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Comment by IpV8 | Hacker News Reader

You're going to be closer to $10,000 for that kind of storage. Probably not economical for your use case unless you get good rebates and electricity is expensive where you live.

Source: I build home battery backup systems for a living.

The types of people buying batteries today live in places where arbitrage is an option (california, hawaii), or where the grid is frequently or always down (puerto rico)... or rich people who want to be energy independent. They generally haven't made it to the general public yet, but cost is coming down every year and utilities/incentive programs are spreading.

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My parents live in a well-to-do suburb of Chicago. After the frequent, repeated power outages in recent years, a battery pack would be considered as an alternative to a generator.

They don't have a generator -- their property does not make one convenient, and they don't currently have medical needs that require constant power.

But when the power goes out in their neighborhood, just walk outside after a few minutes and listen to all the generators.

A lot of U.S. infrastructure is no longer really being adequately maintained. I expect quite a few battery packs will be sold to scenarios like theirs. As long as the power failures don't come to exceed the batteries' power delivery capabilities.

$10,000 is ~ 50kwh of battery power, that's vastly more than most people are using over a few hours.

As of yet there is nowhere in the world where the installed cost of a 50 kWh hour battery system is only $10,000. I don't think you can even get that much storage for that little money even if you're qualified to install it yourself and are just paying for the hardware. Are you perhaps just looking at wholesale cell costs?

I don't think there is any reason for a home use to install a battery pack without solar power, and with solar power they already need an inverter.

https://www.alibaba.com/product-detail/25kwh-48v-LiFePo4-bat...

Now this is Alibaba so we are talking about dubious quality still it's showing 2,000$ for 25kwh battery pack when buying 2 or more. 50kwh is 2 so that's 4,000$. That's for Lithium iron phosphate battery which should give ~2,000 cycles though they say 3,500.

PS: Grid scale you would want to install the batteries at the solar power plant so again no need for an extra inverter.

<$100/kwh for LiFePo4? That seems really hard to believe.

If that's not a scam or something that fails in 2 years, it's pretty amazing. At a lifetime of 3500 full-depth cycles it works out to a lifetime capital cost of only 2.2 cents per kWh. In sunny regions, with instantaneous solar generating costs already below 2.5 cents/kWh, it means that you can supply power around the clock at costs lower than fossil combustion.

In a March 2018 report, BNEF put 2017 utility-scale battery costs at $209/kWh:

https://about.bnef.com/blog/tumbling-costs-wind-solar-batter...

And that report was already taking into account global supply chains. That's why I am skeptical about the low Alibaba price. If EPCs can get reliable battery packs at $78/kWh (sans inverter) just by ordering from China, I would expect utility scale battery installation rates to soon go from "brisk" to "breakneck."

I was speccing to the 10-15 kwh range. Maybe you can get it for cheaper, but with the use case he described you're talking about a substantial continuous rated power and surge power. How many amps can your $10,000 50 kwh battery push? Also I'm including installation, warranty, etc. It would honestly probably be more than that because he'd likely need a more expensive inverter or 2 inverters to deal with that kind of load (I doubt his AC unit and dryer are DC).

His AC unit and dryer may actually be DC, just internally. Modern AC compressor motors are now moving to inverter drive, so incoming alternating current gets turned into DC for the inverter, washers/driers do something similar for the motor. Heating elements are just a resistor, so could run from DC. If I were putting together a system for myself those are the things I would consider, and find ways not to duplicate power inverters throughout the system.

Perhaps that includes labor and permits, not insignificant costs

Do you believe the batteries should be subsidized instead of the power going back into the grid?

Not sure why that's an either or?

Do you believe the batteries should be subsidized - Yes, I think that they should be subsidized now. I normally don't like government involvement in markets other than protecting against externalities, but in this case I believe that subsidies can expedite innovation in the area. Once the market exists and the technology moves far enough along, I think that we will be able to slowly remove the subsidies and battery systems will be cheap enough to warrant their place in the market without. Also I strongly believe that the faster we move away from fossil fuels, the less lives will be lost to climate change.

instead of the power going back into the grid - Not sure what you mean here. People sell back to the grid all the time. A battery backup system in sell mode is essentially another power plant. Great!

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