You mean electric auxiliary heating. If you use in the Xinjiang region, use ultra-low temperature heat pump, now seems to have -40 degrees can work. This does not use electric assisted heating, electric assisted too much power consumption, electricity can buy a machine. I do not know whether you are in the southern or northern border. Specifically what to do with the specific location before you can check the solar power distribution map.
Solar energy resources in Xinjiang can be, but during the day can, so add insulation tank.