Look for LED (light emitting diode) lights.
They will last 10 times as long as standard lights and will use 90% less
energy. In addition they do not get as hot as standard bulbs.
They are also much more durable and will not break as often.
300 lights, 5 hours a day for 45 days:
A standard C7 strand of holiday lights will
cost approximately $33.75 in electricity
A standard strand of mini lights will cost
approximately $2.30
A LED Strand will cost approximately $0.27