O&M Services of PV Plants

The lifetime of PV plants is 20 years. The continuous and systematic monitoring of the plant leads to rapid identification and immediate restoration of any problem that may occur to the equipment. Regular maintenance of the installation ensures slow equipment wear, safe operation of the PV plant and optimum efficiency which lead to higher economic return during the operation of the PV station.

Energy Efficiency has developed and offers the following operation and maintenance services.

Daily monitoring of the photovoltaic system

The aim of this service is:

  • Daily monitoring of the energy production.
  • Check of the inverter’s error and justification of the cause of the problem.
  • Monitoring and comparison of the output of each inverter separately.
  • Identification of the reason of a malfunction and suggestion of ways to resolve it.
  • To provide monthly report of the PV plant’s performance and list of the occurred errors in the installation.
  • Energy study of the theoretical expected output of the plant and comparison to the actual energy production on a monthly basis.
  • Solutions for optimizing system’s performance in a case of performance deviations.
  • Report of errors and activities within the year.

Annual preventative maintenance of the PV plant

The aim of this service is the preventive maintenance of the plant in order to check the correct operation of the PV station. A set of measurements, checks and works are realized regarding the installed equipment in accordance to manufacturer’s specifications. In more detail:

  1. Maintenance of the low voltage (twice per year)

PV modules

  • Visual inspection of PV modules in order to detect if there are broken or cracked PV modules and whether there is need for cleaning.
  • Inspection of possible shading of photovoltaic panels during the hours of maximum yield of the park.
  • Sampling check of the clamps of photovoltaic panels on the mounting structures.
  • Measurement and check of the photovoltaic panels by measuring annually the I-V curve during the summer measurement.
  • Measurement of the open-circuit voltage (Voc) and the short circuit current of each string annually during the summer measurement.
  • Measurement of the maximum power point operation voltage (Vmpp) and the maximum power point operation current (Impp) in order to detect disconnected strings during the operation of the PV plant.


  • Inspection of the visible routing of DC & AC cables.
  • Inspection of exposed cables to weather conditions.
  • Inspection of the existence of visible wounded cables.
  • Inspection of the cable tightening in the DC & AC boards of the installation.
  • Measurement of the insulation resistance (Riso) of the cables on string level annually during the summer measurement.

Mounting structure

  • Visual inspection of the mounting structures for signs of damage or subsidence.
  • Visual check of the tightening points of the grounding and inspection for potential corrosion.
  • Measurements of grounding continuity in inverters and PV modules.

DC & AC boards

  • Check of tightness and damage existence.
  • Anticorrosive protection and cleaning the inside of the boards.
  • Inspection of the DC fuses and replacement of the burned ones.
  • Visual inspection of the installed lightning protection if there is any.
  • Calculation of short-circuit current (Isc) and checking of the rightness of the dimensioning of the installed fuses if there are any.
  • Propose ways for optimization where damages or deficiencies are detected.


  • Check of the operation and the software of each inverter.
  • Software upgrade if necessary.
  • Inspection and maintenance of inverters based on the instructions of the manufacturer.
  • Visual inspection of the tightening of DC and AC cables that terminate to each inverter.
  • Background check of failures of the installation whether it is possible.
  • Check of the dimensioning of the inverter based on the standards of the manufacturer and check of its installation.


  • Inspection of the operation of the monitoring system, inspection of the good communication with all the different parts of the PV plant and data transmission via internet.
  • Visual inspection of the communication cable and the visual routing of the park.
  • Upgrading software of the monitoring system if necessary.


  • Thermography of the equipment and the cabling of the installation by using thermal camera if necessary or in a case of a problem have been reported earlier in the installation.

Technical report

  • Creation of technical report for each intervention in the PV plant recording all the performed maintenance work, the used materials and the comments about the operation of the PV plant.

Back office services

  • On our customers we provide free back office services with phone technical support on their questions based on the operation of their plants. The services are offered on working days and hours (Monday – Friday from 9:00am to 5:00pm).
  1. Maintenance of the medium voltage station (once per year)
  • Cleaning of the medium voltage station and transformer using vacuum cleaner and disposal of unnecessary equipment from the station.
  • Thorough cleaning of the transformer for the avoidance of arcing on the connectors.
  • Thorough cleaning of the low voltage station. The cleaning is done using vacuum cleaner and brush.
  • Inspection of the cooling of the transformer.
  • Inspection of the oil temperature and the indicators of the thermostat.
  • Grounding inspection on the medium voltage station.
  • Oil leak inspection on the transformer and restoration when possible.
  • Oil level inspection on the transformer.
  • Έλεγχος στάθμης λαδιού Μ/Σ.
  • Medium voltage insulators inspection.
  • Inspection and cleaning of the medium voltage panels.
  • Optical inspection of medium voltage cabling.
  • Inspection of safety instruments of the station.
  • Checking if there is need for oil testing.
  • Inspection of transformer fuses.
  • UPS inspection
  • Station lights inspection.
  • Fire system inspection.
  • Creation of technical report for each intervention in the PV plant recording all the performed maintenance work, the used materials and the comments about the operation of the PV plant.

Interventional maintenance of the PV station

The aim of this service is to detect and provide all the necessary actions in order to resolve within 48 hours any potential problem that might arise during the function of the PV plant.