"Try using a higher watt bulb like 24 watts they will stay cooler."
Correct, but I think you mean "volts" not "watts."
In a previous post, I suggested the type 1437, rated at 24 Volts. One of them draws 0.06 amps. Multiply the current draw times the voltage, and you'll get (roughly) the power in Watts. .06 A x 18 V = 1.08 W.