Home / Holiday How many light strings How many sets you can connect end to end, from the watts on your set's tag and the limit in its instructions. → Christmas light fuses Where the fuses are, how to change one, 3 A or 5 A, and when to throw the set away. → C7 vs C9 vs mini bulbs C7 or C9, the base each takes, and what to match on mini lights. → Indoor or outdoor lights Whether a set can go outside, the GFCI it plugs into, and the extension cord to use. → Half a string out What to check when part of a string goes dark, in the order GE gives. → Christmas lights cost What a set of Christmas lights costs to run an hour, a night and 30 nights, from the watts on its tag. → S14 string light bulbs The size and base of the S14 bulbs in patio string lights, LED or incandescent, and what to check on the string. → General guidance from manufacturer and standards data. Products vary, so check the label and the maker's instructions.