A.M.
We have Reliant and have been very happy. I have a 1750 sf home and our bill this last time was only $93. Granted, we have a very effecient new A/C unit (just put in last year) and a new roof that has a reflective coating on the inside of decking (reflects the heat out of the attic). And I keep the house at 78 during the day (we're home then but it's not hot at all at that setting)...during nighttime sleeping i keep it at 74....and it's cold then! brrr...but we like it cold when we sleep.
I would not only shop around for different prices...(ask about year-long contract rates -- those are cheaper..but there is a penalty if you cancel/switch energy providers during that year)....but I would also look into different ways to make your home more energy efficient. Get your A/C unit serviced/cleaned ...sometimes that can add more efficiency to it. Look into adding insillation to your attic....are there areas of the home where too much heat is coming in or too much cold air is escaping??
My brother has a new home, built in 2002....and they just discovered last summer that his A/C unit was taking air from his attic and trying to cool that air down and push it out to the main home. ....A/C units are supposed to take air circulating from home and cool that down and funnel it to the main home. Anyway....that explained why his energy bills were outrageous. After an A/C guy came out and fixed that problem...his bills have been better, much better.
I think you can get an energy efficient evaluation done from an A/C company.