harry landis wrote:
Sunpower sells 19.7% efficient modules using 22% efficient cells: http://investors.sunpowercorp.com/releasedetail.cfm?ReleaseID=238439The world record for a single cell is about 42%. But the most important number is watts/$, not watts/area. First solar claims a manufacturing cost of $1.40/watt for their thin film CdTe panels.
Mmmm. Sort of. Keep in mind that lower efficiency panels are heavier, require more install materials and most importantly take up more *space* per watt. All of that limits how much you can put on a roof.
Also power output depends on how much light the panels get. For example my polycrystaline panels put out about the same amount of power as the single-crystal panels in full sun. However when there is a cloud or on a hazy day the single crystal panels drop power a bit. The polycrystal panels drop power like a rock.
Thin film is worse.So like everything else, it depends. I personally believe that single crystal panels are worth the extra price per watt: If you're going through all the trouble to put the things up there you might as well put the best you can and as much as you can.
Chris