UTF-16 uses 2 to 4 bytes to encode each symbol. However, a UTF-16 file does not always require more storage than UTF-8. For example, Japanese characters take 3 to 4 bytes in UTF-8 and 2 to 4 bytes in UTF-16. So, you may want to use UTF-16 if your data contains any Asian characters, including Japanese, Chinese or Korean. A noticeable disadvantage of this format is that it's not fully compatible with ASCII files and requires some Unicode-aware programs to display them. Please keep that in mind if you are going to import the resulting document somewhere outside of Excel.