This is something known as Jevon’s Paradox. If we advance technology so that we have to use less of a resource to do something, great, we might do so. But we might have made it so much cheaper that we actually end up using more of it. Which way it goes isn’t really known until we see what actually happens. Historically, light has been a “normal good.” Whatever the price of it, the technology used to create it, whatever our own incomes, we seem to spend about the same portion of our income on it. This has been tracked through candles, gas lighting, electric, incandescents and so on. Whether it’s going to hold true for LEDs we just don’t know.