# Solar Power Plant Monitoring: Catching Lost Generation at Inverter and String Level

> What solar plant monitoring should measure: inverter, string and irradiance data, performance ratio (PR) tracking to catch losses early, and a 7-step plan.

Source: https://digitalbridge.com.tr/en/blog/solar-plant-monitoring.html
Publisher: Digital Bridge Teknoloji (https://digitalbridge.com.tr)
Topic: Industry 4.0
Published: 2026-10-26 · Updated: 2026-10-26

Solar power plant monitoring is the hardware and software that collects inverter, string, meter, irradiance and module temperature data every few minutes, compares actual output with what the plant should be producing under current conditions, and raises an alert when the two diverge. The goal is to spot lost generation the same day, not at the month-end meter reading.

## Key takeaways

- Solar power plant monitoring collects inverter, string, meter and irradiance data every few minutes and compares actual output with expected output.
- Performance ratio (PR) is the most useful health indicator because it accounts for irradiance; the IEC 61724 standard sets its framework.
- Measuring at string and inverter level separates slow-building soiling from a single blown fuse or inverter fault.
- According to Türkiye's Ministry of Energy and Natural Resources, 22% of the country's installed capacity was solar at the end of August 2026.
- Inverters from different brands are merged into one data model over open protocols such as Modbus; set-up starts with a single-site pilot.

## How lost generation hides on a solar site

Output on a solar plant can drop quietly while everything appears to be working. The inverter maker's portal shows the unit as online, but a blown string fuse, a loose connector or a shaded row on one of its inputs shows up only as a small dip in the total. In a cloudy week that dip gets blamed on the weather and nobody visits the site.

Some losses build slowly. Soiling on module surfaces, especially in dry and dusty spells, trims output a little more each day. On sites with trackers, a row stuck at the wrong angle can underperform for months. Inverters tripping off and reconnecting when grid voltage fluctuates also cost generation, yet the events are rarely logged.

For operators with several sites the picture is even more fragmented. Plants built in different years with different inverter brands are each watched in a separate portal, and nobody can compare them on the same basis. This fragmentation of a multi-site solar portfolio is the classic [remote monitoring](https://digitalbridge.com.tr/en/blog/remote-monitoring-iot-platform.html) problem, applied to energy assets.

## What do you lose without solar plant monitoring?

Solar is no longer a marginal source in Türkiye. According to [Türkiye's Ministry of Energy and Natural Resources' electricity page](https://enerji.gov.tr/bilgi-merkezi-enerji-elektrik), installed capacity reached 126,944 MW at the end of August 2026, 22% of it solar, and 41,749 of the country's 43,844 power plants are solar. The same source shows solar supplied 10.5% of Türkiye's electricity generation in 2025.

> Global solar PV additions exceeded 600 GW for the first time in 2025, lifting cumulative capacity to around 2,800 GW; solar made up more than three-quarters of new renewable capacity. ([IEA — Global Energy Review 2026, Solar PV and wind](https://www.iea.org/reports/global-energy-review-2026/technology-solar-pv-and-wind))

The Ministry's count includes unlicensed plants, and among them are many dispersed installations such as factory rooftops, agricultural irrigation systems and small ground-mounted arrays. Under Türkiye's unlicensed generation rules, self-consumption plants offset generation against consumption through the meter, so every day a plant underperforms shows up as extra energy bought from the grid. The investment case, meanwhile, assumes the plant really delivers the yield it was designed for.

Treating a factory rooftop plant as part of an [Industry 4.0 roadmap for SMEs](https://digitalbridge.com.tr/en/blog/industry-4-0-roadmap-smes.html), rather than as a separate island, makes the monitoring investment work harder. If the rooftop plant sits in an organised industrial zone, read its output alongside the zone's meter and your own measurements as described in [energy monitoring for factories in industrial zones](https://digitalbridge.com.tr/en/blog/industrial-zone-factory-energy-monitoring.html).

Without solar plant monitoring, the design-yield assumption is tested only at year end. A string offline for weeks, soiling that outpaces the cleaning plan or an inverter that trips repeatedly has already become a permanent loss by the time anyone notices.

Self-consumption plants have another side effect: as active energy drawn from the grid falls, the ratio of reactive to active energy can rise and bring the site closer to reactive penalty limits. That is why power factor belongs in the meter layer of monitoring; our article on the [reactive power penalty](https://digitalbridge.com.tr/en/blog/reactive-power-penalty.html) explains the rules.

