What is plant load factor?

The performance of a power plant can be expressed through some common performance factors as: energy efficiency, thermal efficiency, capacity factor, load factor, economic efficiency and operational efficiency. The net capacity factor of a power plant is the ratio of its actual output over a period of time, to its potential output if it were possible for it to operate at full nameplate capacity indefinitely.

To calculate the capacity factor, take the total amount of energy the plant produced during a period of time and divide by the amount of energy the plant would have produced at full capacity. Capacity factors vary greatly depending on the type of fuel that is used and the design of the plant. The capacity factor should not be confused with the availability factor, capacity credit (firm capacity) or with efficiency.

Though India is aiming for 100 GW solar power, the PLF of a solar plant is typically 20-25 per cent only. In other words, the actual power supplied by a solar plant would be one fourth of its installed capacity. It is said that NTPC’s PLF was 81.5% in 2013-14. This means to set up a solar plant would cost four times a thermal power plant. However, the operational cost of a solar plant is nearly zero and initial high investments would be offset over a period of time.

Improving the PLF of a power plant would reduce the cost of unit of power supply to consumers. If the PLF is affected by non-availability of fuel, maintenance shut-down, unplanned break down and no offtake (as consumption pattern fluctuates lower in nights), the generation has to be adjusted.

A power (electricity) storage is not feasible. A generation of power is controlled to match the offtake. In India, the plant load factor has been declining in the past few years, going down to a low of 65 per cent in 2013-14, as compared to 79 per cent in 2007-08.