On a sunny day (Fri, 16 Apr 2004 06:40:16 GMT) it happened
wrote in :

ou also have to take into account
the degradation of the system capacity over time.
That would be 80% of capacity I think.
And yes, you could take the kWh price of 25 years ago,
that of today, and draw a line, it will point up,
extrapolate to + 25 years from now ,and you have a value.
The other thing that will help is the inflation, you
can roughly say that money halves in value every 10 years.
This has 2 effects, now, if you did have a loan for the solar
cells, and you pay 2% of your income, in 10 years this will be
only .5 % and in 25 years the amount you have to pay will look
ridiculously low.
From this we can see that borrowing is not a bad idea perhaps.
Also that still leaves you with all the cash you can spend on
other things now.
JP