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Comment by s1artibartfast | Hacker News Reader

rooftop power is basically the most costly and least efficient mode of generating power. It many places, it easily costs 10x for the same nameplate capacity, and because of suboptimal locations and angles, it only produces a fraction of that nameplate.

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Rooftop power (or other local generation) has a big economic incentive behind it, which is that the energy it generated essentially goes for residential rates as opposed to wholesale rates (which is at least in part actually born out by a reduction in the utilization of the grid). So I expect it to continue to happen, despite it being less efficient in theory than grid-scale. Local battery storage has a similar incentive, but even more accessible (at this point, a home battery system is likely a better house upgrade investment than solar).

Selling rooftop energy for residential rates isn't economically sustainable, and has already been eliminated in California unless you are grandfathered in.

This is because only a small fraction of the residential rates goes to production costs, and the rest go to distribution infrastructure and operations. Distributions and infrastructure costs/ kWh go with more residential production, not down.

Think of it this way. With commercial power you might pay 0.10/kWh production and and 0.30wh distribution. You can make your own rooftop for 0.35/kw, but the grid still costs the same or more, so that gets added to your bill.

Residential rates for rooftop solar only ever made sense as a huge subsidy for early adopters.

I don't mean net metering, I mean if you use 1kWh from your solar panels that's 1kWh you aren't buying from the grid. That's the big advantage which doesn't depend on subsidies.

The key point is that the difference between "wholesale electricity" and "retail electricity" is based on total costs which don't change if you buy 1kWh less from the grid - while it's currently priced "per kWh", it's not really a marginal cost but a fixed one, so people in aggregated would have to pay the same total amount to the grid no matter how much home solar panels are built.

There is a cost advantage currently, but that is a side-effect of how we currently do accounting of grid costs, not reflecting any actual advantage in reducing total costs across the country.

Exactly. Lets say you and your neighbors each pay $100. You put in solar for $90, and save $10. Because most of the power grid costs are fixed, your neighbor is now has to pay $200 to pick up the slack.

This is why California is now considering grid connection taxes, which would charge homeowners for electricity they generate at home.

Consumer rooftop is about the same price range as nuclear.

Commercial rooftop (warehouses, big box stores etc) is a bit cheaper than nuclear, with the most expensive being the same cost as an average nuclear plant, and the low end for new commercial rooftop solar being the same as the running costs of already built nuclear:

https://www.lazard.com/media/2ozoovyg/lazards-lcoeplus-april...

You link is broken, is this the same [1]?.

https://www.lazard.com/media/2ozoovyg/lazards-lcoeplus-april...

It still shows rooftop clearly to clearly have the worst LCOE. I bet the assumptions for Rooftop dont include suboptimal builds, like builds in San Francisco, on a north facing roof, under a tree, with storage.

Rooftop can be good in niches, but it is hardly a panacea.

It's not clearly worst, since it shows that some rooftop solar is cheaper than the cheapest nuclear, there's mostly overlap in prices.

Im not sure why you are looking at the minimum solar costs instead of the average.

We're talking about the UK here.

Ain't no sunshine.

There's enough sunshine to make a difference, despite the clouds and the dark winter.

we went discussing if it can make a difference. spending a billion dollars on hamster wheels for renewable power could make a difference.

The point is that rooftop solar is grossly inefficient and terribly expensive compared to just about anything else someone could do.

Your point is false. Rooftop PV saves (if your roof is suitable) significant amounts on a domestic energy bill even in the UK. I know this from having lived in two houses in the UK that had them, and the calculations that went into deciding to install the first of those, and that panels/inverters etc. have become much cheaper since then. Also, last time I was living in the UK, the grid cost looked like it was billed as a separate line item to the per-unit (kWh) cost, so this really is about the domestic price itself and not just funky billing hiding the cost of the grid like you wrote in another comment: https://news.ycombinator.com/item?id=38158442

The grid scale alternatives — solar farms, wind farms, hydroelectric — can be better or worse in different ways and different times of year, but normal people can't put full size ones on their own property and such wind and hydro scale non-linearly anyway so small ones aren't as cost effective[0].

Furthermore, the reason for the link under which this is being discussed, is that the UK has land area constraints. Suitable areas in the UK for grid scale PV are basically all farms and/or designed National Parks or AONBs and/or designated green belt, and the exceptions (like disused military bases and airfields) have people clamouring over them to build new towns. Sometimes people can get grid scale PV past planning permission, but it's hard work and upsets people with power who want the countryside to look like farmland. Rooftop PV circumvents that.

[0] Except possibly geothermal/ground source heat pump. Those still provide cost effective benefit when you can do them, but the wide price range means I'm not sure which is better.

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