While most people are captivated by the high-tech nature of solar electric PV systems, in most cases, a solar hot water system will harvest more energy at a substantially lower cost. In fact, compared to PVs, solar hot water collectors are more than three times as efficient at producing energy from the sun.

Investing in a solar hot water system is a smart solar solution for most homeowners. This proven and reliable technology offers long-term performance with low maintenance. And with federal, provincial, and utility incentives available, these systems offer a quick payback—in some cases, only four to eight years. A properly designed SHW system could provide all, or at least a significant amount, of your household hot water needs for some portion of the year. To get the most for your money, you´ll want a properly sized system that offers the best performance in your climate.

In this active, closed-loop system, incoming potable water is routed to the solar storage tank, but never into the collectors (either evacuated tube or flat plate). A water and antifreeze mixture circulates from the collectors (either evacuated tube or flat plate) through a coil in the solar tank or a heat exchanger, and then is pumped back through the collectors (either evacuated tube or flat plate). In most climates, a 50/50 propylene glycol and water mixture will keep collectors (either evacuated tube or flat plate) from freezing. The potable water is warmed by heat transfer through contact with the pipe.

These systems require an expansion tank and a few other auxiliary components for filling, venting, and maintaining the system. A definite advantage to antifreeze systems is that the collectors can be mounted anywhere. These systems are pretty much the only choice in very cold climates.

The following illustration includes the primary components of any pressurized glycol system.