Safer and more convenient than many of their alternatives, patio heaters have emerged as a backyard favorite that enables family and friends to enjoy the outdoors day or night, even when the temperature drops. The most powerful heaters run on cost-effective propane. Take, for example, this heavy-duty powder-coated model from AZ Patio Heaters. At 41,000 BTUs, it radiates a 10-foot diameter of heat. And when the season is over, simply roll the wheeled, portable unit into storage. Available on Amazon; price varies by finish.