Free Solar Analytics Tools for Plant Performance

CUF measures how much energy a solar plant actually generates relative to its rated capacity over a given period, so it is strongly influenced by the solar resource available at the site. PR compares actual generation with the expected generation based on measured plane-of-array irradiance and the installed PV capacity, making it more suitable for assessing plant performance under the solar resource actually received.

A good Performance Ratio (PR) depends on the plant design, location, operating conditions, and calculation methodology. As a general indication, a PR above 80% often indicates strong performance with losses within expected limits. A PR between 70% and 80% can be normal for many commercial solar plants, depending on site conditions and system losses. A PR below 70% may indicate significant performance losses and should trigger a structured loss analysis to identify the cause.

Performance Ratio (PR) naturally drops in summer because module temperatures rise significantly above the 25°C Standard Test Conditions (STC) reference. Most crystalline silicon modules lose about 0.35–0.45% efficiency per °C above 25°C, so a cell temperature of 55°C can reduce output by 10–13%. This is expected thermal behavior — not a fault. Use Temperature Corrected PR for a fairer comparison across seasons.

Always use POA (Plane of Array) insolation for accurate PR calculation. GHI (Global Horizontal Irradiance) measures sunlight on a flat horizontal surface, but your PV modules are tilted. POA represents the actual irradiance hitting the module surface and is the standard required by IEC 61724-1. Using GHI instead of POA can skew your PR by 5–15% depending on tilt and latitude.

Soiling analysis helps determine when solar panels should be cleaned by measuring how much energy production is being lost due to dust and dirt. Instead of following a fixed cleaning schedule, operators can use the measured soiling loss to decide when cleaning is worth the cost. In utility-scale plants, around 3–5% soiling loss is often used as a practical cleaning trigger, although the appropriate threshold depends on local conditions, cleaning costs, and electricity revenue.

NMGG (Net Minimum Guaranteed Generation) is the minimum annual AC energy output a plant is contractually obligated to deliver under its PPA, typically measured at the grid interconnection point after auxiliary consumption. Falling below this threshold triggers financial penalties or deemed generation adjustments depending on the contract structure. Monthly NMGG targets are usually derived by distributing the annual figure proportionally across months based on expected POA insolation — so months with higher irradiance carry higher targets, reflecting the plant's actual generation potential through the year.

Our calculators implement formulas directly from IEC 61724-1:2021 and MNRE guidelines — the same standards used in commercial PV monitoring software. Computational accuracy is exact (limited only by your input precision). Real-world accuracy depends on your data quality: calibrated sensors, proper POA measurement, and clean inverter readings. Core formulas and references are documented on our GitHub repository, with more being added over time.