[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.