stp53, if you look closely at the aerial image to this video...

stp53, if you look closely at the aerial image to this video file before you hit play, it provides a clue as to why Musk's latest "insight" has a few problems.

The shot clearly shows a number of roof planes on the houses shown in sun, and many in shade. (Doesn't matter IMO what time of day the shot was taken to illustrate my point)

To build (or replace) an entire roof with PV tiles means only about half would ever be solar energy generating. For those in America directly south-facing roof planes, and those to the south-west. Directly east (morning) is no good, producing little return.

In Oz, replace "south" with north obviously - but essentially the same problem - current PV panels have to be orientated to the solar path where you live. If they are fixed in place, even more inflexible.

Given the limits on efficiency (and good luck to Dyesol to strive higher), solar PV is spreading quickly around the world as the pre-eminent renewable power source due to low costs. Hopefully the reduction in feed in tariffs wont stifle the industry greatly and it can adjust.

So to spend $ 20 k on a new roof, of which half at best generate power is a big price to pay for aesthetics - which Musk really seems to be appealing to here - the comfortable middle-class of America and beyond. A utopian vision with his cars, his batteries and his roofs throughout the world.

There is another one called tractile which combines water heating as well, which I prefer, however both systems must accept the limitations imposed by the sun's movement, and then if they can compete in terms of LCOE with conventional PV, then they might have something.

Cheers BC