the silliness of tesla\'s 7kwh powerwall battery
Edit note, May 6: an \"update\" section has been added to this article since the original publication]
Earlier this week, I wrote here an article entitled \"The stupidity of Tesla 10 KW --
Up Battery \", unless you install a lot of batteries for $7140 per unit, it will completely cancel its utility.
In this post, I will do the same for Tesla (NASDAQ:TSLA)
New 7kWh batteries designed for daily use.
A typical American family in 2-
3 KW in the case of not using the central air conditioner or not charging the electric car, the central air conditioner will increase by 3 extra. 5 to 5kW.
Now let\'s do some simple math: first assume
You need to use these batteries for 15 hours a day (
When the sun is not very bright or not very brightexistent).
Next, let\'s assume that during these times you need to steadily pull out 6kw to run your central air conditioner and use your other devices without worrying about it. (
Forgot to charge your electric car. )
Finally, let\'s assume that the alternative to using the battery is to pay.
Using the above figure, you will need to pay 15 hours x 6kw x if you purchase electricity from the power company.
15 hours x 365 days = $4928/year.
Now let\'s take a look at Tesla\'s alternative: each 7kw battery can only consume 2kw stably, which means that the house being discussed needs to run three of them at the same time.
Also, in the case of stable 2kw consumption plus occasional surge, each battery can only last about three hours, so in the 15 hour coverage you need five groups of three
You will never put it in the garage anyway).
The cost per battery is $3000, and the rule of thumb is that the cost of installation and inverter is twice that cost, which means that if installed separately, the cost per battery is about $6000, but you don\'t need an inverter if you are using an existing solar system, so we will use the installation price of $4000 per inverter.
So there\'s an alternative here: a)an up-
Minus the federal tax credit, the upfront cost of installing 15 Tesla batteries is $60,000.
30% of the credit was cut to 10% at the end of 2016, so the deduction of $6000 reduced the price to $54,000, orb)
Pay $4928 a year to the power company, but by earning $ 3% a year, you don\'t have to spend $54,000 in advance, and you can reduce the cost to $3308 a year.
Under these assumptions, there is a 16-
The annual return of the battery, but the battery is only 10-
One year warranty, the charging cycle may be stopped shortly thereafter, so there is no economic point in buying it.
So I look forward to Sun City (SCTY)
Instead, these are provided on nine or ten batteries
The lease of the year, as it relates (
Completely inadequate)10kWh back-
For 9 years, the time per battery has been paid $5000, but if so, I expect math to be very similar to what I outlined above (
About $4000 per battery without an inverter)
, Due to the expected ten-year lifespan.
In other words, assuming my numbers are almost correct, Tesla\'s 7kWh battery is as stupid as its 10kWh battery.
But there is a bigger problem: according to Tesla, you can only connect 9 7kWh batteries together, which means that except in the dead of night, everyone is asleep if you use these batteries, you won\'t be able to replicate the normal experience of plugging into the utility.
So, leaving aside all the stock hype, the bottom line for Tesla batteries is \"more expensive\" and \"much less utility \"(No pun intended).
Update: Due to the original release of this story, I have received a lot of feedback claiming that the 6kw power consumption I have estimated each year is too high, which may be correct because in most parts of the USS. air-
Air conditioning is used only for part of the year.
This actually reinforces my case a lot because people need to design (
A person\'s battery capacity in the \"peak load month\", even if it is only partially used for the rest of the year. So let\'s re-
Run the numbers accordingly. . .
Let\'s assume that it takes only two months for the house to smoke 6kw (July and August)
5 kw for two months (
June and September)
Then the remaining eight months are only 2kw (
Central air conditioning-
Fully off air conditioning).
In this case, the utility\'s electricity bill is: a)
62 days x 15 hours x 6kw x.
15/kWh = $837, plusb)
60 days x 15 hours x 5kw x.
Month/degree = $675, plusc)
243 days x 15 hours x 2kw x.
Therefore, 15/kWh = $1094, the total annual electricity bill will be only $837 + $675 + $1094 = $2606, minus the interest of $1620/year, $ 3% is $54,000 that is not used for battery packs = the cost per year is only $986. $54,000 up-
On the front of the battery, extend the battery payback period to nearly 55 years, which may be 5 times the battery life!
Disclosure: The author is short TSLA.
The author wrote this article himself and expressed his views.
The author was not compensated (
In addition to Seeking Alpha).
The author has no business relationship with any company mentioned in this article.