I live in an apartment but my landlords are less than responsive. I'd like to have an idea what the issue is when I confront them. When I moved in I noticed that the heat would run for a long time just to gain a degree or two. So I changed to a more expensive thermostat and stuck weatherstripping everywhere I could think of. This helped very little because as soon as the temperature dropped to the level that I had the heat set to kick on, it would take an hour or more just to gain the 2 to 3 degrees it would take to kick back off. I have been dealing with $200 electric bills in an apartment. Now that the weather is warm, I was hoping my problem would go away. But the A/C is doing the same thing. Just to get the temp to go down to a tolerable level takes at least an hour and my bills are still outrageous. What could be to blame for the unbelievable inefficiency I am experiencing in heating and cooling?

Did you check the air filter? Usually these types of problems are caused by bad duct design

Yes. I put a new filter in once I started noticing the problem. I also changed the thermostat. Could the problem be in the duct work that I can't see?

Yes that is probably a good guess. Lots of times people do not install big enough or just enough return airs