Watch Elon Musk unveil Tesla's Powerwall, a $3K battery for your home to 'change the world'


The thing on NPR this morning about this said that the expectation is that such a thing should cost 20 or 30 grand, so in comparison, that is cheap, but still out of reach of many people. But then again, so are solar panels… Aren’t they still in the 20 to 30 grand to buy and have installed?

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Depends on how much you want. Prices here are round about a couple of grand for 1.5kW up to $20,000 for a 10kW system fully installed. They’re a lot cheaper than they used to be.


If you were to sign up with Solar City that cost would be spread out over a 10 year period I believe. But still, even without solar panels it is a fairly killer deal if someone lives in an area with peak power pricing.
Below isn’t aimed at you @Mindysan33

I’m getting really tired of people claiming it isn’t enough. We need to do something other than hope something better will come along. We start now, or we wait for Earth to become inhabitable and we become extinct.


I’ve been researching this a bit this morning, though I am by no means an expert. The specs I found suggest that a typical U.S. household could use these to go off the grid for about $9-$12k in batteries and about $15-$20k in solar. Expensive, but the batteries are much cheaper an existing batteries, and they are Li instead of lead-acid which most are these days. At those prices, the payoff is pretty long, like as long as the warranty. But for some the idea of going off the grid is going to be worth the cost, and for others it will be the only option. The backup battery at $3500 is an interesting device, and something I’d actually consider since I probably can’t really go OTG in my BK apt.


Random thought. A natural gas (or propane) fed to a small turbine (are there model aircraft gas-burning jet engines?), connected to a small model-aircraft motor. These motors can work as generators, and can easily reach over a kilowatt, in a very compact form factor.

Another random thought. What about using cells with way higher peak power output? Charge slowly, use for short-term high-power demand (resistive welding comes to mind, or feeding a pulsed power device)?

92% roundtrip DC efficiency

Is anyone else worried about this number? Wouldn’t that effectively crush anyone’s “off peak pricing” grid charging plans?

  • How long do the batteries last?
  • How many kilowatt hours does it take to manufacture a battery?
  • What area of land would need to be covered with solar panels to power a Gigafactory?

You need the Tesla Capacitor Bank for that

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I was looking at it from the other direction. $3k is about 2 years of my current power bill, and Powerwall won’t make that bill any smaller. Very very hard to prove it in, on sheer finance.

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Might be a little out of date now, but…
Concentrating solar power in deserts delivers an average power per unit land area of roughly 15 W/m2. So, allowing no space for anything else in such a square, the power delivered would be 150 GW. This is not the same as current world power consumption.
It’s not even near current world electricity consumption, which is 2000 GW. World power consumption today is 15 000 GW. So the correct statement about power from the Sahara is that today’s consumption could be provided by a 1000 km by 1000 km square in the desert, completely filled with concentrating solar power. That’s four times the area of the UK. And if we are interested in living in an equitable world, we should presumably aim to supply more than today’s consumption. To supply every person in the world with an average European’s power consumption (125 kWh/d), the area required would be two 1000 km by 1000 km squares in the desert.


I can get one for our house for a total outlay of under 10K because of our very mild climate and lots of sunny days (coastal Southern CA), but I don’t know how long we’ll be in this house so the ROI isn’t that great yet. And a lease can be tricky if you are going to sell the house as well…

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Maybe a very good thing in developing countries, if people can afford the thing. But there will be nasty likely unintended consequences in developed countries: to many people in the US “off the grid” means out in the middle of nowhere, or at least outside of town/city and far enough away from utilities to make this pencil as an alternative.

Cutting the cost of moving out into the middle of nowhere will increase transportation energy use commuting to said places, increase habitat destruction, increase the costs to fight wildland fires that will threaten the homes, and more. We need more people living in cities, not fewer, and it’s hard for me to see this development as actually good news.

I live in a city.
It sucks.


This is good news for non-off-the-grid people for two reasons:

Resilience. A house, or even an apartment buildin, which has a tidy way to keep the power on – even a reduced amount enough to run the refrigerators, emergency lights, water pumpts, a battery charger and the like – will remain habitable in times of crisis.

Distributed grid capacity levelling: Houses with solar panels can even now contribute excess capacity to the local grid. In the future, a smart grid could take advantage of power stored in household batteries. Instead of firing up gas generators or buying power from another state / region, a utility could put out a request for juice from home systems in times of need.

Just a little stored excess power could greatly reduce blackouts by preventing cascading collapses.

Of course, prices will come down before these uses are viable. But they will come down in price.


I’m not sure batteries are the best tech for this. By gut feeling I’d go for hydrogen fuel cells with electrolyzers. But apparently the membranes aren’t up to the job yet. Another possibility is supercapacitors, due to their lifetime; these would be more friendly to frequent charge/discharge cycles, but tend to be quite bigger, and the ionic fluids that make them tick better than aqueous electrolytes are still a bit overpriced.

So now we’re stuck with batteries and their limited cycles. Hope not for long…

On a side note, we can avoid part of the losses in the output power; computers and essentially anything that runs on a switching power supply can run from DC, and from a quite wide range of voltages. If you have a 120 volt car battery, you can likely hook it directly to a computer’s input and it should happily start.

…don’t do it with ordinary transformers or with lights that need a magnetic ballast. This may result in interesting audiovisual and olfactory effects.


What a terrible presenter. He was much better on The Simpsons.


With time, I expect there might be layers of backup, using “all of the above,” perhaps including flywheels. Batteries for the first few minutes, banks of fuel cells acting in the role that natural-gas power plants are used in now.

The as-big challenge will be reworking the grid to allow smart two-way traffic. Maybe we’ll have to wait for a solar flare to fry half of the grid first . . .

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The solar flares won’t fry a grid that’s prepared for that. The mechanism is saturating the transformer cores with induced DC current, and that’s easy-ish to defend against (switch off the transformer when it starts overheating (and possibly cause a cascade blackout), or run it at below 90% load to have reserve. Short-haul lines aren’t susceptible, long-haul ones will hopefully be replaced with HVDC in time.

I see the chance rather in “energy auctions”; smart grid, knowing the supply forecast for next seconds to hours, adjusting energy prices per minute. So the freezer knows that there is abundance of cheap power just now, and it can afford to store the energy now, and sink the excess wind power flowing in. Or the batteries can play the role of a market speculator, charging when the power is abundant and discharging back to the grid for a markup when there is a shortage. Similarly, said freezer knows it can go from say -18 to -14 'C safely if the energy is overpriced at the moment, or decide that instead of risking a $500 groceries load it will play it safe and buy the more expensive power to be sure instead of waiting. The consumer then can select appropriate strategy for the household or device.