But the relevant comparison must now be against the cost of developing solar and sun-related (wind, etc.) energy on the surface of the earth.
(the relevant comparison; must be; against the cost of developing solar and sun-related (wind, etc.) energy on the surface of the earth; T:now)
the relevant comparison
must be
against the cost of developing solar and sun-related (wind, etc.) energy on the surface of the earth T:now