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Comment by AndrewGaspar | Hacker News Reader

Can somebody explain where the return on investment comes from in residential solar? It just strikes me that if there was easy money to be had on solar installations, we'd just get tons of utility scale solar installs (which would likely by more capital efficient) and my utility bill would over time converge on the expected total utility bill for a home with residential solar. Is it just because we're in that transitional period where utility scale solar _is_ being installed, but in the mean time residential solar install internalizes the savings to your own residence? Or is it because most of the testimonials are hiding the ball a bit (only net savings reported due to buyer's remorse, etc.)? Or is it because government subsidies for residential solar are distorting the true capital cost, and thus profitability, of solar at scale?

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To be fair, there is a lot of grid scale solar (and wind) being built, largely because they are the cheapest way to add generation capacity right now. But they are not a simple pluggable replacement for gas, coal, or nuclear, because they deliver power to the utility grid when the weather dictates power is available, not when the utilities demand dictates they need it. Utilities struggle once the fraction of their power supplied by these "interruptible sources" gets over 1/4 or so of their total generation base. As far as I know, the only regional-scale grids that have gone completely to renewables are Tasmania and Iceland. South Australia is not far behind, and Scotland not far behind them. But each has special circumstances that make it an easier lift. Tasmania and Iceland have abundant hydro and geothermal, which are ideal complements to interruptible renewables, because they can be quickly throttled up and down as required, as the interruptibles wax and wane. South Australia has highly reliable sunshine and wind, and so have been able to bridge the stochasticity of these with relatively manageable sized batteries (and a couple of flywheel installations to provide very short term momentum based frequency control). Scotland has highly reliable wind, and is headed in the same direction as South Australia.

> we'd just get tons of utility scale solar installs

This is happening, in a big way: https://emp.lbl.gov/utility-scale-solar/

The main limitation AIUI is grid interconnections, i.e. there are a lot of projects in the backlog that can't be built until the utility approves and prepares for it.

https://emp.lbl.gov/queues

> The lists of projects in this process are known as “interconnection queues”. The amount of new electric capacity in these queues is growing dramatically, with over 1,400 gigawatts (GW) of total generation and storage capacity now seeking connection to the grid (over 90% of which is for zero-carbon resources like solar, wind, and battery storage).

Residential solar reduces retail power costs @ $0.30/kWh, whereas grid-scale solar supplies wholesale power @ $0.02/kWh. (Representative figures from California.) NEM (net energy metering) amplifies this effect.

If you look at a system-cost ROI analysis, the difference between residential and grid-scale is that the latter requires more transmission lines and provides fewer jobs (which is a key part of the political economics), but residential solar comes out looking very bad.

Explicit subsidies -- which pay a part of residential solar capital costs -- are a much smaller force.

We are getting tons of utility scale solar:

> Utility-scale solar power generation in the U.S. is surging. This year, almost half the 46.1 gigawatts (GW) of generating capacity added to the grid will be solar, according to the U.S. Energy Information Administration, and solar has contributed more than 30% of all new capacity in five of the last six years.

https://news.sap.com/2022/11/the-take-utility-scale-solar-su...

Residential solar has no complexity for siting, transmission infrastructure, takes different skills to install, and let's relatively wealthy people move fast.

Because with net metering you can generally sell at a much higher price than the wholesale rate. It was a loophole that is now going away.

Utility-scale solar is far more efficient than rooftop solar. With rooftop, the panels face whatever direction the roof does. But utility solar fields have panels that rotate to face the sun.

Considering that power generation depends on the cosine of the angle between the sun and the panel - angle matters a LOT. Efficiency falls off fast if your angle is bad.

This should be at least somewhat offset by the fact that you generate power approximately where it is consumed, so the grid doesn’t have to grow as much. Turns out it isn’t so simple due to peak demand vs peak production etc but still. I wouldn’t have a problem with plastering PV on half of Nevada.

Most solar panels are angled to the South to capture the most sun. I read somewhere that fixed installations are better because:

1) The money spent on panel rotators can be invested into having more solar panels.

2) Affixed solar panels are significantly more storm and hurricane proof. If there’s one bad storm with rotating panels, your investment principal is gone.

3) Maintenance costs increase when these moving parts eventually break. Fixed panels have no moving parts.

> Can somebody explain where the return on investment comes from in residential solar?

During the run-up on housing prices over the last couple of years, there was a belief that an owned solar system would raise your house's sale price in much the same way that a kitchen or bathroom renovation would.

Couple that with the supply and labor constraints, which made it hard to get the panels, battery, and installers you wanted in a timely basis - that raised the perceived home value yet again, because if you wanted to add your own solar later, it wasn't seen as easily doable.

I don't know that the ROI was ever great, but with both of those factors gone today, it's worse than it ever was. (Source: shopped for homes in 2020-2021, bought in 2022, tried to get solar installed, ROI made no sense.)

I would say most people can't afford 25k$ investment cost for something relying on governmental decision that can change on a whim

In California, there's no choice for new housing, where new single/multi family houses must have panels that cover 100% of energy usage for the year (or as much as the roof surface area allows).

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