PT 65 S1 Q3

Millions of homes are now using low-energy lighting,but millions more have ... ...

Information about which one of the following would be LEAST useful in evaluating the argument?
(A) the actual cost of burning low-wattage bulbs compared to that of burning normal bulbs
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Dec 2011 LSAT (PT 65): Logical Reasoning A