Live in an apartment? Need to use an air conditioner to stay cool? Wondering how to be environmentally friendly and save energy without sacrificing cool air? Here are some tips and ideas to consider:

1. Look for a green apartment.

As an apartment dweller, you unfortunately cannot make all the environmentally friendly changes such as adding insulation or buying a more efficient HVAC system that someone who owns their own home may be able to do. However, you can mitigate that restriction by choosing your apartment carefully.

If you are in the market for a new apartment, check the building's rating under the Green Building Country of Australia. Its Green Star Multi Unit residential tool shows you the efficiency ratings of new apartments. If the apartment is too old to have a rating, look for things like convective ventilation that helps to bring in cool air on lower levels and release hot air at upper levels. Alternatively, ask the building manager about the efficiency of the building's HVAC system.

2. Choose your air conditioner carefully.

Whether you are trying to cool your existing apartment or a new one, if you are buying a portable air conditioner or a unit that goes in your window, choose it carefully. Most units clearly say on the side how much space they are designed to cool. If the unit is overpowered, it will waste energy every time it runs, and if it is underpowered, it will run constantly, trying to cool the space, which also wastes energy.

3. Consider cooling just one room.

Rather than cooling your entire flat, consider cooling just one room. Whether you choose your living room or a bedroom, keep the door of that room closed so that the AC doesn't try to cool the rest of your home. To keep air circulating through the rest of your apartment, consider using fans -- they use less energy than air conditioners.

4. Invest in insulated window treatments.

One change you can easily make to your apartment is to buy insulated curtains. Window treatments support your AC because they help to keep the cold air inside. They also act as a layer of insulation preventing the hot air hitting the outside of your windows from penetrating into your flat.

5. Arrange your furniture strategically.

Finally, look at how your furniture is arranged. Make sure you don't have furniture blocking the AC, and orient the furniture you use the most so that it's facing the air conditioner. That allows you to get the most cooling benefit with the least amount of energy possible.