Thanks - I didn't know about Inspire Index, I'll check it out. I tend to agree about false precision. My first instinct was to use the synthetic horizon for addresses in that group, but I think that's over positive. A range might be better (if a bit more complex)?

These calculations often fail to account for present vs future value of money.

If you’re financing the system you have no big cash outlay, but returns are further out, possibly never when accounting for the useful like of the system.

With cash up front all the returns are yours, but they are much lower than what that cash would net you in an average investment.

The financial math on small solar systems can be complex. If the system is sufficient to provide power to major appliances in a power outage (assuming you have a power outage risk in your area), it can make more sense to tie money up in these systems.

Why would you replace it if doing so is uneconomic?

Panel lifetime is very high. The scope for efficiency improvement is not huge (unless there is a cost breakthrough in multi band photon capture). It's not a car, phone, or computer. It's more like the rest of the house electric infrastructure.

I had my rooftop solar over 10 years ago and basically intend to leave it until some maintenance issue forces action.

(Also, the kit secondhand value is hard to determine but far from zero; 30-50% maybe?)

The technology is unlikely to improve meaningfully in 7 years. And you'd only upgrade if it was a financial improvement so it makes complete sense to give an estimate based on keeping it for 20 years.

I don't see what your issue is.

Depends on your energy requirements and future technology and energy costs. At the moment, one should value this outlay as a fixed income equivalent investment [1].

The panels have a ~25 year warranty though [2] (at which point, they should still produce ~80% of rated output), so it’s entirely possible to just leave them in place. At a certain age (~55-60), these are the last PV panels you’ll need to buy, as they’ll potentially outlive you (assuming developed country life expectancy).

[1] https://magnifina.com/articles/rooftop-solar-yield/

[2] https://www.energysage.com/solar/solar-panel-warranties/

I noticed this as well! Very interesting.

Thanks! Should be doable, I just got excited by the new shiny thing first.

Absolutely! I have some other datasets that might be useful too (e.g. air quality). Drop me a line: ruaraidh[at]southlondonscientific.com :)

Let me know if you’d like access to alt net availability data

Good idea. I want to add specific options for different mounting locations (sheds etc) as well.

You can put it on the ground if you like

Oh, that's such a good idea! I suppose the challenge is knowing where there are installable surfaces are (or at least making defensible guesses). I'm going to have a go at this...