The last aspect to consider when buying a space heater is design. There are many designs of electric heaters, and there are many types of electric heaters. The different heat sources of the heater have a lot to do with the design. There are many different designs of electric heaters. Some of the most common shapes are square or round. Propane and natural gas heaters are usually rectangular. They are usually smaller than electric heaters. Infrared heaters are also usually rectangular or square. The design of most best electric space heaters is more functional than aesthetic, so there are not many attractive models. Oil space heaters usually look like accordions. Most original heaters are operated by oil.