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

[PVfarmer]

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

The limit of profitability is the point of intersection of the curves of the retail price and mean electricity cost.
That means, investing in a PV battery system is profitable as soon as the mean electricity cost is below the retail price.

The Germans know what's what.
https://pvspeicher.htw-berlin.de/wp...ttery-Systems-in-the-Self-Consumption-Age.pdf

"Mean cost" there is the sort of the same as LCOE.
The LCOE of the batteries/battery inverter, etc. is the important thing.
You have to *use* the batteries- if they're just used for backup when the grid goes down, they'll take forever to pay for themselves, maybe never.

For instance-
People seem to think it's wrong to put power into batteries when you could just sell it straight to the grid, but with no battery bank, at night you are using up a lot of what you "sold" that day.
So, say you are paying 20 cents for power, and getting paid 25 cents for what you put in.
So you're losing a nickel by not putting that power straight into the grid....BUT, the sun is free in the first place, so that 5 cents is really part of the LCOE.
What you're really paying over time with batteries is: the LCOE minus what you would have paid the grid, which should be a negative number.

LCOE = Total Life Cycle Cost / Total Lifetime Energy Production

If the battery system costs $3000, and you are using it to replace 7kWh every night...a little under 58A at 120V, or 145A at 48V(batteries/bank=400A total, 145A=27% average drain).

7kWh * 365 =2555kWh a year.
If the batteries only last 6 years that's 15330kWh over the lifetime.
That's a LCOE of 19.5 cents - less than 20 cents!
That's a pretty weak LCOE, and you're still ahead by a half a cent.
Even if the battery system is $4000 and the LCOE is 26 cents, you're still paying 6 instead of 20...

Knock the LCOE down another nickel, and you're *making* 5.5 cents on the stored power- not losing a nickel by storing it for later.

 

[GoldDigger]

And in Texas you only pay POCO 7 cents per kWh, so it still varies from place to place.

With net metering, you generally pay the same or less for off peak power than you are paid for your on peak surplus, so selling it back is cheaper than putting it into a battery bank.
Again, it varies from place to place.

 

[TommyO]

The Germans know what's what.

What is the German net-metering situation?
From the first bit of the paper it looks to me like the assumption is that feeding into the grid doesn't pay well (Ie. cost of solar is more than what you get from feeding it to the grid - and that's certainly not the case in my area)

People seem to think it's wrong to put power into batteries when you could just sell it straight to the grid, but with no battery bank, at night you are using up a lot of what you "sold" that day.

Most people look at the economics and see that you're better off using the grid as your "battery bank", since that is free..

7kWh * 365 =2555kWh a year.
If the batteries only last 6 years that's 15330kWh over the lifetime.
That's a LCOE of 19.5 cents - less than 20 cents!
That's a pretty weak LCOE, and you're still ahead by a half a cent.
Even if the battery system is $4000 and the LCOE is 26 cents, you're still paying 6 instead of 20...

Knock the LCOE down another nickel, and you're *making* 5.5 cents on the stored power- not losing a nickel by storing it for later.

So - lets say I take that path...
I pay $4k for a battery system.
And it's 15330kWh over the lifetime.
That 15.3MWh is coming from my battery now instead of from the grid. So I've avoided purchasing $.20*15330 ($3066) of power. But I've also not gotten a credit of .25 * 15330 ($3832)

Now, in my calculations, that means after 6 years I am worse off by $4766 because I bought those batteries (and the extra equipment to go with them)
(Assuming $4k is reasonable for a 145Ah, 48V pack and associated euipment. I think that's low, but haven't priced it out.)

Now, lets say you argue that getting paid $.05 more than you buy the power for is a misstatement- that really you meant that you would pay $.25 and get paid $.20.
In year 6 you are still $3234 worse off by getting batteries.

I'm ignoring interest rate (borrowing that $4k to buy the batteries -or- investing the $4k instead of buying batteries)
And
I'm ignoring the likely increases in power rates.
I believe those to both be fairly minor impacts and offset each other.


The bigger impact is if you change to a feed-in tarriff so that's about $.05/kwh (a little below cost of solar) while the purchasing price is $.31/kwh
Only when you have a price differential that large does it make sense to use a battery system that costs $4k for 15.3MWh.

{ $3k system is } a LCOE of 19.5 cents - less than 20 cents!
That's a pretty weak LCOE, and you're still ahead by a half a cent.

