My system payback was actually a lot faster than the original planning document outlined. Payback was in 4 years and 9 months. Paid off in August of 2018. The solar generation credit of 30% of the system value was deducted from my first two years tax bills. Plus I pay a lot more for power than you I suspect. My power tariff has ranged from $0.13 - $0.52 kWh depending on the season since I put the system in.
Generally I knocked about $175 off each month's power bill since installation. My annualized ROI was around 22%.

Wow, an American paying more than a Brit!? I thought power was cheap everywhere over there. I've also never seen a variable power bill - you pay differently per season? Mine is fixed at about 21 US cents per kWh. Your 13 cents is what I usually hear Americans quoting for all year round.

Is it California I saw in the news getting rolling blackouts during the heatwave? They charge you that much and they still can't invest in enough power stations. Maybe it's all the treehuggingness in that state! California is the one with severe restrictions on car engines? Probably only use green power generation too, which we all know costs a fortune. The UK government throws money at wind farms.

By the way, all my engines are switched into Milkyway gear, and I believe I'm only a few places ahead of you.... yip, 357 to 362. [Beckons cheekily over my shoulder]

Well, the $0.13 was the lowest I ever paid when I was on an EV rate that the utility cancelled this year. I got that rate from 11PM till 7AM to charge the car. Now I am on a two tier daily rate. Off-peak at $0.24 from 9PM till 4PM. Then peak from 4PM till 9PM at $0.40. That is for Monday-Friday. Weekends and holiday are all off-peak hours. Summer season is from June 1 thru September 30. Winter season is from October 1 thru May 31. Winter power rates are about 5 cents cheaper for the same time periods.

And you are absolutely correct in that all our "tree-hugginess" is what got us in trouble. No gas power peaking plants can be brought online fast enough for peak demand. Peak demand is when the sun goes down and all our solar generation and "green energy" goes away. Only one operational nuclear plant left running and that one soon in decommission. One of the peaker plants was out of commission this past week. So threat of rolling blackouts. We are also subject to safety blackouts when it is "red flag" conditions which are when it is hot and windy and low humidity. Which is every late summer, early fall actually.

And the entire West Coast and SouthWest was under extreme heat for the past week so everybody was using all the power they locally generated, so none to purchase from any excess generation from other states. We are suffering from the "duck curve" in generation and consumption. Google the term to understand it. Poor planning coupled with the socially green mantra is the problem.

What are these safety blackouts? How can generating power cause fire?

These go back a few years.
There were a number of very serious, fatal, forest fires that were attributed to powerlines failing setting fire to the forests they ran though. These fires were associated with extreme wind events which either caused the lines to break (probably at poles?) or the cables hitting trees (or arcing to trees). To save money, face, whatever, the power companies shut off power in vulnerable areas, so the lines are dead in the event of wind damage. At least one power company has been forced to near bankcrupcy as a result of these fires and the damages they've had to pay.

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Sometime located elsewhere in the (un)known Universe
But most often found somewhere near the middle of the UK

In a eutopian landscape one would - but large tracts of California are heavily forested and massively crinkly. Many of the rivers have fairly small hydro-electric power plants in the bottom of the valley, but the towns are some distance away further up the hills (and have grown into the forests) Thus the only way to get the power to the town is through the forests.

In California the distribution lines are (by our standards) quite low voltage, and so can be nearer the ground, and, let's be generous to the fine citizens of the USA, some of the line tracks and pole lines are not maintained to the best possible standards. Actually, here in the UK there are quite a number of places where "low" tension distribution lines run through trees, and they do cause problems - my brother lost half a barn thanks to a tree being set on fire by an errant cable....

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Sometime located elsewhere in the (un)known Universe
But most often found somewhere near the middle of the UK

Setting them on fire? How does electricity consumption cause that? Isn't that by thunderstorms?

I have AC in my home, but that's because I hate the heat (over 25C indoors is not acceptable) and just built a conservatory which has huge solar gain. I might save a fortune in winter on heating, but it's costing me AC money in summer! And no I can't open the windows, I have 12 parrots flying about.

So you use almost as much power with about half the population. So more, but not astronomically more. You'd think the richest country in the world could provide better power....

Utilities cause fires by not maintaining their distribution lines and equipment to protect their shareholders income. And letting unmanaged undergrowth provide tinder to start destructive fires when their equipment fails. So you have utilities completely destroy cities of 90,000 populations and kill 300 people.

Wow, so expensive, ever considered moving to another more sensible state?

I would have thought in a country as big as the USA that states could just share power. Do you actually have power plants that belong to a certain state? In the UK, we don't have a Scottish power station and an English one. The national grid connects anything to anything, with links to France, Netherlands etc when necessary.

This seems to suggest your solar is only a small proportion of generation:
https://en.wikipedia.org/wiki/Duck_curve#/media/File:Duck_Curve_CA-ISO_2016-10-22.agr.png

What are these safety blackouts? How can generating power cause fire?

You need to go for things other than solar, offshore wind or something.
Or.... this looks interesting:
https://en.wikipedia.org/wiki/Vehicle-to-grid
Once everyone is on electric vehicles, you'd have a massive battery bank to shunt power in and out of. Once solid state batteries are in use, things will get a lot better.

