How to Design and Size a Solar Lighting System

You Determine:

  • • Geographic Location:  Different geographic locations have different solar insolation which determines the size of the required solar panels
  • • The Application:  Different applications need different amounts of light 
  • • Light Level Requirement (if any): Different light level requirements may be required by city or county codes and will depend upon the pedestrian or vehicle usage of the project. 
  • • Run Time (Duration of the Load): Number of hours you need the lights to be on each night.  Examples: Dusk to Dawn, 12 hours, 6 hours, or one of our split time controllers (6/2 or 4/2 – 6 or 4 hours after dusk & 2 hours before dawn), etc.

We Determine:

  • • Sun Hours based on your location: Different geographic locations have different solar insolation (sun hour factor) which will determine the size of the solar panel(s) needed. 
  • • The Light Output: Based on the amount of light you need for your particular application or specific footcandle requirement on the ground 
  • • The Size of the Required Solar Panels:  Solar panels typically come in a variety of sizes. We always calculate a reserve and round up to the next higher panel size. 
  • • The Model – Flat Solar Panel Array or Tilted Solar Panel Array Based on your particular parameters, we can recommend which system will be more cost effective. 
  • • The Size and Number of Batteries: 
      • • Our systems are typically sized with 5 days battery back-up.
      • • Our Power Management feature monitors battery voltage and adjusts accordingly (LED models only)
      • •  Additional battery back-up can be added if needed. 
  • • The most suitable Fixture style: Cobrahead or Shoebox -- Drop lens or cut off lens are available. 
  • • Optimal mounting height, pole spacing and placement, to match your specified light requirements.

Performance of Solar Lighting Systems

The performance of solar lighting systems measure in foot-candles or lux on the ground.

These are influenced by:


  •  •  Type of light source
  •  •  Reflector
  •  •  Refractor or Lens
  •  •  Pole Height
  •  •  Spacing of Poles 

How to Scrutinize Projects for Viability

  • • Common Sense - Avoid Shaded Areas: Solar panels need the sun.  In heavily shaded areas, solar arrays can be mounted remotely to gain access to sun.  Be sure there is a clear southern sun exposure (live north of equator) or clear northern sun exposure (live south of the equator). 
  • • Check any lighting level requirements 
  • • Evaluate Required Operation Time(s): The longer a light needs to stay on, the larger the system, and subsequently the more expensive it is. 
  • • Determine Reliability/Security Issues: If security lighting is critical, our full dusk to dawn calculates your longest night in December (northern hemisphere) or June (southern hemisphere).

Comments (2)

Connie Nisen says:

Thank you for your information. I Believe with todays innovation and solar technology, that it is more specific to determine the productivity of solar energy. It used to be a guessing game as to how much energy is converted to usable power. Do you have data as to how much sunlight, be it direct or in a relatively cloudy region, how effective harnessing solar energy is?

mmcdermott says:


As mentioned above, our systems are sized based on many factors (no guessing involved - just simple math). For PV panels, the average efficiency is approximately 18% and our conversion efficiency is just over 90%, which allows us to effectively calculate the power generated by each panel.

There are a few more efficient panels available in the marketplace but they are very expensive and the cost to power ratio makes them prohibitive. Besides, it is more than just the conversion efficiency that must be considered - the ability to store the energy and then produce it on demand must be considered as well.

There are many websites that provide additional info in regards to PV harnessing and costs.
Here is a chart provided by the DOE about the cost of PV solar energy:

A great article by Sandia National Labratory:

A History of Solar from the DOE:

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