Published on 5 October 2020 |
by Zachary Shahan
5 October 2020 by Zachary Shahan
We just pulled an article about vanadium versus lithium-ion batteries for long-term energy storage because Tesla CEO Elon Musk replied: “This article is completely inaccurate about the cost. current lithium batteries by a factor of 5 or more & 10 times longer than their term. “However, that raises more questions than answers to me, so I dug deeper and have some information. new to share along with many other contexts related to battery prices and long-term costs.
I have received some additional details from Elon about Tesla’s energy storage prices, including information that I do not think has been made public before, and I have reached out to StorEn Technologies for more details on their assumptions.
First of all, however, there are at least a few things to point out here to clear up some of the major confusion and misunderstandings. To begin with, the most important things are:
The dollar / kWh cost of an electric vehicle battery is not exactly the same as the dollar / kWh cost of a fixed battery storage system.
Also, there are actually two different types of dollars / kWh – there is a storage system’s price based on its one-time energy storage capacity and upfront cost (for example, if your battery has storage capacity. 100 kWh of energy and is priced at $ 5,000, the figure is $ 50 / kW), and yes reality price per kWh of Electricity is stored for the lifetime of the storage system. To figure out the latter, you need to calculate the number of cycles and the life of the system (and in fact, even more than that, like efficiency, maintenance and repair). I did this for the Tesla Powerwall compared to other top options back in 2015 when Powerwall launched – check out if you want to dig deeper into what such computations entail.
The price estimates in today’s earlier article that Elon responded to are as follows: “Lithium batteries typically cost between $ 600 and $ 900 / kWh and last for 3,000 to 4,000 cycles. Thus, their cost per cycle averages $ 0.21. ”
Anyone who follows the electric vehicle market, especially the EV battery price, can certainly look at the first set of numbers (600–900 USD / kWh) and eyes bulging out of his head. However, this is not the price for Li-ion batteries for electric vehicles. This is the price for stationary storage, much different. Also, I’m pretty confident that this is an “all-round” price – pricing for a full static storage system, not just cells or battery packs.
With all of that in mind, let’s dig a little deeper.
Tesla Powerpack & Megapack pricing
One commentator pointed out that the Tesla Powerpack price is currently at $ 539 / kWh. That’s after the recent drop and is still close to $ 600 / kWh. It’s certainly not a 5x difference, but it’s a lot lower than the $ 750 / kWh average that was used to give an estimate of $ 0.21 per cycle. Yes, that $ 539 / kWh price includes inverter costs, but I believe that StorEn is really focused on the whole system cost, especially since vanadium series batteries benefit more from that point of view – This is related to the great benefit that I will come back to in a very long, very long moment.
In response to my question about the cost of Tesla Powerpack, Elon Musk provided some interesting new information:
“Powerpack is an old product. Megapack is something we currently deliver to utility or heavy industry users.
“Its battery portion is less than $ 200 / kWh. Electronic equipment and maintenance for 15 to 20 years cost up to about $ 300 / kWh. However, it would be inaccurate to just compare the cost of vanadium series batteries with the costs of lithium batteries plus the capacity electronics and the 15 to 20 years of maintenance time.
Again, as I read it, StorEn is referring to the total, system-wide cost. One of the benefits of the vanadium battery is that it is said to require very little maintenance and repair, so of course, StorEn would be more interested in comparing system-wide costs. I have reached out for clarification and will update this post to indicate if it is true if I get a response on this issue.
Also, again, you should really consider the lifetime cost per kWh stored. As you can see above, Elon has recorded 15–20 years of service. StorEn refers to a 25 year lifespan on a 500 kWh system with a maximum of 15,000 cycles. What does that mean in terms of long term cost per kWh of storage? Well, we don’t have that info because I don’t see the price for the ST 50-500 system. However, maybe we have it with a bit of math. In another article, StorEn notes that the line vanadium batteries can cost $ 0.04 / kWh per cycle and can reach 15,000 cycles. That goes up to $ 600 / kWh. (Interestingly, that’s the last point in StorEn’s estimate for Li-ion batteries.)
If I can get more details on pricing from StorEn, I will update this post to add it or I will write a new one. Then I could also try calculating the lifetime price-per-kWh range for the Tesla Megapack.
Tesla Powerwall Specifications & Pricing
StorEn offers small scale residential / energy storage products as well as the utility scale energy storage systems mentioned above. So let’s also consider the Tesla Powerwall, a home energy storage battery that one of our writers has. (Well, he has two of them.)
A 13.5 kWh Tesla Powerwall costs $ 6,500 – our writer, Kyle Field, doesn’t cover the Tesla Gateway or installation costs. That means costs $ 481.48 / kWh. However, the price seems to have gone up a bit lately and is now $ 7,000, excluding Gate and installation (which costs $ 4,500 or $ 3,500 if it came with the top solar system Tesla roof). At $ 7,000, that’s $ 518.52 / kWh. Again, this is much lower than the low-end assumption of $ 600 / kWh (not including $ 750 / kWh or the high-end assumption of $ 900 / kWh), but it’s not equal to 1/5. cost. I am not sure if Gateway’s costing is justified, especially since it is unclear what I should compare these products and figures to.
I do not see the price of the StorEn VFB battery, but also asked the company for supply.
There are other notable specs and promises to be considered as well. StorEn batteries are rated for 25 years, while Tesla’s Powerwall comes with a 10-year warranty.
StorEn reports a life cycle of 15,000 cycles. Tesla Powerwall 1 provides ~ 5,000 lifecycle. The Powerwall 2 comes with “unlimited cycles” for solar self consumption / backup or “37.8 MWh total throughput” for other applications. Previous calculations reached a maximum of about 3,100 cycles over 10 years, while the latter calculations were 3,200 cycles if you assume 37.8 MWh referring to both charge and discharge.
As one of the final set of specifications to consider, Tesla’s Powerwall has 90% round-trip efficiency, while the StorEn system has a 75–80% round-trip efficiency.
Determining the actual cost per kWh of electricity stored over a product’s lifetime is almost within our reach. If I know a few more details, I will update this section or even publish a brand new article.
There are still some gaps here that will help provide a more thorough comparison of these energy storage systems, but here are some core conclusions:
- The Tesla Megapack is currently priced at <$ 200 / kWh, or ~ $ 300 / kWh with power electronics and bundled service, as commented by Elon Musk for me today.
- This is much lower than the recent low price of $ 539 / kWh for the Tesla Powerpack.
- A Tesla Powerwall is currently priced at $ 518.52 / kWh, up from $ 481.48 / kWh earlier this year, but that doesn’t include the cost of installing or the Tesla gate.
None of that tells us the cost of electricity stored over the lifetime of the system. To determine that, you have to add a number of other factors, some of which have been difficult assumptions to be made over a decade or two. These include efficiency, discharge depth, number of cycles, and maintenance and repair costs.
Hopefully this clears up – to some extent – the mild debate from earlier today. If I gather enough additional information on these topics, I will follow another section.
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