Seems to me you would measure (and report) energy consumption in kilowatt hours or something, right? Not in dollars? At least, you would explain how you calculated the increased costs with some background detail...wouldn't you?
After all, I think energy costs were up at least "1% to 4%" over the time period discussed. Increased "bills" don't equal increased "consumption".
Finally, I don't know whether you can use 2 counties prior bills as a control for statewide weather patterns, and thus variability in consumption patterns across the state. Her results would only be interesting on a county by county basis.
In other words, localized weather conditions SHOULD have produced disparate results in various counties. The effect of GENERALIZING results across the entire state obscures the facts...