As we hit the warmest months of the year, it’s a good time to remember that cooling down an apartment can really heat up energy bills. Luckily, some of the easiest ways to lower cooling costs are also some of the least expensive. Just keeping blinds and curtains closed during the hottest parts of the day—usually between noon and 6 pm—is amazingly effective in keeping heat out. Bonus efficiency points for getting lighter-colored curtains, which reflect heat. Black-out curtains also provide extra protection because the tightly woven fabric won’t let the sunlight through. Of course, if the blinds are closed, that means more lights will probably be on. Make sure fixtures have cool, energy-efficient bulbs like LEDs. They’ll produce less heat than regular bulbs and require a lot less energy for the same amount of light.