Don't have any outdoor space? Try dryer balls.
As I first got them from our son as a result of a energy saving school project, I was rather puzzled. But I have to say, they really make a difference. I was not standing in front of my dryer stopping the time, but I noted a distinctive shorter running time when the balls where in there. Also fleece items seem to be fluffier with the “ball drying” method.
What are dryer balls? Well, meanwhile you can buy all sorts of plastic dryer balls in stores, but the original dryer balls are soft wool felted balls that you put in the dryer with your wet clothes when you start the drying cycle. The balls bounce around lifting and separating the clothes, allowing the hot air to flow more efficiently. This makes the drying time shorter and therefore you use less energy. If you use 4 balls in the dryer at one time you can cut an average of 25% off your drying time. Our son recommends using 16, so you would save 100%.......
How to make dryer balls: You will need 100% wool yarn, preferably light colors to prevent initial bleeding. It needs to be relatively unprocessed wool, so no super wash or acrylic mix wool, since you want the ball to felt.
Make the core: Wind the wool tightly to a about golf size ball, secure the end and put it in a sock or nylon stocking, knot the sock tightly and wash and dry this a couple of times in your hottest cycle. If you do multiple balls at once, make sure to separate them in the sock or stocking by tying a band around the sock between each ball (looks like a caterpillar).
Finish the ball: Once your core is nicely felted, wind more wool around it, until it has the size of a tennis ball, secure the ends and repeat the sock/washer/dryer exercise. Take the sock off and your dryer ball(s) are ready to use.
I used my original ones for about a year before they were starting to fall apart, but since I have enough wool scraps, I just made myself new ones.