No - each kwh you put through a battery bank instead of the grid is costing you $.195/kwh MORE than it would have otherwise.
(really $.245/kwh because of the (presumably) day/night peak/offpeak differential you included previously.

 

[PVfarmer]

And in Texas you only pay POCO 7 cents per kWh, so it still varies from place to place.

With net metering, you generally pay the same or less for off peak power than you are paid for your on peak surplus, so selling it back is cheaper than putting it into a battery bank.
Again, it varies from place to place.

Um...SEVEN cents? Wow. But are there any "POCO pays you" rates higher than that, or is it all net metering?
Even then- if you consume 15kW a night from batteries, sure that's only $1.05 a day.
But it's 383.25 a year.
More in the range of breaking even, but having the luxury of power when the grid goes down.

What is the German net-metering situation?
From the first bit of the paper it looks to me like the assumption is that feeding into the grid doesn't pay well (Ie. cost of solar is more than what you get from feeding it to the grid - and that's certainly not the case in my area)

They're X or XX years ahead of us, it's those x's that are the important thing.
Good question, thanks- this explains a lot of it. But it's almost 2 years old so...where are we know, exactly?

THE GERMAN SOLAR MARKET: FIT FOR A CHANGE

October 12, 2013

To understand the connection between net energy metering and what’s going on right now in Germany, a little bit of history helps. In 2000, the German government launched a massive ratepayer-subsidized campaign to expand solar energy deployment—the solar feed-in tariff (FiT) program. FiTs subsidize generation from renewable energy technologies, making them affordable in the near term and enabling industry-wide growth. Since solar equipment costs were very high relative to retail electricity prices as recently as three years ago, the Germans set FiT levels well above the retail price of electricity in order for solar systems to make economic sense. This led to a flood of new investment, an unprecedented multi-year explosion in solar installations, and by consequence, large-scale reductions in PV equipment costs.


FiTs are designed to help governments meet certain capacity targets. So (like most subsidies) they slowly phase out over time by offering a lower price per kilowatt-hour (kWh) as different targets are met, resulting in a step down of FiT levels year after year. This brings us to where we are today in Germany, with the FiT for typical residential systems set at $0.20/kWh, two and a half times lower than it was in 2010.
:jawdrop:
Unlike the situation stateside where customers are credited for their solar-generated electricity at the full retail electricity rate under net energy metering, most German systems are only credited at the current FiT rate ($0.20/kWh). German residents, on the other hand, pay on average $0.36/kWh for electricity in their homes. This discrepancy is the primary reason the German solar market is in transition.
http://www.csmonitor.com/Environmen...yes-new-kind-of-net-metering-self-consumption

Most people look at the economics and see that you're better off using the grid as your "battery bank", since that is free..

I don't quite get that- once you put the power into the grid, it's gone. It comes back at a different $ rate...

So - lets say I take that path...
I pay $4k for a battery system.
And it's 15330kWh over the lifetime.
That 15.3MWh is coming from my battery now instead of from the grid. So I've avoided purchasing $.20*15330 ($3066) of power. But I've also not gotten a credit of .25 * 15330 ($3832)

This is where we differ- I'm pretty sure you have to subtract the LCOE from that 25 cents. ...you're making: (.25 - the LCOE).

(Assuming $4k is reasonable for a 145Ah, 48V pack and associated euipment. I think that's low, but haven't priced it out.)

I'd say it's a little below "average"- that would be fancy batteries and a less-fancy inverter, charge controllers aren't too much $$.
http://www.solarhome.org/schneidere...0240vac.aspx?gclid=CJ3lk4bI2MYCFUlqfgodhOEIkA

Now, lets say you argue that getting paid $.05 more than you buy the power for is a misstatement- that really you meant that you would pay $.25 and get paid $.20.
I'm ignoring interest rate (borrowing that $4k to buy the batteries -or- investing the $4k instead of buying batteries)
And
I'm ignoring the likely increases in power rates.
I believe those to both be fairly minor impacts and offset each other.
The bigger impact is if you change to a feed-in tarriff so that's about $.05/kwh (a little below cost of solar) while the purchasing price is $.31/kwh
Only when you have a price differential that large does it make sense to use a battery system that costs $4k for 15.3MWh.

I have to admit you lost me there...I mean you're paying:LCOE plus the nickel.
That's how I interpret the paper from the OP- if the LCOE plus the "nickel" is < what you would pay for power, batteries = good.

