I just got my PG&E bill and I was shocked. Last month it was $55 because I wasn't home for the whole month which is pretty much my pattern. But this past month I was home the whole month and it was a hot one, 100+ temps almost every day. This months bill was almost $200! Yikes. My question is which is better, closing vents in rooms I don't use or leaving them open or it doesn't make any Difference. I have 3 bedrooms closed that I never use and also one bathroom. In my 2,000 sq ft house I use about 3 rooms. Which way would be more cost effective?