This is actually a tricky question, because you can only answer it if you know what is normal or average. The first step is to look at past bills over the years and note any changes. Did the bill increase because you have an additional roommate? Did you install new equipment that needs plenty of electricity or are you now using a room you didn’t heat/cool previously?
If the answer to these and similar questions is no, you should look at the rate. Did your energy provider increase prices? Did your agreement change in any other way or are you not eligible for rebates anymore?
If all of your answers are still no, you could look at seasonal changes. If your utility bill has increased during the winter months in particular, the heater might need to be fixed or replaced. If your utility bill has increased during the summer months, your air conditioning might become less cost-efficient due to age or damages. Having the suspects inspected is certainly good advice in this situation. Your local Heating and Air Conditioning expert will help you find the culprit and propose a solution.
Another way of looking at this issue is to compare your bill with friends that live in similar circumstances. These circumstances would include a comparable insulation of homes, similar age and efficiency of windows, doors and furnaces, and very similar heating/cooling habits, though. MidAmerican Energy can help you out with free energy audits in this regard. If your friend’s bill is indeed 20% or so lower than yours, the problem might be a rather fundamental one. Typical suspects are insufficient insulation and old equipment. The solution might be as simple as closing a hole in your ducts. In any case, this is a great opportunity to get informed about insulation and new energy-efficient equipment that can save you money in the long term.
One more way of looking at the issue is to analyze your heating/cooling habits. Are you keeping temperatures the same during the night, although this isn’t necessary? Are you leaving the house in the early morning and return to a freezing home during the summer and a hot home during the winter? A simple change in habit might do the trick and can even be complimented by an automatic thermostat.