As has already been said, the taxes, fees, or whatever are added to the base cost and cost per KWH, so all I really care about is the final total cost. We just have a small (1292 sq. ft.) house, but sometimes also run the window unit HVAC with heat strip in the 500 sq. ft. shop. TXU Energy has different plans available for different lengths of time, some with an early cancellation fee, some without. This last Fall they were going to raise my rate to more than 14 cents per KWH but I found and signed up for a 9 month plan at 10.4 cents. So my rates do tend to change about once a year. And of course our bills are usually higher in the heat of the summer but lately the cold weather has been increasing our bills. But I have a spreadsheet that shows the different total costs:
Year of 2011 - monthly average bill $200.45 - $0.13303412 per KWH
Year of 2012 - monthly average bill $152.73 - $0.11308200 per KWH
Year of 2013 - monthly average bill $160.35 - $0.10920152 per KWH
Year of 2014 - monthly average bill $210.65 - $0.10808107 per KWH (of course only one month of 2014)