I like how you are talking about it in $/watt which makes comparison much easier.
The only "honest" numbers you can compare systems with are $/W, pre-incentives. Outside that, there's an awful lot of creativity that can go into making the numbers look better than they really are. See my previous rant about solar salestypes...
And yes with your massively impressive system I am sure it was much easier to get the costs down per watt. I mean if there is a way to do it with it making any economic sense it sure looks like you found it. Lots of space for a huge system, no trees, easy south orientation, sunny location etc.
Indeed, should have gone a bit larger... but this is still overproducing massively. A year in, I'm +6MWh. I draw about 3MWh net from the grid over winter, and I expect our use to be a bit higher the next year with more driving (that's 10-15kWh on days the car moves, and an extra two or so every school day because we're at a really awkward spot where the bus won't stop near us, and there's no safe walking path between our house and the bus stop - at least not for a first grader, it's along a narrow shoulder of a two lane 55mph road where people often do 65+ - and at least the electric isn't cold starting a gas engine for the trips). Though I may trim it down some with a heat pump water heater. I'm also prone to heat on compute in the winter instead of heat pump, especially when it's really cold. Light up some BOINC boxes (it used to be F
@h, but I donated my old office heater to a friend who is doing a bunch of CAD work for 3D printing, which seems a better use of a decent GPU).
In terms of net production, I would be better off with pure south facing panels, but the east-west facing stuff is to capture morning and evening sun, and it works darn well. In the summer, the east/west panels are online a good hour and a half (and hang on that much longer) before the south facing panels come online from anything but diffuse light. They're quite literally backlit in the morning - I probably should have gone with bifacial, but there's enough to shade them from the back that I don't think they'd really produce much.
I've played with the numbers a bit, and the best I can do is about $1.50/W for DIY right now. Interestingly, this is the same for ground mount and roof mount, assuming you're under NEC 2017 and require per-panel shutdown electronics on the roof. My wooden frames are more expensive than a welded pipe frame setup that I'm working on for a friend's setup, and I think future iterations of the concept are going to be 72 cell panels (vs 60 cell). You can go with 10x72 or 12x60 for the exact same thing, but the balance of system costs are a bit lower on 72 cell panels, and it's shorter per "module" (east and west panels, run into a 6kVA inverter). So hopefully next year a few other people locally will put stuff up and we can optimize design on that. I'm happy to help with it, and I'm seeing an awful lot of solar going up in the area. One of these days I should spin up a domain for area solar discussion (of course, with a DIY focus...).
I think a 30 year old solar array is going to be worth nearly nothing.
As used parts, probably, but as a system that still produces energy, it should still be 70-80% of new energy value - probably with a few parts replacements, but it shouldn't be "totally dead" by then, unless nobody has replaced any failed parts. My expectation for my system (I'm ~40, youngest is 3) is that my current system will run with minimum maintenance for another 25 years. If I have to replace a failed panel or two, no big deal, I've got a couple spares, and can also pull spares off my office system (I've got a mini-A over there, with 8 panels I can swap stuff around on if needed). I've got a spare inverter, and they're no big deal to swap. In 25 years, I
hope my kids are out of the house, which should lower energy use (peak draw will probably be in about 10-15 years, with two teenagers in the house, and some more EVs). Depending on how they're producing, I may go through and refresh panels (assuming the power grid hasn't collapsed entirely or something by then, which involves some other changes a lot earlier). At that point... honestly, if I have to worry about them in 30 years after that, I'm crowding 100 and probably won't care. :p
And if the power grid gets erratic, I'm a couple 600V MPPT units away from taking the house off grid. Not as well as I'd like, in terms of battery capacity, but once I get some bigger batteries in the power trailer, I'm a day's rewiring away from being standalone for at least a reasonable selection of loads. I won't be able to run everything all at once, and I'd have to pay close attention to power, and we'd be cold in the winter without a wood stove, but I could do it for a useful amount of power.
It appeals to me to have a level of independence from the grid. I believe there are certain inverters you can buy that give you some power even when the grid is down?
There are a couple tiers of that, the highest end involving a lot of really expensive batteries. Against all odds, Enphase appears to be actually shipping IQ8 inverters, which have some limited capability grid down, and there are the SMA Sunny Boy inverters as well that provide the SPS outlet for up to 2kW of single phase 120V with the grid down. I have those, but as some of my critical loads (well pump, mostly) are 240V, that's of somewhat less use without power conversion equipment. I've got an autotransformer I keep meaning to wire up and play with... but it's honestly pretty annoying to drop grid power to the house, so I haven't been experimenting on the house much. I really need to run a new outlet box as well for some higher loads, and I'll do that when I run an additional run for a hot tub (if I use it or not, it involves a subpanel that makes my life a
lot easier, or I might be able to squeeze a few more breakers together with the quads mini clusters..).
Just be aware that going this route is quite expensive.
An Automatic Transfer Switch (ATS), acting like a reverse computer UPS, defaults to solar power and switches over to grid power when needed. Because the panels aren't grid-tied, there's no need for an electrical permit, at least where I live. The downside is that there's also no net metering.
There are a couple ways things can be wired, and in the US, most references to an ATS are a device that drops the whole house from the grid, allowing you to island and run the house when the grid is down, if you have batteries. You can also get standalone inverters like my office has that allow people to do what you're talking about, running off solar and battery unless they're low, but... "no permit required" is really going to depend on the area. Talk to your local electrical AHJ, because that's not generally true.
Some time ago SMA made an inverter that would feed one circuit from your panels, even if the grid was down, but I can't find it now. It's probably no longer available as it wasn't terribly useful and battery backup systems of various types are only slightly unaffordable rather than eye-wateringly unaffordable.
All the Sunny Boys have the 2000W SPS outlet. I've 20A/120V outlets wired to all three of my inverters with the proper switch to enable them. There's some complexity if you have rapid shutdown devices on the panels, but there's a way around it that involves putting 18V on the secure power supply pins, which lets the controller tell the panel devices that they can open up and provide power.