If you're paying 25 cents and getting paid 20, batteries are an even better option- like the current situation in Germany.

 

[GoldDigger]

I don't quite get that- once you put the power into the grid, it's gone. It comes back at a different $ rate...

Most states with net metering pay you exactly what they charge you. The main exception are those areas with Time Of Use (TOU) rates, which often pay you more than they charge you when you take the time factor into consideration. However many of them are starting Peak rates later in the day and keeping them in effect later, which reduces that advantage to solar PV users.
Why would you put your energy into a battery where you get back exactly what you put in when you can use the "free battery" of net metering to get back more than you put in?

PS: In Texas, if you want to get net metering you will find yourself paying 8 or more cents per kWh to a third party "wheeler" instead of the local POCO.

 

[PVfarmer]

Most states with net metering pay you exactly what they charge you. The main exception are those areas with Time Of Use (TOU) rates, which often pay you more than they charge you when you take the time factor into consideration. However many of them are starting Peak rates later in the day and keeping them in effect later, which reduces that advantage to solar PV users.

Why would you put your energy into a battery where you get back exactly what you put in when you can use the "free battery" of net metering to get back more than you put in?

PS: In Texas, if you want to get net metering you will find yourself paying 8 or more cents per kWh to a third party "wheeler" instead of the local POCO.

Ok, the first part, yep, it is different everwhere, but the POCO bumping up the rates when there's no PV output is a great reason to get batteries.

The second part- because you can conceivably spend less on panels, spend that savings on batteries, and still have the same electric bill of zero, *with* the added benefit of battery backup.
Which is also better for the grid, not that it matters to us, but this is interesting stuff. It does matter if you are trying to "look ahead"...

The third party wheeler thing...you mean devloper/installer there? Is there a state law or POCO code that requires a third party? That certainly complicates things.

For years, HECO has pointed to data showing that customer-owned solar is generating more power than average minimum daytime loads on a large number of its circuits, or even exceeding half or more of circuits’ average daily peak loads, and tying those facts to its fear that distributed solar is presenting it with a looming grid stability problem.
http://www.greentechmedia.com/artic...g-enphase-data-to-open-its-grid-to-more-solar

 

[GoldDigger]

In a non-monopoly utility market you can buy power from a party other than the one who owns the distribution lines to your home.
That third party buys power from the power generator of their choice, puts it on the grid and then you take it off at your end. That mode of power transport is called "wheeling" and involves a small fee to the owner of the lines it travels over.
Some options involve buying "green" power at a premium and other strange manipulations.
If the spot prices are lower than the contract prices the customer might even pay less that way for a short time.
The customer may also pay a connection fee to their local POCO as part of the deal.

Most analyses of the economics of time shifting power using batteries seriously underestimate the battery cost.

If you have net excess power, having a battery bank does you no good at all.
If you have net power purchase, why not pay the lower POCO price for that and avoid the batteries
Finally, with current battery technology there will be times (Absorb and Float) when the batteries and load cannot Absorb the full potential panel output. A GTI will always be able to deliver maximum panel output while a CC may not be able to accept it.
As a result, you may need more panel power with batteries, not less.

 

[ggunn]

Why would you put your energy into a battery where you get back exactly what you put in...

In theory, of course.

 

[ggunn]

It's not that simple. Every AHJ/utility has got its own policies, rates, tariffs, interconnection rules, etc. What is economically advantageous to a homeowner in one jurisdiction might not be the best choice for someone else just a few miles away.

Also, as we discussed in that other thread, you cannot just buy a bunch of batteries and connect them to a grid tied inverter. Battery inverters are different from PV inverters.

 

[K8MHZ]

The Germans know what's what.
https://pvspeicher.htw-berlin.de/wp...ttery-Systems-in-the-Self-Consumption-Age.pdf

"Mean cost" there is the sort of the same as LCOE.
The LCOE of the batteries/battery inverter, etc. is the important thing.
You have to *use* the batteries- if they're just used for backup when the grid goes down, they'll take forever to pay for themselves, maybe never.

For instance-
People seem to think it's wrong to put power into batteries when you could just sell it straight to the grid, but with no battery bank, at night you are using up a lot of what you "sold" that day.
So, say you are paying 20 cents for power, and getting paid 25 cents for what you put in.
So you're losing a nickel by not putting that power straight into the grid....BUT, the sun is free in the first place, so that 5 cents is really part of the LCOE.
What you're really paying over time with batteries is: the LCOE minus what you would have paid the grid, which should be a negative number.

