Well, it depends on what you mean by efficiency. I would say that if I say "I have these solar cells that take sunlight and create electricity with 12% efficien

Well, it depends on what you mean by efficiency. I would say that if I say "I have these solar cells that take sunlight and create electricity with 12% efficiency", I would expect that I get 12% of the total insolation in electricity. If I instead say "these solar cells take infrared sunlight and create electricity with 12% efficiency", then I expect it to be 12% of the infrared sunlight, not 12% of the total sunlight. It depends on what the hypothetical "fully efficient" case is.