[SauronOfMordor]

40% is very high

Once you have achieved 40%, the game then becomes how cheaply can you make them and still maintain the efficiency.

The Total Cost of Ownership for solar power has as main components

1. Capital cost of the solar cells
2. Cost of the real estate they occupy
3. Depreciation (how long do they last before they need to be replaced)
4. Operation (Washing the dirt and bird droppings off them so the sunlight can get thru)

[Covenantor]

ummmm ....you forgot the real biggie. Energy storage, that means batteries. And that to the real estate as well as control circuitry. Last time I looked that doubled the installation cost. Imagine the user disposal fees(taxes) that will be imposed once the storage batteries come to the end of ttheir life span