are a nice guy, I guess?
---
C:
You paid $1.40 for what's generated.
You used 5kwh directly ($0)
You store 5kw into batteries ($0)
You retrieve 5kwh from batteries during the night ($.50)
$1.40 + $.50 = $1.90

You paid 70 cents for what you used directly during daytime, plus $1.20 for the nighttime kWh to put it into BESS (50+70) and there is NO BILL. $1.90 - $1.50 = 40 cents.
---

I did make a mistake previously- starting with "$1.40 generated" in this below, $1.00 should be 50 cents, and 90 should be 40 cents. You used 5kWh from storage @ 10 cents/kWh.

You generated it, generating it cost $1.40- it cost 50 cents coming out of storage for the 5kWh worth. That's $1.90. Minus $1.50 (no bill) is 40 cents

10kWh a night. LCOE=14:
A = You pay $1.50 a night with no PV.
B = You paid $1.40 for that generated. You paid zero during the day You paid 75 cents at night. You really paid 75 cents there.
C = $1.40 generated + $1.00 storage (really 50 cents) *minus* the $1.50 not bought = You really paid 90 cents (nope, 40 cents).

 

[iwire]

I have no idea how to do the calculations but I have a good idea how things work when money can be made or saved.


It is a huge country with a great many grid tied systems being installed.

That being the case if, and where batteries made $ sense they would be installed.

People's love of money always shakes out the most efficient ways of doing things.

 

[ggunn]

Nope! You need to admit that BESS + PV + netmetering is a good thing, when (again) the cost of the PV + BESS is < POCO price.

OK, I am officially blue in the face here.

Net metering means that you push energy into the grid and pull it back out at no cost to you. You don't sell it and buy it back; there is no sales transaction until the utility reads the meter at the end of the month, and then all they are concerned about is the net energy transfer for the month; they neither know nor care how many kWh's you have pushed in and taken out of the grid. It's what the "net" in net metering means.

Grid storage under net metering is free; it costs nothing. There's no way battery storage and recovery costs less than nothing. There is no amount of ciphering and moving numbers around that is going to change that. Your so-called math is meaningless.

But hey, do what you want; it's your money. Go out and plunk down several thousand bucks for batteries, battery inversion, conductors, transfer switch, and protected loads panel, and pay for the labor to wire it all up and move all those loads around... and then try to make money by playing shell games with the utility. It's not going to work but you are welcome to try. There's no way in hell I would ever do something like that.

 

[TommyO]

Nope! You need to admit that BESS + PV + netmetering is a good thing

Except it isn't...

When you sell something that cost you 14 cents to someone for 15 cents and then buy it back from them for 15 cents- you have given them a penny, just because you are a nice guy, I guess?

???????

If I have a carrot, and I sell it to you for $.15
Then 8 hours later I buy the carrot from you for $.15, have I given you a penny?
No. You have exactly the same amount of money you had before you bought the carrot from me.

What if instead of a carrot it's a kilowatt-hour that I sell and then buy back?

(Answer should be "It's the same")

You generated it, generating it cost $1.40- it cost 50 cents coming out of storage for the 5kWh worth. That's $1.90. Minus $1.50 (no bill) is 40 cents

Right - $1.90 is 40 cents MORE than it'd cost if you were just buying from the POCO.

B = You paid $1.40 for that generated. You paid zero during the day You paid 75 cents at night. You really paid 75 cents there.

No - you paid $.75 and GOT paid $.75 credit from the POCO.
$.75 income, $.75 expense == $0
So you paid $1.40 for the day AND night (compared to $1.50 for scenario A or $1.90 for scenario C)

 

[PVfarmer]

I think perhaps the problem here, PVfarmer, is that you don't understand how a grid-tie inverter actually works, and how much energy goes where, and when.

That isn't really very helpful.
Would you care to clear things up for me?
You said:
"You are clueless, but I'm not going to tell you why or how or even give any evidence of why I think you are clueless"

Gee, thanks for the thought, dude!
:huh:
So now I guess I'm trolling you by asking "what do you mean"?

