With the new economic LEDs that can be retrofitted to any existing lighitng eveybody can savup to 90% in the electricity bills.
LEDs present many advantages over incandescent light sources including lower energy consuption, longer lifetime, improved robustness, smaller size, and faster switching. LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluoroscent lamp sources of comparable output.
But if are used for more than 4 hours pre day in few years time they earn their original expentiture.