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Comment by balderdash | Hacker News Reader

11-13yr payback on something that is going to degrade ~3-4%/yr for 10 years (and limited terminal value) doesn't seem like the greatest investment unless you think the arb is going to widen a ton.

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Alternative systems are closer to 5 years payback if you have access to off peak energy. 3-4%/year degradation is very high, battery packs available in the UK from Fogstar are rated at 8,000 cycles with a 95% depth of discharge.

FWIW my high voltage battery pack has almost 365 cycles and is still at 100% state of health.

FWIW i was just going off that fact that the warranty on the battery mentioned in the article only guaranteed >=60% after 10 years...

And any arbitrage is also trivially exploited by the electricity company, who has a much greater financial incentive and scale, so there's really no reason to think that it's going to widen in the future either.

You could exploit it yourself, but only if you have several million to invest, less than that and it isn't worth the bother for the electric company to talk to you. Even at ten million invested you really need to have this is round one in your proposal with the understanding you intend to invest a lot more when it proves in the real world to work like you expect.

Until grid-scale batteries are more established, you're helping the electric company, and that's why they're exposing the arbitrage. They're providing the incentives to nudge demand, so a home battery is doing exactly what they want (use more at time X, use less at time Y). Otherwise they'd just have the 24/7 price be whatever it currently costs when the supply and demand curves are tightest for them (when demand is highest and/or supply is lowest).

Add in that my freezer probably contains over $500 of food (and the fridge has less, but not none.)

Usually you can buy ice, but when I had a ~36 hour outage a couple years ago, I couldn't. Most stuff was fine for that long, but 2-3 days would've meant tossing pretty much the entire contents.

(Plus, I don't have cell service where I live, so being able to power my router is pretty useful.)

This is probably a bad move if you live in a city. It makes more sense in rural areas.

Let's assume the calculation is correct and you actually earn back in 11-13 years. You are better off investing the money in something like the S&P 500 where you'd double your investment in about a decade without the hassle.

Things will start to get interesting where €1600 don't buy you 5kWh but double or triple the amount.

I can imagine most people are better off either investing like I said or in insulation.

But that makes you more dependent on externalities, a battery makes you more independent instead.

Having just a battery still makes you dependent on externalities, just offset by a few hours.

€1500 can already get you 16.1kWh.

The investment point still stands, though you could argue both come with risk/reward, energy prices aren't guaranteed to be stable.

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