One thing I know about grid-tied inverters is that they don't work without a grid!
Pretty good selling point for BESS right there.
Is there something specific about GTIs that you would like to test me on so I can prove myself?

I can tell you GTIs don't play well with BESS- for BESS you either need a hybrid inverter, or if there is already a GTI in place, you'd have to weigh the myriad of options of how to add the BESS, possibly by trying to find some helpful input from other people. Hmm.

how much energy goes where, and when.

Have I got this right at least? Without a BESS, *all* of the energy goes *into the grid* during the *day*. Seems like a pretty solid statement there, with how where and when included.

So it follows that having a PV system which puts out energy that costs you 10 cents a kWh during the day, and buying that "same" stuff back at night from the POCO for 15 cents, is not good!

 

[PVfarmer]

OK, I am officially blue in the face here.

Net metering means that you push energy into the grid and pull it back out at no cost to you.
Grid storage under net metering is free; it costs nothing.

So then... you got the energy for free!
That is what those last two sentences say.

But you didn't- unless of course your PV system has already paid back for itself.

 

[PVfarmer]

???????

If I have a carrot, and I sell it to you for $.15
Then 8 hours later I buy the carrot from you for $.15, have I given you a penny?
No. You have exactly the same amount of money you had before you bought the carrot from me.

What if instead of a carrot it's a kilowatt-hour that I sell and then buy back?

(Answer should be "It's the same")

Where'd the carrot come from?

The answer is only "it's the same" IF you paid 15 cents for the carrot!
I said that you paid 14 cents for the carrot and bought it back for 15- for no reason.
If the carrot cost you 10 cents, and you "sold and bought" it to/from me for 15 cents, you gave me a nickel for no reason, thanks!
If you grew the carrot in your garden and it cost 1 cent for the seed and 2 cents for the labor, would you say "hey, here's a carrot for 15 cents"...and buy it back for 15?
I sure hope not!

(You already had the carrot/kWh "in your pocket" for 10 cents. Someone gave you 15 cents for it. Then you gave them the 15 cents back. The carrot is still worth 10, you gave them a nickel to "keep it safe" for a while.)

 

[iwire]

OK, I am officially blue in the face here.

Net metering means that you push energy into the grid and pull it back out at no cost to you.

Grid storage under net metering is free; it costs nothing.

So then... you got the energy for free!
That is what those last two sentences say.

But you didn't- unless of course your PV system has already paid back for itself.

Guys, give up on PV farmer, he is either screwing with you or incapable of rational thinking.:roll:

 

[TommyO]

(You already had the carrot/kWh "in your pocket" for 10 cents. Someone gave you 15 cents for it. Then you gave them the 15 cents back. The carrot is still worth 10, you gave them a nickel to "keep it safe" for a while.)

No - I "borrowed" $.15 from them for 8 hours and they "borrowed" the kwh/carrot from me and then we exchanged them back.

If I buy it from Vern for 10 cents, then I sell it to Polly for 15 cents, then I buy it back from Polly for 15 cents, does Polly have an extra nickel from that?
NO!

Here, let's try it a little different.
I have a house that I bought for $100k, I sell it to PVFarmer for $150k. And we have a contract that I will buy it back for $150K (and PVFarmer must sell it to me for $150k). And I buy the house back for $150k 8 hours later.
Now, are you (PVFarmer) $50k richer?

If so, why?
If not, is it different when you move the decimal place and it's a kwh? If so, why?

 

[ggunn]

Originally Posted by ggunn
OK, I am officially blue in the face here.

Net metering means that you push energy into the grid and pull it back out at no cost to you.

Grid storage under net metering is free; it costs nothing.

So then... you got the energy for free!
That is what those last two sentences say.

But you didn't- unless of course your PV system has already paid back for itself.

