The IEC 61853-1 standard published in January 2011 specifies a performance rating matrix at various temperatures and irradiance levels of a PV module. In the conventional method, this target matrix is generated using all the data points of several measured I-V curves and the translation procedures defined in IEC 60891 standard. In the proposed method, the target matrix is generated using only three commonly field measured parameters: module temperature, incident irradiance and MPPT (maximum power point). The MPPT could be either (or both) dc values of the array before inverter or ac values of the system after inverter. The proposed method can also be used as an online system level diagnostic tool to monitor the health of dc array (and/or ac system) over time (year over year) for performance degradation or soiling effect at any specific set of temperature-irradiance conditions. The primary objectives of the paper include: 1) Automatically generating P max matrix as per IEC 61853-1 in about 30 seconds using an interpolation and extrapolation of 6-minute MPPT data monitored and collected over 3 days on a fixed tilt module; 2) Checking the power linearity with irradiance and temperature of the test modules as per IEC 60904-10; 3) Calculating the RMSE (root mean square error) values; and 4) Validation of the program. The monitored three-column data points (temperature, irradiance and P mppt) are simply loaded on a preprogrammed Excel spreadsheet. With a click of a button provided in the spreadsheet, the IEC 61853-1 required P mppt matrix is displayed on the screen in about thirty seconds. In addition, along with the RMSE value, the program generates several plots including: 1) Irradiance versus P mppt; 2) Module temperature versus P mppt; and 3) Accuracy check with "Actual P mppt versus Calculated P mppt".