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Off-grid PV systems

This part of PVGIS calculates the performance of PV systems that are not connected to the electricity grid but instead rely on battery storage to supply energy when the sun is not shining. The calculation uses information about the daily variation in electricity consumption for the system to simulate the flow of energy to the users and into and out of the battery. The calculations are made with the full temporal coverage of the solar radiation database chosen.

The tool can be accessed with:


The output consists of monthly average values of PV system energy output and probability of battery charge reaching full or empty state. There is also a list of 10 values giving a histogram of battery charge state. Some additional information about the calculation is also supplied in the output.


The header of the output contains the following information restating the input parameters, each on its own line:

  • Latitude (in decimal degrees)
  • Longitude (in decimal degrees)
  • Name of the solar radiation database used
  • One empty line
  • Slope (inclination, in degrees) of modules
  • Azimuth/orientation (in degrees from south) of modules
  • Nominal power of the PV system (in W)
  • Battery size (Wh)
  • Discharge cutoff limit (%)
  • Consumption per day (Wh)

This is followed by a blank line and some general numbers about the calculation:

  • d_total [d] - Number of days used for the calculation
  • f_f [%] - Percentage of days with fully charged battery
  • E_lost [Wh] - Average energy not captured due to full battery
  • f_e [%] - Percentage of days the battery became fully discharged
  • E_miss [Wh] - Average energy missing

After this follows monthly values for the energy output and the battery state. There is one line of header followed by the data with one line per month, and the columns given by:

  • month [number]
  • E_d [Wh/d] - Monthly average energy production per day (Wh/day)
  • E_lost_d [Wh/d] - Average energy not captured per day (Wh/day)
  • f_f [%] - Percentage of days when battery becomes full (%)
  • f_e [%] - Percentage of days when battery becomes empty (%)

At the end of the table there are a few lines of explanation of the fields.

The second table in the output gives the probability of charge states for the battery. This part consists of one line of header followed by 10 lines with the following information:

  • CS [%] - Range of charge state, in percentage
  • f_CS [%] - Percentage of time when the battery had this charge