Operating Hours vs Sun Hours

On a HelioScope report, at the bottom of the Annual Production table, users will see a metric that says Operating Hours. Typically, this value will be 4600 or greater, but what exactly is operating hours?

In HelioScope, any hour window with sunlight counts as an operating hour. That means that whether the sun rises at 8:01 or 8:59, both of those will count as some sunlight falling in the hour window from 8-9 am. That doesn't mean there are 4600+ hours of full sunlight, but there are that many hours in which some irradiance is falling on the panels.

This can be easily confused with the industry metric of Peak Sun Hours, which refers to the hours of sunlight a location would receive if the sun were shining at its maximum value only.

Sun Hours per day can be calculated using our CSV File:

  • by taking the annual GHI, then divide it by 365  and then by 1000 to get the sun hours. Dividing by 365 allows us to find the average daily GHI. Since GHI in the CSV is measured in watts per square meter, and Sun hours are measured in kilowatts per square meter, dividing by 1000 converts to give us our final value.
  • Example: 2,146,000/365 then divided by 1000 = 5.9 Sun hours