Published on 5 October 2020 |
by Zachary Shahan
5 October 2020 of Zachary Shahan
We just pulled down an article about vanadium batteries versus lithium-ion batteries for long-life energy storage because Tesla CEO Elon Musk replied, “This article is completely wrong about the cost of a lithium battery. factor 5 or more currently and 1
I got some extra details from Elon regarding Tesla energy storage pricing, including information that I don’t think was public previously, and I contacted 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 a great confusion and misunderstanding. To begin with, the most important thing is:
The $ / kWh cost of electric vehicle batteries is not at all equal to the $ / kWh cost of stationary battery storage systems.
Furthermore, there are actually two different types of $ / kWh: there is the price of the storage system based on the one-time energy storage capacity and the initial cost (for example, if your battery has 100 kWh of capacity of energy storage and costs $ 5,000, the figure is $ 50 / kW), and there it is actual cost per kWh of electricity stored for the entire life of a storage system. To understand the latter, it is necessary to calculate the number of cycles and the life of the system (and, in fact, even more, such as efficiency, maintenance and repair). I did this for the Tesla Powerwall compared to other better options in 2015 when the Powerwall came out – check it out if you want to dive deeper into what those calculations entail.
The price estimate in today’s article that Elon was responding to was as follows: “Lithium batteries typically cost $ 600 to $ 900 / kWh and last 3,000 to 4,000 cycles. Therefore, their cost per cycle averages $ 0.21 “.
Anyone following the electric vehicle market, especially EV battery prices, could definitely be looking at the first set of figures ($ 600–900 / kWh) and have their eyes bulging their heads. However, this is not a price for lithium-ion batteries for electric vehicles. This is the price for fixed storage, which is very different. Also, I’m pretty confident this was an “all-in” price: price for a complete fixed storage system, not just the battery cells or the packs alone.
With all of this in mind, let’s dig deeper.
Tesla Powerpack and Megapack prices
One commentator pointed out that Tesla Powerpack’s price is now at $ 539 / kWh. This is after a very recent price cut and is still close to $ 600 / kWh. That’s certainly not a 5-fold difference, but it’s well below the $ 750 / kWh average used to get the estimate of $ 0.21 per cycle. Yes, the $ 539 / kWh price includes inverter costs, but I believe StorEn has actually focused on the costs of the whole system as well, especially since vanadium batteries benefit the most from that point of view, which is related to a great advantage that I will be back in a moment, very long life.
In response to my questions about the cost of a Tesla Powerpack, Elon Musk provided some interesting new information:
“Powerpack is an older product. Megapack is what we now ship to heavy industrial or utility users.
“The battery pack part is less than $ 200 / kWh. Power electronics and 15 to 20 year maintenance bring the price down to around $ 300 / kWh. However, it would not be accurate to compare the cost of a vanadium battery alone with the cost of the lithium battery plus power electronics and 15 to 20 years of maintenance. “
Again, as I read it, StorEn was referring to the all-in costs, of the whole system. I have contacted for clarification and will update this article to indicate whether or not it is correct if I get a response on the matter.
Also, once again, you should really consider the total cost of living per kWh stored. As you can see above, Elon has noticed 15-20 years of maintenance. StorEn mentions a life span of 25 years on a 500 kWh system with up to 15,000 cycles. What does this mean in terms of long-term cost per kWh stored? Well, we don’t have this information as I don’t see a price for the ST 50-500 system. However, maybe we have it with a little math. In the other article, StorEn noted that vanadium batteries could cost $ 0.04 / kWh per cycle and could reach 15,000 cycles. This comes in at $ 600 / kWh. (Interestingly, this is the lower part of StorEn’s estimate for lithium-ion batteries.)
If I can get more pricing details from StorEn, I will update this article to add it or write a new one. I could also try to calculate a lifetime price per kWh range for the Tesla Megapack.
Tesla Powerwall specifications and pricing
StorEn offers a residential / small scale energy storage product as well as the industrial scale energy storage system 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.)
A 13.5 kWh Tesla Powerwall cost our writer, Kyle Field, $ 6,500, not including the Tesla Gateway or installation costs. This means a cost of $ 481.48 / kWh. The price has apparently gone up a bit recently, however, and is now $ 7,000, not including the Gateway and installation (which costs $ 4,500 or $ 3,500 when included with a Tesla rooftop solar system). With a price tag of $ 7,000, that means $ 518.52 / kWh. Again, it’s well below a low-end guess of $ 600 / kWh (not to mention $ 750 / kWh or a high-end guess of $ 900 / kWh), but it’s not a fifth of the cost. I’m not sure if it makes sense to add the gateway cost or not, especially since it’s not at all clear what I should compare these products and figures to.
I don’t see the prices for the StorEn VFB battery, but I also asked the company to provide them.
There are also other noteworthy specs and promises to consider. The StorEn battery has a nominal life of 25 years, while Tesla’s Powerwall has a 10-year warranty.
StorEn reports a life of 15,000 cycles. The Tesla Powerwall 1 offered a life of ~ 5,000 cycles. The Powerwall 2 ships with “unlimited cycles” for self-consumption / solar backup or “37.8 MWh of aggregate throughput” for other applications. The calculations of the former reach a maximum of about 3,100 cycles in 10 years, while the calculations of the latter reach 3,200 cycles if it is assumed that 37.8 MWh refer to both charge and discharge.
As a final set of specs to consider, Tesla’s Powerwall has 90% round-trip efficiency, while the StorEn system has 75-80% round-trip efficiency.
Determining the actual cost per kWh of stored electricity over the product’s lifecycle is almost at hand. If I get a few more details, I will update this section or publish a completely new article as well.
There are still some information gaps that could help provide a more in-depth comparison of these energy storage systems, but here are some key conclusions:
- The Tesla Megapack now costs <$ 200 / kWh, or ~ $ 300 / kWh with power electronics and assistance included, according to comments from Elon Musk today.
- This is well below what recently appeared to be a new low price of $ 539 / kWh for the Tesla Powerpack.
- A Tesla Powerwall now costs $ 518.52 / kWh, up from $ 481.48 / kWh earlier this year, but that doesn’t include the cost of the Tesla Gateway or installation.
None of this tells us the cost of stored electricity over the life of the system. To determine this, you need to add many other factors, some of which are difficult assumptions to formulate over the course of a decade or two. They include efficiency, depth of discharge, number of cycles and maintenance and repair costs.
Hopefully, this clears up today’s mild controversy to some extent. If you gather enough extra information on these topics, another one will follow.
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