Does a solar water heater freeze in winter?  
  The water tank is well insulated. The National Solar Lab test results show that overnight the IP-195 unit loses 1°C for every 6.43 degrees difference between the tank temperature and the air temperature. It loses less energy during a night than it picks up during the day, even in a cloudy or snowing day (See Fig. 1).  
  Heating cables are installed and applied with the plumbing lines outside of the house to keep the lines warm in the winter time. It is automatically controlled by a controller (See Fig. 2).  
  In the GTA, there are now over 300 units of IP-195 working safely and no winter issues, with the earliest serving five winters already.  
Figure 1. Well-insulated Water Tank
Figure 2 .Heating cables