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Comment by opo | Hacker News Reader

Generally people who install solar also want to have power at night and when it is cloudy or raining. I think the earlier comment was maybe implying that there would be no grid connection - but that only works if you have enough backup battery to cover all the times the sun isn't shining. Battery costs have not fallen like solar panels have fallen and buying power from the grid would be noticeably cheaper. Even with the subsidies, few people who install solar panels also install enough battery backup that they don't need to use the grid.

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The price of batteries has been falling pretty quickly. They're not quite affordable yet, but I'll eat my hat if they home batteries don't hit affordability in the next 5-10 years.

https://ourworldindata.org/battery-price-decline

That's true but irrelevant to my point.

If rooftop solar costs me $300/MWh, that's a third cheaper than the $450/MWh charged by my local utility provider. So, even without any subsidy or feed-in tariff, it would be rational for me to install solar, use it when available, and fall back to the grid when it's not.

Again, the only point I'm making is that this this statement appears to be true:

  The thing with rooftop/local solar is that it doesn't need to compete with wholesale electricity prices, it only need to compete with retail prices. It's already competitive there [without any need for subsidies]

I'm not arguing for or against subsidies.

>If rooftop solar costs me $300/MWh, that's a third cheaper than the $450/MWh charged by my local utility provider. So, even without any subsidy or feed-in tariff, it would be rational for me to install solar, use it when available, and fall back to the grid when it's not.

If you want the capability of using your own rooftop solar, you need to install a much more costly battery backup system. With a typical solar system, the electrical output is sent to the grid. (So, if there is an outage on the grid, it will also shut down your panels since they don't want you to possibly electrocute the electrical workers.)

https://help.pge.com/s/article/Will-I-still-have-power-durin....

That's true, but again it's irrelevant to my point.

What exactly is the point you are trying to make?

Please see here: https://news.ycombinator.com/item?id=41448190

Yea, it is pretty hard to understand the point you are trying to make and simply repeating yourself doesn't actually help. But to go through in more detail:

>If rooftop solar costs me $300/MWh, that's a third cheaper than the $450/MWh charged by my local utility provider.

The $300 is an estimated LCOE for the intermittent power produce by rooftop solar, not some charge you get in the mail. Utilities can buy or produce that power for much less than that cost.

>So, even without any subsidy or feed-in tariff, it would be rational for me to install solar, use it when available, and fall back to the grid when it's not.

Except as I pointed out, you can't "use it when available" unless you have a battery backup system which the LCOE will be much higher than what you will pay your utility over the life of the system. That might change in the future, but that is the reality today.

>Again, the only point I'm making is that this this statement appears to be true:

>> The thing with rooftop/local solar is that it doesn't need to compete with wholesale electricity prices, it only need to compete with retail prices. It's already competitive there [without any need for subsidies]

I guess you should ask yourself why you think that statement was true? The person who made that comment adjusted their comment to add that actual battery systems weren't competitive at this point:

>>"They're not quite affordable yet, but I'll eat my hat if they home batteries don't hit affordability in the next 5-10 years."

  Except as I pointed out, you can't "use it when available" unless you have a battery backup system

Maybe I've misunderstood, but aren't people already using these systems when available, without battery backups? And just reverting to paying PG&E when the sun isn't out?

ok, I think I misunderstood what you meant. Yes, when the sun is shining and the power grid is alive, you can use your power. People are usually shocked to find that when there is a power outage, they generally can't use their solar panels to have power (unless they have a battery backup system which can isolate them from the grid). But the costs for installing consumer solar are high enough that these systems only had a reasonable payback period when people could sell the power back to the utility at a very high rate. I see that in CA when they finally had to lower that subsidy, demand for consumer solar is estimated to have dropped by 80%:

https://calmatters.org/environment/climate-change/2024/01/ca...

While solar panel costs have dropped very low, the soft costs for installing rooftop solar (labor, permitting, etc.) have only gone up, so one off rooftop solar will always be more expensive than utility solar.

I think you're missing the possibility of:

- Installing rooftop solar

- Retaining the existing grid connection but not connecting the solar to it (or not connecting it in such a way that power is sent back to the grid).

- Running household electrical loads off of the solar when available, falling back to the grid connection when it isn't.

You don't necessarily get full utilisation of the solar energy this way, but you can often still save a whole bunch of money compared to not having the solar. Especially if you are willing/able to load shift energy intensive things like washing/drying to times where the sun is shining.

You can also potentially gain additional savings by having a smallish battery that gains you some additional utilisation without it necessarily having to cover your entire daily usage.

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