Hypothetical solar hot water system calculations

Here is how a hypothetical 2-panel system would perform at the center of the lot at ground level. The calculations are based on the shade analysis from the Solar Pathfinder (images available on an earlier post).

Btu gain - 64 dgr tilt

If one is interested in maximizing one’s wintertime gain, a 64 degree tilt is optimal. One can confirm this with the online program PVWatts 1 by plugging various tilt angles until arriving at the most wintertime energy gain.

2 Panel - SHW - 64 dgr tilt - winter analysisThe calculations show that the system will output on an average winter day about 49 gallons of hot water.

A comparative analysis:

Solar hot water summarySince we will need the most hot water during wintertime, it makes sense to tilt the panels to 64 degrees. Of course, if these were photovoltaic panels (generating electricity) this would not at all be the way to go.