May 4, 2015

YOUR NEXT HOUSE WILL BE A VOLT:

Tesla Battery Economics: On the Path to Disruption (Ramez Naam, 5/04/15, Gizmodo)

Here are two ways we can calculate the LCOE of the Tesla Powerwall.

1. Rule of Thumb: 1,000 Full Charge Cycles. This gives an LCOE of $0.35 / kwh. That compares to average grid electricity prices in the US of 12 cents / kwh, and peak California prices on a time-of-use plan of around 28 cents / kwh.

2. 10 Year Warranty + Daily Shallow Cycles. Tesla is offering a ten-year warranty on these batteries, which is bold. Yet evidence shows that Tesla automotive batteries are doing quite well, not losing capacity fast. Why? It's because they're rarely fully discharged. Most people drive well under half of the range of the battery per day. So let's assume 10 years of daily use (3650 days, if we ignore leap days) and 50% depth of discharge on each day. Using the 7kwh battery, that gives us a price of around 23-24 cents / kwh.

Both of those prices are the price to installers. It's not counting the installer's profit margin or their cost of labor or any equipment needed to connect it to the house. So realistically the costs will be higher.

Tentative Conclusion: The battery isn't quite cheap enough for most in the US to buy on a purely cost-benefit basis, yet. Unless outages are extremely expensive.

Outside the continental US, the batteries economics look far better, though. 43 US states have Net Metering laws that compensate solar homes for excess power created during the day.

In some of the sunniest places in the world, though, retail electricity prices from the grid are substantially higher than the US, plenty of sunlight is available, and Net Metering either doesn't exist or is being severely curtailed. [...]

The real prize, though, would be India. Northern India is sunny. The power grid struggles to provide enough electricity to meet the daytime and early evening peak. India is now rolling out Time-of-Day pricing to residential customers and reports indicate that retail peak power prices are edging towards 20 cents / kwh in some cities. (Most commercial customers in India are already on Time-of-Day pricing.) For now, the solar + battery economics aren't quite there for Indians that have access to the grid, though with outages there so frequent, high-income urbanites and commercial power users may find that the reliability value puts it over the top.

For most of the US, this battery isn't quite cheap enough. But it's in the right ballpark. And that means a lot. Net Metering plans in the US are filling up. California's may be full by the end of 2016 or 2017, modulo additional legal changes. That would severely impact the economics of solar. But another factor of 2 price reduction in storage would make it cheap enough that, as Net Metering plans fill up or are reduced around the country, the battery would allow solar owners to save power for the evening or night-time hours in a cost effective way.

That is also a policy tool in debates with utilities. If they see Net Metering reductions as a tool to slow rooftop solar, they'll be forced to confront the fact that solar owners with cheap batteries are less dependent on Net Metering.

That same factor of 2 price reduction would also make batteries effective for day-night electricity cost arbitrage, wherein customers fill up the battery with cheap grid power at night, and use stored battery power instead of the grid during the day. In California, where there's a 19 cent gap between middle of the night power and peak-of-day power, those economics look very attractive.

And the cost of batteries is plunging fast. Tesla will get that 2x price reduction within 3-5 years, if not faster.

Posted by at May 4, 2015 8:45 PM
  

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