## What should a solar power plant monitoring system measure?

A good solar power plant monitoring system puts "how much should we have produced?" next to "how much did we produce?". The table below summarises the measurement layers and the problems each one catches:

| Layer | Data collected | Problems it catches |
|---|---|---|
| Weather | Plane-of-array irradiance (pyranometer or reference cell), module and ambient temperature, wind | Calculating expected yield; separating weather dips from faults |
| String | String currents and voltages | Blown fuses, connector faults, shading, module defects |
| Inverter | AC/DC power, efficiency, alarms and fault codes, temperature | Inverter failure, overheating, frequent tripping |
| Meter and grid | Generated and exported energy, voltage, frequency, power factor | Grid-side outages, reactive energy balance |
| Site security | Cameras, door and cabinet contacts | Theft, intrusion, tampering with cabinets |

Collecting measurements continuously and with a common timestamp matters as much as measuring the right things. Data gaps are one of the most common reasons performance calculations mislead.

### What is performance ratio (PR), and why is it the most useful indicator?

Performance ratio (PR) compares the plant's actual output with the energy it could theoretically have produced from the irradiance it received over the same period. The International Electrotechnical Commission's (IEC) IEC 61724 family of standards sets out the framework for the calculation and the measurement set-up. PR is valuable because it is a health check that accounts for irradiance: on a cloudy day output falls, but if PR holds steady the plant is healthy, and if PR drops something on site needs attention.

Module efficiency does fall as temperature rises, however, so PR naturally dips a little in summer; a temperature-corrected PR, or comparing like seasons, gives a truer picture.

Breaking PR down to inverter and string level shows where the problem is. When plant-level PR slips slightly, only the lower-level breakdown can tell soiling apart from a fault on a single inverter. Combined with [electricity load forecasting](https://digitalbridge.com.tr/en/blog/electricity-load-forecasting.html), the expected-yield model also feeds self-consumption planning.

## How do you set up solar power plant monitoring? Seven steps

1. **Build an inventory.** For each site, list inverter makes and models, string counts, meter types, existing communications and the portals in use.
2. **Define the measurement set-up.** Decide where irradiance and temperature sensors go, whether string-level measurement is needed and what the logging interval should be, based on site size.
3. **Collect data independently of the manufacturer.** Read inverters directly over open protocols such as [Modbus](https://digitalbridge.com.tr/en/glossary.html#modbus) TCP and bring different brands into one data model. A set-up tied only to the maker's cloud resets your monitoring whenever the brand changes.
4. **Make communications robust.** For remote sites, weigh cellular against low-power wireless options using our [LoRa vs NB-IoT vs cellular comparison](https://digitalbridge.com.tr/en/blog/lora-vs-nb-iot-vs-cellular.html), and make sure data is buffered on site and sent later if the link drops. For outdoor enclosures, do not overlook the right [IP65 or IP67 rating](https://digitalbridge.com.tr/en/blog/ip-rating-explained.html).
5. **Build the expected-yield model.** Calculate expected output per inverter and string from irradiance and temperature, and report PR daily.
6. **Prioritise alarms.** Not every deviation is equally urgent. Keep a complete inverter stop and a small dip on one string in separate classes, and route alarms to the right person and into your [field service management](https://digitalbridge.com.tr/en/blog/field-service-management-guide.html) flow.
7. **Plan maintenance from the data.** Schedule cleaning by soiling loss rather than the calendar, and inverter servicing by temperature and fault trends. Our [predictive maintenance guide](https://digitalbridge.com.tr/en/blog/predictive-maintenance-guide.html) covers the wider approach.

### Security and multi-site management

Every remotely accessible inverter, data logger and [SCADA](https://digitalbridge.com.tr/en/glossary.html#scada) (Supervisory Control and Data Acquisition) server is also a cyber security exposure. Default passwords, management interfaces open directly to the internet and shared accounts are common weaknesses on energy sites; the countermeasures are covered in our article on [OT security and SCADA](https://digitalbridge.com.tr/en/blog/ot-security-scada.html).

In a multi-site solar portfolio, each site manager should see only their own plant while head office compares all of them on the same indicators. Role-based access, an audit trail showing who changed settings where, and a second approval for remote commands are hard to add later, so build them in from the start.

Scattered solar plants are also changing how distribution networks work. We cover metering, monitoring and field management on the grid side in our [energy utility digital transformation guide](https://digitalbridge.com.tr/en/blog/energy-utility-digital-transformation.html).

