Lighting doesn't consume much energy. Most if it goes to transportation, industry, and home water heating and air conditioning. In all those areas, we've taken our first baby steps towards conservation - there's tremendous room for improvement in without much real impact on our lifestyle.
One example: about 45% of industrial energy use goes towards producing steam. Steam systems are typically a hodge podge and pretty inefficient, but they're relatively easy to make far more efficient with some simple, inexpensive changes that typically pay for themselves well within a year by increasing energy efficiency by up to 25%. Almost no steam plants have done this yet, but nearly all of them a looking for ways to improve efficiency.
One thing our species is really, really good at is adaptation.