The idea that solar technology/pricing wouldn't improve markedly during the twenty years of phases 2 and 3 to the extent most property owners, rather than renewing for an additional ten years, would tell SCTY (now Tesla) to "get that antiquated mess off my roof" always seemed like an inevitable outcome --yet lease/PPA extensions between years 20 an 30 were a major component of the financial "no brainer" justification for buying out SCTY. If removals rather than renewals ensue, phase 4 will not be monthly cash flow receipts but a profit/cash drain.
As a vague/rough, fractal data point of >1 and <2, with a
20 year interval
I have 2 PV systems on 2 roofs, both face due south (well appx 185 - 190 degrees)
First system has 32 BP MSX-43's (43watt, now maybe 35 watt output after 20 yrs Amorphous Silicon tech) technology appx 1996-97 that cover
26sq meters for a whopping ~1.376kw (now 1.1 kW) array installed spring 1999
Second system has 37 Hanwha Q Cells Q.Peak Duo BLK-G5 315 watt panels covering
59.9sq meters for 11.655kW array installed Dec 2019
So appx 20 years later, covering ~twice the area, I get ~11x (eleven times) the power. the technology is getting better
(11.655 / 1.1 = ~10.5)
However, after 20 years, the _technology_ still produces power from sunlight
(as an aside, the low power array is being removed so the house can be re-roofed and then newer technology will be installed, the old PV recycled somehow and another "monster 150-200%" array (non shaded) (its illuminating how tall trees can grow in 20 years, plan ahead)
i think its complex. To me, it seemed SCTY designed to get a large number of houses, fast, w/Solar PV and get folks into the system, after all, PV in 20 years
1997 Megawatts installed on the _planet_
235 megawatts consumed around 0.7 terawatt hours
2016 Megawatts installed on the _planet_
301 GIGAwatts consumed around 333 terawatt hours
(Sources: IEA Photovoltaic Power Systems Programme, IRENA, Solar Power Europe, EurObserver, and national sources.)
and (BP statistical review of world energy 2017)(2018 comes out around June)
(as an aside, folks might be interested at how the marine folks are using electricity)
April 2019 Electric & Hybrid Marine Technology International - UKi Publication Viewer
(april 2019 hybrid electric and hybrid marine publication)
preaching to tha choir, eh