Three Compliant Battery Sizes for a 1 MW Maharashtra Plant, and Why They Differ

Most quotes for a 1 MW solar plant in Maharashtra show one battery size: 500 kW × 2 h. That is the base rule under the state's storage mandate, but it is not the only compliant answer. There are at least three, and they don't cost the same.

Three compliant configurations

• 500 kW × 2 h: the base rule, 1 MWh of storage at half the plant's capacity
• 250 kW × 4 h: the same 1 MWh of energy, at half the power rating
• 500 kW × 4 h: the configuration that can unlock the 10-year duty holiday for captive projects

Why the choice matters

All three satisfy the mandate, but they are different machines. The first two store the same 1 MWh, one at 500 kW and the other at half that power rating. The third doubles the energy to 2 MWh at 500 kW, and for captive projects it is the configuration that can unlock a 10-year duty holiday. Because they don't cost the same, they don't pay back the same either: Ingro modelled all three for one Pune plant on Ingro Sims, and payback varied across the three.

A quote that shows only the base rule has answered the compliance question. It has not necessarily answered the commercial one.

The question to put to your EPC

If your quote shows only 500 kW × 2 h, ask your EPC which configuration they quoted, and why. The cheapest compliant battery and the best-paying compliant battery are not necessarily the same one, and the answer depends on the plant's own load and whether the project is captive.