LCOE = Total Life Cycle Cost / Total Lifetime Energy Production

If the battery system costs $3000, and you are using it to replace 7kWh every night...a little under 58A at 120V, or 145A at 48V(batteries/bank=400A total, 145A=27% average drain).

7kWh * 365 =2555kWh a year.
If the batteries only last 6 years that's 15330kWh over the lifetime.
That's a LCOE of 19.5 cents - less than 20 cents!
That's a pretty weak LCOE, and you're still ahead by a half a cent.
Even if the battery system is $4000 and the LCOE is 26 cents, you're still paying 6 instead of 20...

Knock the LCOE down another nickel, and you're *making* 5.5 cents on the stored power- not losing a nickel by storing it for later.

All the above is based upon the assumption that every kWh that goes into the battery will be available later for return to the system, is it not?

 

[jaggedben]

The Germans know what's what.
https://pvspeicher.htw-berlin.de/wp...ttery-Systems-in-the-Self-Consumption-Age.pdf

The graph on the first page of the link says it all with respect to Germany, and applies to just about nowhere in the US.

If the price of grid electricity is higher than the cost of PV generation, which in turn is higher than what you get paid for exporting to the grid then yes, batteries are worth it if their price per kWh of energy used is less than the grid-price minus the PV price.

That's true almost nowhere in the US because net-metering more or less by definition means that what you get paid for exporting to the grid is the same as what you get paid for importing. And the US is almost entirely net-metering and not FIT.

It's important to note that the Germans have created the graph in question very much on purpose because their government and society is prioritizing solar as means to mitigate climate change, and also for energy independence. First they created an outsized incentive (high FIT) to encourage adoption of grid-tied solar, then when that worked so well that they had too much solar, they adjusted the fit to encourage 'self-consumption' and the use of batteries.

We in the US have no such unity of purpose and you have multiple players working both to support and undermine solar and other renewables in various ways, so we are nowhere near there (yet?). Certain policy changes to net-metering could swiftly change the situation, but it's fairly pointless from a national energy strategy point of view until we have much, much more solar.

 

[PVfarmer]

Most analyses of the economics of time shifting power using batteries seriously underestimate the battery cost.

If you have net excess power, having a battery bank does you no good at all.
If you have net power purchase, why not pay the lower POCO price for that and avoid the batteries
Finally, with current battery technology there will be times (Absorb and Float) when the batteries and load cannot Absorb the full potential panel output. A GTI will always be able to deliver maximum panel output while a CC may not be able to accept it.
As a result, you may need more panel power with batteries, not less.

That wheeling thing sounds a bit weird. I'll look into that. Strangle manipulations indeed!

Yes, the cost estimates are all over the place, really.
Here's a basic number- $350 for a 6V / 300A battery, a really good AGM. So 4 of those in series you've got a 24V / 300A bank, or 60A at 120V (just loose numbers).
That's $1360, add inverter to make $4000.

If you use 25% of that 60A a night, or 15A, that's 1.8kWh a night, 657 kWh a year.
8 years = 5256kWh.
LCOE = 7.6 cents/kWh.
If you use 20% of that 60A a night (still with 8 years, probably more realistic?): LCOE = 9.5 cents.

That's less than most people pay for power!

times (Absorb and Float) when the batteries and load cannot Absorb the full potential panel output.

Not sure what you meanthere. GTI=grid tied inverter and CC= charge controller. So yes, you have to factor in efficiencies too, basically?

 

[PVfarmer]

It's not that simple. Every AHJ/utility has got its own policies, rates, tariffs, interconnection rules, etc. What is economically advantageous to a homeowner in one jurisdiction might not be the best choice for someone else just a few miles away.

Also, as we discussed in that other thread, you cannot just buy a bunch of batteries and connect them to a grid tied inverter. Battery inverters are different from PV inverters.

True, but the how much it costs overall versus how much power you get out of it is a....baseline?
It might even be different for direct neighbors- one person might not care about outages, and just want a zero bill for zero down, the next person might want to put in panels that produce 2 or 3x their usage...
It depends on trees too- someone who only has sun from not-the south for part of the day might want batteries.

And sure- you could pay between $3000 and 10,000 for a system!
Someone with an electric car might want to spend $10000- there's a whole new twist...
There's a hybrid inverter for $1049- not sure if I'd go for that one however, more like $2100+ for a "mainstream" one....or $5000 for a Sunny I...