I don't know why I am doing this, but what the...? Either you did not comprehend a word of what I said or you are indeed screwing with me.

I'll try once more and then I'm done.

With net metering your PV system produces energy and what you don't use yourself gets pushed into the grid. You get it back at night when your PV system is not producing anything. The grid doesn't buy it from you and you don't buy it from the grid. It's JUST LIKE A BATTERY, only it doesn't cost you anything; it's FREE. If you bought batteries and everything that is needed to connect them to your service it would cost you a LOT OF MONEY to run your entire house, even at night. FREE is ALWAYS LESS than a LOT OF MONEY. And the cost of energy from the grid HAS NOTHING WHATSOEVER TO DO WITH IT.

This is really simple stuff. If you can't get this through your head, I cannot help you. I advise you to either take some classes to find out how this stuff actually works or find another hobby.

I'm done now.

 

[PVfarmer]

I "borrowed" $.15 from them for 8 hours and they "borrowed" the kwh/carrot from me and then we exchanged them back.

I have a house that I bought for $100k, I sell it to PVFarmer for $150k. And we have a contract that I will buy it back for $150K (and PVFarmer must sell it to me for $150k). And I buy the house back for $150k 8 hours later.
Now, are you (PVFarmer) $50k richer?

If so, why?
If not, is it different when you move the decimal place and it's a kwh? If so, why?

That still doesn't say anything about where the carrot came from or what it cost/is worth. If it grew wild and you found it, it would be free. If it was organic and you bought it at Whole Foods it might cost 50 cents.

It's fairly obvious there that you bought a house for 100k, sold it to me for 150k, bought it back for 150k, and there was no reason to do that at all.
When you buy back a house, you have a house. When you buy back electricity, you used it- it is then gone.
With net metering, you are not "selling kWh"- there is no monetary value put on the meter turning backwards. It is X number of kWh credit. There IS a charge for getting it back when you exceed that credit.

I'm not any richer on the house exchange because it isn't a sensible or logical thing to do. People don't really do that.
It is different when it is a kWh- the main reason why is that people don't consume houses, but they do consume kWh.

You have a house which cost X, you sell it for Y and buy it back for Y- you still have a house. It is a large object that doesn't move.
You have kWhs which cost X (X= LCOE), you are credited a kWh for each extra produced, and buy them back for Y if credit exceed- kWhs aren't objects, and they move around a lot.

The people hurt the most by this problem are those trying to offset their bills instead of have a zero bill- doesn't that describe the majority of residential PV?

 

[PVfarmer]

With net metering your PV system produces energy and what you don't use yourself gets pushed into the grid. You get it back at night when your PV system is not producing anything. The grid doesn't buy it from you and you don't buy it from the grid. It's JUST LIKE A BATTERY, only it doesn't cost you anything; it's FREE. If you bought batteries and everything that is needed to connect them to your service it would cost you a LOT OF MONEY to run your entire house, even at night. FREE is ALWAYS LESS than a LOT OF MONEY. And the cost of energy from the grid HAS NOTHING WHATSOEVER TO DO WITH IT.

This is really simple stuff.

No, it isn't simple- you're only talking about systems where the daily PV output = 24 hour usage for instance.

You don't "get back" the actual energy you produce- you get a credit per extra kWh- that actual extra kWh goes down the street and someone else pays the POCO retail for it.
A BESS stores the energy on site, and you use that same energy! Both the physical and financial processes are completely different with BESS.

Thanks for trying. That last part in italics sure isn't going to convince me of anything. I understand you have an opinion- I don't agree.
You don't mention anything I can really respond to.

If you bought a BESS and equip it would cost you a lot of money, free is better than paying money, and the rate the POCO charges has NOTHING WHATSOEVER to do with PV system economics.
So then probably the amount of energy you'd use at night has no relation to the cost of BESS- it's always approximately a LOT OF MONEY.
Thanks for the advice, I'll keep all that in mind.