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Land and site · Study the site: sun, water, wind and soil · site-5

Map the sun path and shading

Measure where and when the site gets direct sun through the year so you can place the house, solar array, greenhouse and garden where shade will not cut output.

How

  1. Get a sun-path chart for your latitude and longitude. Charts from within about 50 miles in the same time zone are generally close enough.
  2. Use a shade measuring tool (for example a Solar Pathfinder, a fish-eye shade analyser or a smartphone app) at each corner of each candidate array and building location.
  3. For any single obstacle, its elevation angle is arctan(height above the panel or window / horizontal distance). Compare this with the lowest sun altitude in your chosen shade-free hours.
  4. Decide your shade-free window. Peak PV hours are around 10 a.m. to 2 p.m.; a wider 9 a.m. to 3 p.m. window needs much more clearance.
  5. Allow for tree growth and future buildings, which can block the sun years later. Use the shading clearance calculator in this module.
  6. Mark best solar zones on the base map overlay.
  7. Quick check without a chart: the noon sun altitude is about 90 degrees minus your latitude at the equinoxes, plus 23.45 degrees at the summer solstice and minus 23.45 degrees at the winter solstice (solar declination ranges between about plus and minus 23.45 degrees). Use the winter figure as the worst case in the shading calculator. Morning and afternoon sun is lower, so a sun-path chart is still needed for a full shade-free window.

Do these first

Sources

  1. Solar Orientation: Solar Arrays and Panels. Pacific Northwest National Laboratory, Building America Solution Center (US DOE), accessed 2026-11
  2. Solar Site Evaluation (SolarPro magazine reprint). Solmetric / SolarPro, accessed 2026-11
  3. ARCH 125/366 Environmental Design, Chapter 6: solar geometry (course notes credited to Prof. Leonard Bachman, University of Houston). Terri Meyer Boake, course materials, accessed 2026-11
  4. EME 811, 1.2 Solar Geometric Angles. Penn State University, John A. Dutton e-Education Institute, accessed 2026-11

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