[NullPrefix]

60 Watt incandescent can be replaced by under 10 Watt LED. Assuming 50 Watt savings.

Assuming $0.10 kW/h (California is $0.16 ??). 1 hour of LED burn time saves 50W / 1000 * 0.10 kW/h = $0.005

Assuming LED bulb costs $2, assuming incandescent bulb is free. $2 / $0.005 = 400 hours until break even.

[jwilk]

You got the units wrong, but the end result is correct:

50W × $0.10/kWh = $0.005/h

$2 / ($0.005/h) = 400h