And what you need to know before embarking on an endeavor which may or may not be worth the effort in the first place. Keith, in the second post in that thread, put it very succinctly.
I suspect we are paying a great deal more for electricity out here, than you are in New Hampshire. I have to run chillers not heaters, a typical system could easily have 400watts of heater or more, before a heater is even purchased.
Another energy saving move is to drop your aquarium water temp to the high 70s: 77 - 78°F, rather than up at the high end in the 80s. (82 - 84.) The other bonus is more oxygen available in the water. Also, as pointed out in that thread, many people set up their systems to be very efficient water chillers, which increases their energy consumption even more.
To answer your question directly, anything in contact with the water has to be titanium or better (graphite, gold, and platinum come to mind.) There are some exotic stainless alloys, that could be used, but they can be expensive, and some other metals on the Noble or Cathodic end of the galvanic chart, but hard to find.