 

[GoldDigger]

...
...

times (Absorb and Float) when the batteries and load cannot Absorb the full potential panel output.

Not sure what you meanthere. GTI=grid tied inverter and CC= charge controller. So yes, you have to factor in efficiencies too, basically?

No. It is not just a matter of efficiency.
As the SOC of the battery bank increases, the wattage that the battery can safely accept decreases. Unless you deliberately undersize the panel array, you will not be able to use the full panel power at that time. Unlike with a GTI, that potential panel power is wasted, in that it is not taken from the panels and utilized.
Note that this will not necessarily be a problem if the particular batteries, unlike lead acid, can accept close to constant current charging and can always be kept at less than full charge (Partial State Of Charge, PSOC, operation).

 

[PVfarmer]

All the above is based upon the assumption that every kWh that goes into the battery will be available later for return to the system, is it not?

The graph on the first page of the link says it all with respect to Germany, and applies to just about nowhere in the US.

If the price of grid electricity is higher than the cost of PV generation, which in turn is higher than what you get paid for exporting to the grid then yes, batteries are worth it if their price per kWh of energy used is less than the grid-price minus the PV price.

That's true almost nowhere in the US because net-metering more or less by definition means that what you get paid for exporting to the grid is the same as what you get paid for importing. And the US is almost entirely net-metering and not FIT.

It's important to note that the Germans have created the graph in question very much on purpose because their government and society is prioritizing solar as means to mitigate climate change, and also for energy independence. First they created an outsized incentive (high FIT) to encourage adoption of grid-tied solar, then when that worked so well that they had too much solar, they adjusted the fit to encourage 'self-consumption' and the use of batteries.

We in the US have no such unity of purpose and you have multiple players working both to support and undermine solar and other renewables in various ways, so we are nowhere near there (yet?). Certain policy changes to net-metering could swiftly change the situation, but it's fairly pointless from a national energy strategy point of view until we have much, much more solar.

K8-
I left out the efficiencies to simplify things.

ben-
Multiple players, uh-huh. We'll get there eventually!
Even with net metering- if you are both getting paid and paying 15 cents for power, and the LCOE of the battery system is 12 cents...
you're ahead. And you have power when there's no grid.

I bet a lot of people just say "never mind" about getting solar when they find out plain panels are no good when the grid goes down...if they are even informed of that little fact!
But the panels CAN be good, and batteries can improve them.

 

[jaggedben]

Here's a basic number- $350 for a 6V / 300A battery, a really good AGM. So 4 of those in series you've got a 24V / 300A bank, or 60A at 120V (just loose numbers).
That's $1360, add inverter to make $4000.

If you use 25% of that 60A a night, or 15A, that's 1.8kWh a night, 657 kWh a year.
8 years = 5256kWh.
LCOE = 7.6 cents/kWh.
If you use 20% of that 60A a night (still with 8 years, probably more realistic?): LCOE = 9.5 cents.

That's less than most people pay for power!

Your 9.5 cents figure is probably optimistic, but let's take it at face value...

What of the cost to charge those batteries? What's the point in paying to store energy when you could just use that energy, or energy from the grid?

Basically, the difference between what the utility charges you for importing from the grid and pays you for exporting to the grid has to be greater than that figure. Otherwise it makes more monetary sense to export the PV energy for whatever they pay you for it. This is true even if the cost of PV+batteries is less than the grid. Yes, that last sentence is correct.

Tell me where in the US that is true right now. Most net-metering policies charge you roughly the same for exports and imports. In some states where they only pay you wholesale for exports, or overproduction, it might be worth it. But I doubt that in those states PV+batteries has reached grid parity.

Batteries might have value that isn't so monetarily tangible (back up power, carbon neutrality, not having to give money to that evil utility), but I don't see how they make anybody money in most places in this country, yet.

 

[K8MHZ]

Batteries would make much more sense where the POCO doesn't offer bi-directional metering.

Otherwise, it looks like grid storage would be the way to go.

 

[PVfarmer]

No. It is not just a matter of efficiency.
As the SOC of the battery bank increases, the wattage that the battery can safely accept decreases. Unless you deliberately undersize the panel array, you will not be able to use the full panel power at that time. Unlike with a GTI, that potential panel power is wasted, in that it is not taken from the panels and utilized.
Note that this will not necessarily be a problem if the particular batteries, unlike lead acid, can accept close to constant current charging and can always be kept at less than full charge (Partial State Of Charge, PSOC, operation).

