PERSONAL HABITS
Scrooge is described as not being frightened by echoes, double-locking himself in, and preferring darkness, which may indicate cautious or solitary personal habits. He also likes darkness because it is cheap, suggesting frugality.
SCROOGE
Scrooge was not a man to be frightened by echoes. He fastened the door, and walked across the hall, and up the stairs: slowly, too: trimming his candle as he went. Up Scrooge went, not caring a button for that. Darkness is cheap, and Scrooge liked it. ... double locked himself in, which was not his custom. Thus secured against surprise, he took off his cravat; put on his dressing-gown and slippers, and his nightcap; and sat down before the fire to take his gruel.