The system is working well. The solar system can collect up to 2 days worth of hot water on a good day. The storage tank can 'hold' about 5 days worth of hot water. Therefore with sustained sunny weather the tank temperature gradually increases and we can sustain poor sun days without resorting to the wood backup. During the heating season, wood will be the primary fuel, however any solar heat added to the system will offset wood use.
As wood has been our only fuel before adding the solar, we had to run the wood boiler once every five or six days in the non heating season in order to provide hot water. Since adding the solar component we have only rarely used the wood boiler in the non heating season and then only after a period of sustained cloudy weather.
Latitude51 Comment: Note this system used a Bubble Pump (see top right corner of the photo with the collectors, its an off grid system, uses no electricity to pump the water and has no moving parts.)