How much attention do you pay to your bills? Do you go through them line by line? Do you save the invoice? I drive my wife bonkers because I save all of the invoices from every bill. I also go through them line by line. I've gotten into the habit of scanning the invoices and destroying the originals to save on stored paper in the house, but at any time I can go through our old bills and make comparisons.
I'm also a nut for maintaining a budget in our house. I know how much to expect on a bill for any given period, and when a bill is off from that expectation I go through it line by line to find out why. Our cable and internet bill is usually the one that gets the most attention as I'm always watching for those introductory discounts to fall off. I was a bit surprised over the course of the last year to find that the Indianapolis Water bill was also fluctuating in seeming erratic fashion.
For those of you in the Indianapolis area serviced by Indianapolis water, go take a look at your bill. You'll notice that there are a few factors that make up your bill: a base rate, volume of water used (in 100's of cubic feet), rate applied to that volume usage, and a tax percentage. The Indianapolis Water utility folks come out from time to time and take a look at the meter leading into your house to get a reading on how much water you have used. They don't do this every month, so you may notice some bills marked with an 'E' to indicate that the volume usage was estimated for the month, and that the next month they will come out for a proper measurement.
Over the course of the last year I've noticed a significant increase in our bill. I was curious why: were we using more water, had the rate gone up, or was it some combination of both. I naturally suspected that our summer bills would be a bit higher as we watered the lawn and filled the inflatable pool for the kids, but I was very surprised to see that our winter bills were higher than those from the summer. What was going on?!
I went through all of those saved bills (huzzah!) and made a spreadsheet looking at our usage and costs throughout the year. Here is what I found:
This chart shows our bill from 01/30/2009 through 02/25/2010. For the first half of 2009 the trend was fairly level, but then we see that increasing trend, even through the winter. That concerned me. So what about my usage?
Well, that explains part of it. Our usage did go up through the winter months. I have a couple of theories on that. One, we have three kids, and in August our youngest hit the one year mark. Three young kids get dirty, no matter what time of year, and that means lots of baths. It also means lots of laundry and lots of dishes. So this could conceivably account for our usage increase. Still, our bill increased by nearly 50%, while our usage only increased by around 30%. Where did the additional cost come from? The Indianapolis Water bill indicates the base rate (what you pay regardless of how much water you use), but does not indicate the usage rate (what you pay for each 100 cubic feet of water). So I charted those as well.
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Yuck, our base rate went up by about a dollar each month.
Whoah, and we had a 20 cent increase per 100 cubic feet. Double whammy!
So that explains why my bill has increased: increased usage coupled with increased base and variable rates. All together, the bill breaks down as follows:
| Item | Jan 2009 Rate | Jan 2010 Rate |
| Base Rate | $8.21 | $9.10 |
| Cost per 100 cubic feet | $1.82 | $2.02 |
| Tax | 7% | 7% |
The only part of this bill that remained constant over that period was the tax rate of 7%. I'm still curious why the base rate and variable rates fluctuated from May through September of 2009. I would have expected a clean cut-over from one rate to another, but instead we see it bobble up and down until it settles on a rate in October. Have you noticed similar behavior in your bills?
An interesting bit of trivia - Indianapolis Water provides the water, and Hamtilton Southeastern Utilities takes care of sewage. In this same period, my Hamilton Southeastern Utilities bill remained a constant $33.55.