Maharashtra's storage rule for commercial solar: a plain guide for sites

If your hospital, campus or commercial building in Maharashtra is planning new rooftop or captive solar above 100 kW, plan for a battery alongside it. Here is what is on the table, a worked sizing example, and the questions worth asking any supplier.

What is on the table

• Maharashtra's RE and Storage Policy, notified in March 2026, is reported to link storage to new solar above 100 kW: a battery of at least 50% of the solar capacity, for at least 2 hours, for applications from 1 April 2026.

• In September 2026, MERC published draft rooftop regulations that would require storage with new grid-interactive rooftop and behind-the-meter systems above 100 kW: 50% of capacity for 2 hours, or 25% for 4 hours.

• The draft also sets a minimum of 1 kWh of storage per kW of solar until 2030, rising to 2 kWh per kW after that.

• Systems of 100 kW or less, and systems already approved for grid connection, are reported to be outside the requirement.

The final notified text is what counts. Check it, and your DISCOM's procedure, before you sign a solar or battery order.

A worked example

A site adding 200 kW of rooftop solar would need a battery of at least 100 kW for 2 hours: 200 kWh of usable storage.

That battery need not sit idle. Sized and wired for it, the same battery can carry critical circuits through grid outages, so the diesel generator runs less.

Questions to ask any battery supplier

1. Is the quoted capacity usable kWh or nameplate kWh, and how much is guaranteed at the end of the term?

2. What does the warranty cover (years, cycles or energy delivered), and what voids it?

3. Which fire-safety standard is the system built to, and who signs off the installation?

4. Who maintains it, how fast do they respond, and is that written into the contract?

5. Can the battery also back up critical circuits, and how quickly does it switch over?

6. If you would rather not buy it outright, is a monthly plan available, and who owns the battery?

Where Vaultus fits

Vaultus works with battery makers, lenders and insurers so a site can take the battery on a monthly plan, maintained by its maker, with uptime written into the contract. Your battery, our problem.

Send three months of electricity bills and your solar plan to contact@vaultus.io and we will come back with a site estimate.

Sources: SolarQuarter on the MERC draft rooftop regulations (Sept 2026); Reslink on the Maharashtra storage requirement.