Are you accepting my Milkyway challenge?

No, no state owns any generation. The power companies own generation. And that duck curve graph is from 2016 and before the incentives for building solar were started. Massive solar production was installed after that. Today solar generation is 3X the value in that old 2016 graph.

We do have lots of wind generation in California too, but nothing built recently because of "not in my backyard" local restrictions and opposition. No offshore wind generation on the West Coast but there are planned large offshore wind projects planned for the East Coast. Biggest wind installations in the past few years have been in the Mid-West and Plains states.

The safety blackouts are the utilities covering their asses when the wind blows and the possibility of a fallen tree starting another fire, they eliminate the risk by shutting off power for the area until the wind dies down. If they had trimmed the trees near the equipment on a regular schedule they would not have any risk of a fire starting because no tree would fall near their equipment.

And the utilities are starting to experiment with large scale battery storage to charge up banks of batteries when the excess solar generation can't be used. Then the battery banks can be used to maintain the grid during high power consumption periods or when conventional generation is offline for maintenance or failures. But they need about 100X more battery storage than what they have currently.

Setting them on fire? How does electricity consumption cause that? Isn't that by thunderstorms?

I have AC in my home, but that's because I hate the heat (over 25C indoors is not acceptable) and just built a conservatory which has huge solar gain. I might save a fortune in winter on heating, but it's costing me AC money in summer! And no I can't open the windows, I have 12 parrots flying about.

So you use almost as much power with about half the population. So more, but not astronomically more. You'd think the richest country in the world could provide better power....

Utilities cause fires by not maintaining their distribution lines and equipment to protect their shareholders income. And letting unmanaged undergrowth provide tinder to start destructive fires when their equipment fails. So you have utilities completely destroy cities of 90,000 populations and kill 300 people.

Wow, I thought with the American suing culture, they'd be very wary of anything going wrong.

Not for utilities which have certain legal protections. But my local utility, the one that destroyed the city of Paradise and killed 100 people IS in bankruptcy. Massive fines and lawsuits are currently in process. But all they care about is protecting their shareholders. And keep raising my power rates to pay for the lawsuits and fines caused by their negligence.

And the utilities are starting to experiment with large scale battery storage to charge up banks of batteries when the excess solar generation can't be used. Then the battery banks can be used to maintain the grid during high power consumption periods or when conventional generation is offline for maintenance or failures. But they need about 100X more battery storage than what they have currently.

I didn't think current battery tech was good enough for that , way too expensive. The new solid state ones should be better though. I read 5 times cheaper, 5 times the life, 5 times the capacity, and 5 times the charging rate.

There are lots of ways to store energy, the oldest is pumped hydro. You let water out of a dam during the day and charge the going rates for the power. The water flows into an afterbay or reservoir below the dam for holding. Then at night when the power rates are cheapest, you run the turbines backwards and pump the water back up into the dam for another day of generation.

You also have kinetic energy systems and compressed air systems for storage. Currently, California has about 100MW of grid-scale battery storage online holding about 325MWh of energy. In process is around another 60MW of battery storage almost ready to come online in 2020.

There are four regional power interconnection grids in the U.S. Western, Eastern, Texas and Quebec. There are 3,300 power companies in the U.S. There are three major Investor Owned Utilities that provide the majority of power to most Californians with 3 other much smaller regional utility that serve remote communities.

Sorry, but the Scotts didn't invent pumped hydro-electric. That honour goes to the Swiss in about 1905-1910. Their initial schemes used separate pumps and generators. If I recall it wasn't until about 1930 that the reversible combined pump-generators came along - that may have been in the USA as, again from memory their first scheme round about the same date.

It is quite spectacular to be near the Ben Cruachan station's outfall when it does a full rate run-up from zero to full power in a couple of minutes, and if you are in the wrong place, and the wind is blowing hard, one gets very wet very quickly. The incredible thing is once running at full power (>400MW) there is far less spray than during a full rate run-up!

Less to do with hugging trees, more to do with not setting them on fire.

Setting them on fire? How does electricity consumption cause that? Isn't that by thunderstorms?

Above ground power distribution, winds, humidity in the single digits.

https://www.nytimes.com/2020/06/16/business/energy-environment/pge-camp-fire-california-wildfires.html

One of those "batteries" https://en.wikipedia.org/wiki/San_Luis_Reservoir

Do you get to pick your power company? Or do you have to use the local one, then that company buys and sells power to the neighbouring one as required?

The Scots invented that - the Cruachan dam built in 1959, which stores 7100MWh, more than all the batteries in California. We have a lot of water. :-)
https://en.wikipedia.org/wiki/Cruachan_Power_Station

No, we get no choice of power companies. Each company has a service area that nobody else can poach from.

I used to live next to Castaic Lake in SoCal. Castaic Power plant (1247MW) is the pumped hydro plant. Castaic Lake is the holding reservoir for the water coming from Pyramid Lake forebay above it. It has a 7.2 mile, 1060 foot drop from Pyramid Lake through 30 foot diameter penstocks down to Castaic Lake. Pretty significant use of kinetic energy.
https://en.wikipedia.org/wiki/Castaic_Power_Plant