[ClumsyPilot]

"You essentially have a "break even" point 20 years in the future, from there onwards you start saving money."

That's exactly how a 5% roi investment works. There is nothing unusual here.

"in less than 20 years time it is possible that someone comes out with a mega-para-hyper-ultra climatization device that makes yearly energy costs go down by (say) 90%"

And it's possible second coming of Christ will happen, or an asteroid will fall, and you'd be better off soending money on hookers and cocaine.

A plan that relies on some unrelated events to solve your problems is not a plan. Why bother planning at all then?

[jaclaz]

>That's exactly how a 5% roi investment works.

Not exactly, in a 20 years 5% roi investment you normally get your invested capital (admittedly reduced in real terms by inflation) back.

In this case a the end of the 20 years you have something that has degraded and that probably needs replacing (talking of ventilation systems or solar panels) and/or needs repairs.

I find it more like a 5 year lease for a car vs buying it cash.

[renewiltord]

This was a problem that hit the first solar adopters. Their break-even was so far in the future because the technology really ramped up later. Of course, one could argue perhaps that wouldn't have happened without the adoption. And perhaps argue against that again that it was gov subsidies that really pushed solar to primetime.