I was told that I need to mount the collectors due south at the same tilt as my latitude to get the most efficient system. Is that right?

While I have heard this statement a number of times it misses the mark. Frequently a homeowner will have a roof that is not ideal for collecting solar energy. The roof might be east or west of south and have a pitch that doesn’t match the latitude. Rather than discouraging the homeowner from pursuing solar we should be educating them so they know how much energy they can produce. For example, a 4 person home in Raleigh, North Carolina with 2 of our platinum collectors and an 80 gallon tank would receive approximately 73% of their hot water from the sun. If you take the same demand and mount the collectors flush on a 5/12 (23 degrees) roof the system would produce 72% of the families hot water needs. The same is true if the panels are mounted on a 12/12 pitch roof. So the angle of the collectors is fairly insensitive to the angle the collectors are mounted for a year round hot water systems overall performance. What about the angle of the collectors? If you take the same two panel system and point it south-east or south-west you would only reduce the annual output to 70% of the families hot water needs. If you went so far as to point the collectors due east or west you would only reduce your solar fraction to 62% of the families hot water needs. As you can see solar water heating systems are fairly robust when it comes to placement and performance. There is rarely a case where the performance of a system would dictate mounting the collectors at a funny angle. So the next time you are asked about installing collectors on somebody’s roof that doesn’t match the perfect profile. Don’t sweat it.