MURPHY SUCKS!!!
I'm not too knowledgeable in these things, but I think those who are would benefit from more info, such as type of heat source, fuel, delivery, square footage, age of home, etc.
As far as AC goes, if you use it regularly, updating will pay off eventually, as there are more efficient options. From the fact that you specify AC and heat in the same job, I'm presuming you have forced hot air. If you are using oil, and natural gas is available, switching would be something I would do. Also, consider some of the dual fuel furnaces, that can burn wood (and some will do wood and/or pellets) and oil or gas/LPG. That way you can offset some of your heating with wood, but still have the convenience of a thermostat controlled central heat source. If my newly purchased home didn't already have a 5 year old Williams oil furnace, I'd certainly do this myself.