Total cost of bulbs and energy: $56.90 minus $13.96= a $42.94 payback
on $1.7 invested!

The difference in the cost between the two bulbs is $1.70. If you invest that now, it will put $4.23 back in your pocket every year, for a total of $42.94 during the 9.1 year life of your investment.

That is equal to earning a 277% annual return on your $1.70 investment!