There are two types of solar heating systems appropriate for cold climates: glycol and drainback closed-loop systems. We chose to use the drainback system because it best fit our application. Rather than explain this system myself, I think this is the best internet site to begin learning the details involved in it. Our system is essentially designed on the same principals found at this site. However, our system only has one tank, which acts as both the drainback tank and the storage tank.
The article found at the referenced link explains that a drainback solar water heater is not able to provide 100% of the hot water we will need. So we have paired our system with a tankless heater. This will provide any additional heat we may need on the coldest and cloudiest days in Torrey.
For us, the negative aspect of this whole system was the type of solar panels we could use. As you can see, they are big and architecturally unattractive. The fact that we will ultimately use minimal propane for heat resulting in very small utility bills, will make them more and more attractive as time goes by. With a closed-loop glycol system, it is possible to use panels that can be mounted flush with a roof, but the glycol system appeared unworkable for what we needed.
I did have to laugh a little when reading one internet site that said, "... the drainback solar system is relatively cheap and simple to install and maintain." I'm just not quite sure what it's cheap relative to.