is it o.k. to turn off my UPS at night?

Hi there,
I have my Mac Pro and various ext. hard drive setups plugged into an APC UPS... I got this particular UPS on the advice of various gurus on this forum, and it seems to work very well.
But I need to cut my electricity bill. So my question is, can I turn this UPS off at night, when my MP is off? I should say that I don't live in a part of the country where electrical storms are common, especially as we head into winter.
Thanks for any advice,
malch