 Some ideas for what you can do to cool down your house at little or no cost come from the Energy Trust of Oregon. Cameron Starr suggests pulling down window shades during the hottest part of the day, reduce your use of heat-generating appliances like ovens, and check the filters on your air conditioner, especially if it's a window mount or a portable unit. You want to make sure that you're checking those filters. And a lot of manufacturers state to check and clean those every two weeks. And if you've got pets, you probably want to increase that cycle.