Solar Photovoltaic Auditing
Use this page when solar PV output, irradiance, inverter behaviour or site energy use needs to be checked with recorded data rather than estimated from generation totals alone.
Solar PV performance depends on irradiance, panel condition, inverter behaviour, DC and AC electrical conditions, shading, orientation and site load. Logging helps separate poor generation from normal weather variation or site usage patterns.
For a useful PV investigation, record the electrical output and the available sunlight over the same period wherever possible.
What to measure
- Solar irradiance over the logging period.
- PV DC voltage/current or DC energy where the DC side is being assessed.
- PV output trends compared with irradiance and expected site behaviour.
- Battery-system charge/discharge behaviour where storage is part of the system.
- Before-and-after proof after maintenance, cleaning, replacement or configuration changes.
Recommended loggers
| Product | Logger | Best fit | Measures |
|---|---|---|---|
 |
DC-3VA Electrocorder DC-3VA DC Energy Data Logger |
Best for DC energy and power behaviour in PV, battery and DC systems. | DC voltage, current, power and energy. |
 |
PV-3 Electrocorder PV-3 Solar PV Output Recorder |
Best for recording solar PV output and generation behaviour. | Solar PV output. |
 |
DC-3V-RS Electrocorder DC-3V-RS DC Voltage Logger |
Useful where the key question is DC voltage profile rather than DC energy. | DC voltage. |
 |
SR-1R Electrocorder SR-1R Solar Irradiance Recorder |
Best for recording solar irradiance so PV output can be compared with available sunlight. | Solar irradiance. |
Detailed guidance
What a solar PV audit is trying to prove
A solar photovoltaic installation converts solar radiation into DC voltage and current at the panels. The inverter then converts this into AC voltage and current for use on site or export to the grid. A PV audit is used when the system output appears low, inconsistent, or difficult to explain from generation totals alone.
The main losses in the system are usually in the PV panels and inverter. PV cell efficiency is often around 15% to 18%, while inverter efficiency is typically better than 95%. Overall system efficiency may be around 14% to 17%, but the actual result varies with equipment, installation, temperature, shading, dirt and weather.
Why output alone is not enough
PV output changes from day to day because of cloud cover, sun angle, season, ambient temperature and shading. Shading may also change through the year, for example when nearby trees have leaves. Panels can become dirty, individual cells can fail, and inverter performance may vary with temperature or installation conditions.
Because of these variables, generation totals alone do not always show whether the PV system is performing correctly. Meteorological records can help predict expected output, but when a system is already installed and performance is being questioned, there is usually no substitute for logging the actual irradiance and electrical output.
Measure irradiance and output together
The most useful PV audit compares the available solar energy with the electrical output from the PV system over the same period. This helps separate poor weather from poor system performance. If irradiance is high but output is lower than expected, the cause may be panel condition, shading, inverter behaviour, wiring, system configuration or another installation issue.
Electrosoft can use the system area and panel efficiency to help calculate expected energy input and compare it with measured output. This gives a more proof-based view than simply looking at daily generation totals.
Useful Electrocorder loggers for PV work
The PV-3 records solar irradiance, which is the energy input from the sun, and can also record DC voltage and DC current representing output from the PV panels. This allows panel efficiency and system performance to be assessed over time.
The DC-3VA records two channels of DC voltage and one DC current channel. It is useful where the electrical output of PV panels, DC systems or battery-linked installations needs to be measured over a period of time.
The SR-1R records solar irradiance. It is useful for assessing the likely energy available to a future solar PV or solar thermal installation, or for comparing irradiance with output measured by another logger.
How to approach the audit
Choose a logging period that includes representative weather and normal system operation. If the concern is seasonal shading, repeat logging may be needed at a different time of year. Where a fault or performance concern has been raised, record enough data to compare sunny, cloudy and variable conditions.
Review PV output against irradiance, temperature, time of day and site load where relevant. If maintenance, cleaning, inverter changes or configuration changes are made, repeat the logging afterwards so the improvement can be confirmed.
How to approach the investigation
- Record irradiance and PV output over the same time period where practical.
- Compare good-weather and lower-light periods rather than relying on a single reading.
- Check for patterns that suggest shading, inverter clipping, battery behaviour or unexpected load changes.
- Use before-and-after logging when maintenance or changes are made to the PV installation.
Related guides and products
These pages and products give the next level of detail for this application.
Application guides:
- Solar PV, Battery Storage and DC Loggers: for solar irradiance, PV output, DC voltage/current and battery-system studies.
- Energy Audit Loggers: for energy audits, load profiles, peak demand and before/after savings proof.
- All application guides: choose an Electrocorder by the job or problem you need to investigate.
Relevant products: