Over the last 3 years, I have extolled the virtues of LED and CFC. LED in particular has 20 times the life of incandescent, uses roughly 1/5 the power and emits zero heat. Over the years, people have said the payback versus cost is not worth the investment. I have showed the 40% drop in my electric bill after converting to LED.
Still it is not enough.
So I spent $5000 converting the showroom to LED (I will seemingly do almost anything to prove a point). We removed 36 50 watt MR16s for 32 9 watt LED. The difference in heat is immediately noticeable.
Before - 1800 Total Watts
After - 288 Total Watts
Only one way to truly be assured of the savings.....We will check the electric bill in one month. You do see a larger savings in a commercial adaptation like Yale. The lights are on much longer, 7 days a week and 52 days a year.
But still you will see significant savings residentially, especially since the low voltage fixture and bulb is pricey itself. This also does not account for savings due to heat reduction.