请将下面一段英文翻译 China is now home to 27 million rooftop solar water heaters. With nearly 4,000 Chinese companies manufacturing these devices, this relatively simple low-cost technology has leapfrogged into villages that do not yet have electricity. Besides the attractive feature of paying no cost for your yearly eater energy consumption, the cost of installing one of these systems is priced at only a few hundred US dollars. That cost can be recouped by the average house in as little as a few years. It’s no surprise then that nearly 10% of all homes in China currently have a unit on their roofs along with a high year growth rate.