Originally Posted by obimark
... that gets MUCH louder at night only... I am on the second floor of my house ...
Are there street lights outside your window?
I have the same problem, albeit in an older house (and older wiring). During the day, I get very little, if any, interference. Come night-time, depending on which bass I'm playing, the static noise can get to where it's no fun playing. So, an old house/wiring and a ceiling fan/light with dimmer switch are the constants. IMO, the one primary variable that changes are the street lights. It could also be that with more people home at night instead of at work/school/etc., there is more of a draw on electricity in your home depending on what they're all doing.
Do you have a bass w/ humbuckers? I found that using either my Music Man or my former Lakland 44-02 would tame the noise. Forget it using my jazz or P bass with single- or split-coils.