I got curious a few years ago so a created a simple Excel spreadsheet. It has columns: "READ DATE", "KWH USED", "DAYS", "KWH/DAY", "BILL TOTAL", and "COMMENTS". The only formula is dividing the 2nd column entry by the 3rd to get my average daily usage. Some of the notes are about previous bills being estimated, use of A/C and swapping 6, 13W CFs for 60W incandescent bulbs in the kitchen. I could see a difference from the CFs. I also noticed the increased consumption from firing up the humidifier. That's when I switched to using 2 decorative fountains and one I built for my little girl, and plants to add moisture. Now, I tend to use 8 to 10 KWH per day until A/C season, when I get into the mid to upper 20s. My highest average was 39.61 KWH/DAY but I have a comment that the previous bill was estimated. I think everyone should do something like this because it is easy to just open up the spreadsheet and enter the numbers on the day you get your bill.
Joe
