How does your filter look? Have you changed it? Have you taken the water hose to your condensor....15 degree air is not very good... Also cooling your home from 85 degrees to 78 degrees when it is hotter than Heck outside uses more electricity.

Have you looked at your meter every month..
Last month my bill was over 300 dollars ...said I used almost 4000 killowatts...
This month I used 2200 killowatts and the temps have been hotter...I believe they misread my meter last month, or they estimated.

My ac is at 72 degrees and with the temps in the 100s and the humidty being higher, it has trouble keeping up.

But when the temps are in the 90s, it works fine....
Central Air works by removing the humidity from your home...So it does work harder when it is more humid.

If you haven't cleaned your outdoor coil...well that could be your problem...
We clean ours at the beginning of the year and then after the cotton wood gets done falling...Another thing...When mowing...make sure your condensor is not running..
Just a few tips...I know that we have a high electric bill, but it is always higher Summer and Winter...We do not conserve as well with 2 computers and huge tv...lol
But I about freaked out last month....
This month even with the 10 100+ days we have had, it will be less than 200.00.

Also another thing...You may think that your ac uses so much electricity because of the difference in your bill summer/winter...What really is happening, is that electricity cost more in the summer...
You can go to OGE.com and see your bills and compare killowatt usage..