Well, the good news is, NREL / SAM does battery banks now, as of a few days ago.

Not getting full panel power isn't always a bad thing- you lose output to clipping when your DC is higher than AC, especially when the DC/AC ratio is 1.2 / 1.3 etc.
But you gain it back at off peak hours.
There are setups that would work around those losses, aren't there? Aside from pricey batteries?
Well, and pricey inverters- there are more than one that can just take whatever is needed from the AC inverter output.

Have you checked out the charge rates on the good AGM batteries? Some are quite good. (Concorde/Lifeline/Sun Xtender).

 

[PVfarmer]

Your 9.5 cents figure is probably optimistic, but let's take it at face value...

What of the cost to charge those batteries? What's the point in paying to store energy when you could just use that energy, or energy from the grid?

Basically, the difference between what the utility charges you for importing from the grid and pays you for exporting to the grid has to be greater than that figure. Otherwise it makes more monetary sense to export the PV energy for whatever they pay you for it. This is true even if the cost of PV+batteries is less than the grid. Yes, that last sentence is correct.

Tell me where in the US that is true right now. Most net-metering policies charge you roughly the same for exports and imports. In some states where they only pay you wholesale for exports, or overproduction, it might be worth it. But I doubt that in those states PV+batteries has reached grid parity.

Batteries might have value that isn't so monetarily tangible (back up power, carbon neutrality, not having to give money to that evil utility), but I don't see how they make anybody money in most places in this country, yet.

So how would you define "cost to charge"? The point in "paying" to store energy is that, when it is cheaper than what you pay the POCO, you are saving money.
Without batteries, you end up drawing as much from the grid as you put in during daylight hours.
With batteries, you put in less, but you pay less at night. Of course, we're back to all the tariffs/codes/rules etc. there.

Tell me where in the US that is true right now. Most net-metering policies charge you roughly the same for exports and imports. In some states where they only pay you wholesale for exports, or overproduction, it might be worth it

Not quite sure about all the different state policies- all 50 are pretty much different. I still think that if you're paying/getting paid 18 cents and your battery LCOE is 12 cents...you're aren't making money, but at least you are saving a higher amount.
I can't put my finger on why really, other than "the sun is free".
So say if the batteries save you the same amount that they cost in 6 years- you might get another 2 years of "free" power.
One small detail- batteries' life cycle rating is based on "they are done when they reach 80% of the original capacity", so you can...go beyond that somewhat.

 

[PVfarmer]

Batteries would make much more sense where the POCO doesn't offer bi-directional metering.

Otherwise, it looks like grid storage would be the way to go.

You lost me there.
"Doesn't offer bi-directional metering"....that means....you're off grid? Or you have two PV systems, one for output and one for backup?
I still don't get "grid storage" at all. They charge you for "buying it back". So when the price is the same in/out, you have a zero bill, but you spent more than you should have on solar panels.

Your 9.5 cents figure is probably optimistic, but let's take it at face value...

What of the cost to charge those batteries?

Arrgh!
This guy is on the right track- but WHERE is the actual equation?
And .32 is way too high, never mind .47...
I feel like I'm missing something obvious- how does he get .32 $/kWh from any of these other numbers?

As outlined above, the $/kWh figure is nowhere near sufficient to fairly contrast competing battery models and types. In order to progress the discussion further, we need to introduce a more appropriate metric, the cost of stored stored energy (COS). This is a much closer approximation to the true cost of battery storage.

COS values for the three batteries are calculated using the equation below. Note that this calculation has been simplified to assume that the battery capacity does not degrade towards 80% as the number of cycles increases – the equation can be modified to include this if required.

Summary Table​

	Cost ($)	Capacity (kWh)	$/KWhcapacity	COS ($/kWh)
Lead Acid Battery	3,100	8.2	378	0.32
Li-ion Battery 1	3,000	7	429	0.47
Li-ion Battery 2	3,500	10	350	0.32

http://www.solarchoice.net.au/blog/battery-energy-storage-cost-comparisons

Example battery specifications​

	Cost ($)	Capacity (kWh)	Cycles	DoD (%)	Round Trip Efficiency (%)	$/KWhcapacity
Lead Acid Battery	3,100	8.2	3,000	50	80	378
Li-ion Battery 1	3,000	7	2,000	50	92	429
Li-ion Battery 2	3,500	10	1,500	80	92	350