The initial cost of LED's are more expensive than what you would be used to with traditional lighting but the energy saving you can make are huge. By replacing your incandescent lighting with LED lighting you can save up to 90% on your household lighting bills. To get an estimate of how much you could be saving in your home visit
http://www.led-lamps.net.au as they have an Energy Savings Calculator you can use which also calculates the payback period you can expect when you change your lights over to LED's.