Re: THE Battery Technology Thread pt 3 (merged)
Posted: Wed 04 Jan 2017, 18:17:52
Actually that's what you just did. You only counted the purchase price of storing the energy not the cost of the energy delivered. That $470 was just the cost for 1 kWh of batteries. It doesn't even include the cost of the electricity.baha wrote:You're counting the purchase price of capacity not energy delivered. That $470 investment returns 3650 kw hrs over 10 years.
Top Ten Facts about Tesla’s $350/kWh (DC) PowerWall battery5. Cutting the grid connection will cost two or three times more than you think
2 kW should cover the average 1.2 kW electricity usage of the average American house, but 3.3 kW peak power will not be enough if you have many devices in a large American house, all running at once, and you want to disconnect entirely from the grid.
In fact, a SolarCity VP admitted that a single PowerWall is not enough to disconnect entirely from the grid, as 7 kWh doesn’t really offer enough power to cover all non-daylight hours: “it would require multiple units to take someone off the grid.”
Elon Musk noted in the 2015Q1 earnings call that it does not make economic sense to go off-grid, with PowerWalls.
6. The all-in price is twice the $350/kWh ‘wow’ number, but still impressive
the $3,000 or $3,500 cost is for the DC system only – be careful to compare apples to apples when looking at other products. For example, the inverter will add around $1,000 to $2,000 to the cost of the device.
As another real-world point, SolarCity is quoting $7,140 to add the PowerWall to a solar installation (includes inverter, maintenance contract, installation, control system). This doesn’t sound unreasonable, and again $700/kWh for a small home-scale system is very cheap, though as mentioned above, multiple PowerWalls may be needed for many customers.
7. The PowerWall does not let you make money on arbitrage, and Tesla knows it.
Tesla executives confirmed that the economics don’t work in America, and here’s why. As a residential owner, in the best case you’ll make 36 cents/kWh selling to the grid at peak hours, and buy at 10 cents/kWh at night. Once you include round-trip efficiency losses, that’s about $1.66 gross profit per 7 kWh (DC) cycle.
So revenue is $1.66 x 183 days x 10 years = $3,000. You’ll just about recoup the cost of the product, but you won’t profit because of two factors – the cost of inverter and installation, and the time value of money. We’re in a low-interest environment, but setting aside $7,000 today to make back $3,000 over 10 years still leaves you down $4,000 – not a very good deal.