## How we build solar power plant monitoring at Digital Bridge

We do not sell off-the-shelf packages. We first review your sites and existing infrastructure, then provide a written proposal setting out scope, phases and cost, and technical feasibility for hardware projects is free of charge. Within our [energy and utilities solutions](https://digitalbridge.com.tr/en/industry-solutions/energy-utilities.html), the approach is:

- **Discovery and needs analysis.** We document the inverter, meter and communications inventory of your plants and agree which data sits where today and who makes which decisions.
- **Pilot on one site.** On your largest or most troublesome plant we bring inverter, irradiance and meter data onto one screen and switch on the PR and expected-yield comparison. Once validated, further sites join the same structure.
- **SCADA and remote monitoring.** For large sites we develop custom [SCADA and HMI](https://digitalbridge.com.tr/en/industry-40/scada-hmi.html); the source code belongs to you and there is no additional licence fee. For dispersed rooftop plants we bring every site into a single panel through our [remote monitoring platform](https://digitalbridge.com.tr/en/industry-40/remote-monitoring-saas.html).
- **Analytics and field data.** We flag deviations in string and inverter behaviour with [anomaly detection](https://digitalbridge.com.tr/en/technology-hardware/anomaly-detection.html) models and analyse drone imagery of large ground-mounted plants through [drone data processing](https://digitalbridge.com.tr/en/data-analytics/drone-data-processing.html).
- **Meter and grid data.** We bring generation, export and power factor data onto the same screen through [automatic meter reading (OSOS)](https://digitalbridge.com.tr/en/industrial-products/osos-meter-reading.html), so lost generation and reactive energy balance are tracked together.

Our article on [drone NDVI analysis](https://digitalbridge.com.tr/en/blog/drone-ndvi-analysis.html) shows, through an agricultural example, how drone imagery becomes meaningful data layers; the same processing logic applies on a solar site.

If you want the fundamentals first, our guide [what is SCADA](https://digitalbridge.com.tr/en/blog/what-is-scada.html) is a good place to start. To decide between an off-the-shelf product and a bespoke build, see our [commercial vs custom SCADA](https://digitalbridge.com.tr/en/blog/commercial-vs-custom-scada.html) comparison.

## Next step

One table is enough to begin: list your sites, the inverter brand at each, which portal you use to watch it today and the longest generation loss you noticed in the past year. Bring that table to us through our [contact page](https://digitalbridge.com.tr/en/contact.html), and we will choose the pilot site and measurement set-up together. For more guides on energy and site monitoring, visit our [Industry 4.0 topic page](https://digitalbridge.com.tr/en/blog/topic/endustri-40.html).

## Frequently Asked Questions

### Isn't the inverter manufacturer's portal enough?

For a small single-brand plant, the manufacturer's portal may cover the basics. But it usually shows only its own brand's data, does not calculate expected yield from irradiance and cannot compare different sites on the same basis. With more than one brand or site, collecting data independently of the manufacturer and tracking performance ratio reveals losses much earlier.

### Do we need an irradiance sensor for solar monitoring?

You need to know the irradiance on site to calculate expected yield. Satellite-based irradiance data can be used without a sensor, but it does not reflect local cloud cover or soiling with the same precision. On medium and large plants, plane-of-array irradiance and module temperature sensors are regarded as essential for a reliable performance ratio calculation.

### What should we do if performance ratio drops?

First check whether the drop affects the whole plant or a specific inverter or string. A gradual, plant-wide decline usually points to soiling, while a sudden local drop suggests a fuse, connector, inverter or shading problem. The data tells you which equipment and which team to send, so unnecessary site visits also fall.

### Do rooftop solar plants need monitoring too?

Yes, particularly self-consumption rooftops on factories. Every day the plant underperforms appears as extra energy bought from the grid, and the payback calculation suffers. On smaller rooftop plants, a simple set-up based on inverter and meter data shows most losses without the need for a full SCADA system.

### What does solar power plant monitoring cost?

The cost depends mainly on the number of sites, the make and number of inverters, whether string-level measurement is needed, irradiance and temperature sensor requirements and the communications available on site. If existing inverters already share data over open protocols, less extra hardware is required. The soundest approach is to start with a pilot on one site and settle scope and cost from its results.

### Can inverters from different brands be monitored in one system?

Yes. Most inverters share data over open protocols such as Modbus, and data from different brands is brought into a common model. Plants built over the years with different brands can then be compared on one screen using the same indicators. Older devices without open protocol support can be read through an additional data logger or external measurement.