Tracking expenses

Lately, I've been playing around a little bit with Google Docs- there's some cool stuff there!

As ya'll know, I'm big on budgets. One of the keys to a successful budget is making it realistic. An unattainable budget is both frustrating and futile, and, for us, ends up causing more harm than good. A realistic budget takes into account what we actually spend on different categories now, and makes a reasonable projections to the future. Picking random numbers for budget categories, or basing my budget off of someone else's expenditures is meaningless, and ultimately will cause a budget to fail.
walk in tubs
Like I said, I've been playing around with Google Docs. Here, I have our expenditures on electricity over the last few months. Because we haven't lived here a year yet, we don't know what our "normal" May electric bill will be yet, but logging this year's bills will make us able to budget more accurately next year. This year, we're basing our budget after the previous owner's electricity usage in the house, which may or may not be very much like our own. Using our own numbers in the future will not only help us budget more accurately, but will let us see how our usage changes year to year! As a bonus, sticking the numbers from the energy company into a spreadsheet brought to light rate changes- the per-kWh rate seems to fluctuate month to month, and went up almost 2 cents on my last bill.

What do you learn by tracking your expenses?