They vary too much to have such confidence, and the technology changes so it would invalidate any real world tests with a previous technology.
That 1% finger in the air estimate is what installers or sales people tend to use to give people a vague idea what to expect. Your panels will not make as much power in 25 years as they do today. But because weather happens the hypothetical input power - sunlight falling on the panels, can vary maybe 5% from one year to the next, larger than the degradation in any single year no question. So it's very possible a solar PV roof has its "best" year in year two or three even though that's not intuitive.
alt Hacker News
They vary too much to have such confidence, and the technology changes so it would invalidate any real world tests with a previous technology.
That 1% finger in the air estimate is what installers or sales people tend to use to give people a vague idea what to expect. Your panels will not make as much power in 25 years as they do today. But because weather happens the hypothetical input power - sunlight falling on the panels, can vary maybe 5% from one year to the next, larger than the degradation in any single year no question. So it's very possible a solar PV roof has its "best" year in year two or three even though that's not intuitive.