Replace all standard light fitting to compact fluorescent lights. They consume about 70% less electricity. Although these lights are a bit costlier, you will get its benefit in the long run. The money you save from electricity bill will surpass the cost difference within couple of months.
If you are considering replacement of roofs, change to glazed tiles. It will deflect the sunrays and keep your room cooler. Use light colored roof tiles.

Install motion detector light sensors in the rooms. It will light only when there is motion and you are safe from unnecessary electricity bills.

Try to minimize water wastage. Seal the leaks from all the pipelines. Use cold water while laundering as much as possible. Make water saving a family affair.These are the basic eco friendly home improvements.