I am curious, not trying to bust your chops or anything but how can you justify the cost on something that will never pay a return? I cannot see it ever being a good investment at todays prices at least.
p>The downside to this approach is that in a few years, solar panels will be even cheaper and more efficient and the resulting loan payment will be even less and you'll be stuck saving less than you could have saved had you waited. In other words, do you want a net savings of $30/month starting today for 20 years, or wait 3 years and have a net savings of $50/month for 20 years?
The problem with this kind of statement is that it is an overall generalisation that can be applied to ANY industry, and will never have a set definite cutoff date. You can say the same thing about buying a computer... why buy now when you could buy a cheaper more efficient one in 3 years... and that statement holds just as true in 1995, 2000, 2005, 2010.
In 1995, you may as well just live without a 486 or Pentium computer until the more efficient Pentium II comes along in 1997, but wait, there's a more efficient Pentium III, but wait, more efficient Pentium IV, but wait, Core, but wait, Core II Duo, but wait, Core i3, i5, i7, but wait, next step in development... if you kept putting off a purchase like that, you'd never get the item.
The same goes with solar panels. Is it a huge leap in logic to consider that the panels of today are cheaper and more efficient than those of 5 years ago, or those of 5 years before that? I could probably guarantee that whatever units are available during today's administration are cheaper and more efficient than those installed during the Carter administration, and the ones in 2015 will be better still, and in 2020, even better still.
At some point, the balance of efficiency gains versus cost saving versus life of the item has to be weighed.
Another possible way is to find some way to spread your purchases over time while still staying compatible through the whole system. Say you need 10 panels to power your house completely over 20 years lifetime per panel, plus backend equipment with 20 year lifetime. Purchase one panel every 2 years, and at year 20, replace the first panel and the backend as its lifetime is up and efficiency is waning, and continuously upgrade every 2 years ad infinitum as your equipment dies. True, you will not get the full benefit of power savings immediately, but you WILL reap the benefit of having a system that is utilizing the newest and more efficient tech over the years as opposed to a static system that is altogether 20 years outdated. The efficiency will average out, assuming all items are swappable and compatible with one another... true, it will probably be about as efficient as a complete system slightly older than the average age, but at the 20 year mark, an 11 or 12 year old averaged system is probably more efficient than a 20 year old complete system, and is cheaper to upgrade a single panel to keep that average than flat out replacing the 20 year old system.