And, of course, if you have a 24-volt alternator, charging a 12-volt house system from the main engine will cost a bundle.All of this far outstrips the extra cost of 24-volt bulbs (the fixtures are the same -- no such thing as a 12-volt incandescent fixture vs. a 24-volt one) and even the cost of a 30-amp equalizer.Lastly, I will point out that 120-volt items are almost universally less expensiv