We should teach energy efficiency in the primary schools. If it were feasible I would have energy efficiency taught in the crib, or alongside potty training. Energy efficiency and climate change are issues that will affect absolutely everyone, the very young, the very old and everyone in between. No time is too early.
Yes, energy efficiency should be taught in primary schools, because it is important to learn good habits when children are young. Also, children can go home and teach the good habits to their parents. Children should learn to have respect for the earth, because it will come naturally when they are adults.
I think energy efficiency should be taught in primary schools. It's a good thing for students to learn about energy conservation, and different types of energy. They should at least hear about the basics of energy efficiency. Ultimately, they will inherit the planet along with any and all of its energy problems, so it makes sense for them to learn about energy efficiency.
Teaching children to be responsible in many other ways begins at this age, so why not teach social responsibility regarding energy and other environmental issues in primary schools, too? I grew up in the 1980s, and even I remember being taught basic, simple efficiency tasks then such as turning the lights off when leaving a room.