If I wasn’t clear: 3 percent of gdp is the ballpark perpetual capital cost with present technology and a 20 year storage system life. Just capital costs and just storage. Versus all of energy being roughly 5pc of global GDP now.

That is assuming we can hit that scale in the next couple decades and that nothing happens to push up costs with increased scale. More likely is a moderate cost increase, but who knows? Putting all our eggs in the battery storage basket is not great.

Just a few percent more stable base generation in the mix would greatly reduce the amount of storage needed and open more options (e.g making power to gas more reasonable)

It may be cheaper overall; it may not be. But even if you think this is modestly costlier, reducing risk and volatility of outcomes is something that one often chooses to pay for.

I find this hard to believe. Let's math it. Let's put grid storage at $200k/MWh, or about 4x current battery prices. Let's keep it at that level for sake of argument. Let's very pessimistically say we need to replace 50% of storage every decade, and again for sake of argument let's say replacing the batteries costs the whole 4x (eg. no reuse of material or converters or grid connections). So the math there gives $1T/y for storage.

Idk, it seems like even pretty pessimistic arguments with frozen costs and early retirements suggest this is cheaper than the numbers you gave.

> That is assuming we can hit that scale in the next couple decades and that nothing happens to push up costs with increased scale.

This strikes me as odd to posit about a technology that has had a steady 23% cost reduction per doubling over the last 6 decimal orders of magnitude.

Current prices of installed systems at peak scale are 150-350k/MWh.

Replacing it all on a 20 year cadence seems like a reasonable assumption.

Arguments assuming a positive return to scale 4 orders of magnitude out may be true— or may be unduly optimistic. I don’t like to have too much faith extending the lines too far off the right of the graph. When that is required, I want whatever margin and ways to reduce risk as possible: which is why I would like more nuclear in the mix. A grid with 12pc nuclear and the rest renewable (so about 3-4pc of nameplate power nuclear) would require much less over provisioning and storage.

You don't have to go all the way to battery prices scaling to 5% of the price they are today to consider it likely the price continues to fall at all.

Replacing the whole system every 20 years still seems really wild to me, especially in worlds where price doesn't fall past the cost of maintenance, because the only wear part is the battery, and batteries are modular. We could, sure, I just showed the cost is a fraction of today's energy spend, it just seems really weird not to do something smarter instead.

> Replacing the whole system every 20 years still seems really wild to me, especially in worlds where price doesn't fall past the cost of maintenance, because the only wear part is the battery, and batteries are modular.

It may be pessimistic. At the same time, you amortize things based on history.

Things like substations are amortized over 30-40 years. Battery banks don't have the history; a 20 year timeframe seems like a reasonable amortization time. Indeed, if technology improves and costs reduce like people are advocating for here, it'll be thrown away and replaced. If it wears out in ways that don't justify refurbishment, same. And refurbishment/recycling/etc are not well understood processes at scale, yet, nor are future usage patterns well enough understood to know if we will have those resources at the right places.

Again, we could get lucky: batteries could last longer than expected; we could use technologies that are close enough cousins and have a really good time at refurbishment; we could not hit any kind of scaling limitations with battery storage; etc. I agree battery storage is great. And I agree it could be sufficient alone (well, combined with other storage options) if we hit the top third of possible scenarios.

I just am concerned about the other scenarios. I can't rule them out. And if we're going to have insurance against them, it's time to buy it now.

I'd much rather face a future where people say that we wasted a few tens of billions on nuclear power plants than to face a future where people shake their head that we wasted the opportunity to save the climate by foregoing nuclear.

I'm not really following. You said, "I don’t think we can scale up storage enough at any reasonable cost." We checked the math. The math said that even with pessimistic numbers, that assume no cost improvement and that everything deprecates as fast as the batteries, the amount of storage needed was readily affordable. You agree that there's a reasonable chance the price could go down, and agree that parts other than the battery chemistry do indeed last much longer.

Isn't that the whole debate? What are we arguing about at this point?

> the amount of storage needed was readily affordable.

I'm sorry, I don't think that cost is readily affordable!

> You agree that there's a reasonable chance the price could go down

I think the most likely outcome is that the price goes down. But I also think it's possible that the price goes up (decreasing returns to scale) as you try to build more.

> agree that parts other than the battery chemistry do indeed last much longer.

We often depreciate substations at 40 years despite parts inside lasting longer, and we have a whole lot of experience to value that. We don't have a lot of experience with long term lifecycle of batteries. E.g. recycling and decommissioning of batteries at scale is still a big unknown.