It costs a heck of a lot to put up a 1 MW of solar PV power plant - a minimum of $3 million per MW. A solar PV power plant produces an output of about 1.5 million kWh per year. But all these units might not be realized if you do not have proper monitoring systems in place.

As this Blog says, "The simplest monitoring involves simply checking the inverter, and this is done by reading values on the display, which is typically the LCD part of almost each grid-connected inverter.

The variables which can be monitored include PV array power, AC (grid) power, PV array current etc. For sophisticated monitoring and control purposes, environmental data, such as module temperature, ambient temperature, solar radiation, wind speed etc., can also be logged in data loggers, stored, and later analyzed.

Remote control and monitoring can be performed by various remote connections, such as ISDN, GSM, analog modem etc. More important inverter or grid related parameters can hence be made available on-line"

Cutting a long story short, monitoring systems can ensure that a solar PV power plant is able to have minimal breakdowns, thus resulting in the production of the expected output. While a monitoring system is unlikely to increase the output of a solar farm, the absence of such a system is likely to significantly decrease the output from the stated output of the farm.

Here is a link that might be useful: Monitoring Systems for Solar PV