Sizing Guide: The Right Battery for a 3kW PM Surya Ghar Setup

The PM Surya Ghar scheme is pushing a lot of Indian households toward rooftop solar. The 3kW setup is the obvious favorite right now because it gets you the maximum ₹78,000 subsidy.

But installing the panels is only the first step. If you do not have a properly sized battery, you end up exporting your excess daytime power to the grid for pennies and buying it back at peak rates when the sun goes down. That entirely defeats the purpose of "Muft Bijli".

You need the right battery. Let's look at exactly how to size a LiFePO4 battery for a typical 3kW home setup.

Step 1: Know your solar output

A 3kW solar panel setup in India generates an average of 12 to 15 units (kWh) of electricity per day. This depends heavily on the season and your city.

Most of this power is generated between 10:00 AM and 3:00 PM. That is an average daily output of about 13.5 units.

During the day, this electricity runs your ceiling fans and refrigerator directly. But in most households, the family is at work or school during these hours. Nearly half of your generated power has nowhere to go. You need to store it.

Step 2: Add up your nighttime power usage

To size your battery correctly, you have to estimate your power consumption from 6:00 PM to 6:00 AM.

Here is what a typical middle-class Indian home load looks like at night:

• 1 Inverter AC (1.5 Ton, running at 50% load): 800W × 6 hours = 4.8 kWh
• 1 Refrigerator (Double Door): 200W × 12 hours = 2.4 kWh
• 3 Ceiling Fans: 210W (70W each) × 10 hours = 2.1 kWh
• 4 LED Tube Lights: 80W (20W each) × 6 hours = 0.48 kWh
• 1 TV (55 inch LED): 100W × 4 hours = 0.4 kWh
• Phone chargers and a WiFi router: 50W × 12 hours = 0.6 kWh

That adds up to roughly 10.8 units of electricity needed just for the night. Let's round it to 11 units.

Step 3: Pick the capacity

You need 11 kWh of storage. Batteries are rated in Voltage (V) and Ampere-hours (Ah). You calculate total energy by multiplying the two: Energy (Wh) = Voltage (V) × Ampere-hours (Ah).

For a 3kW solar system, a 48V battery setup is the standard recommendation.

11,000 Wh ÷ 48V = 229 Ah.

A 48V 200Ah or 250Ah battery bank is exactly what you need.

Why the battery chemistry matters

This is where people make expensive mistakes.

If you buy lead-acid batteries, you can only safely discharge them to 50% of their total capacity. Discharging them further destroys their lifespan. To actually get 11 kWh of usable power at night, you would need a massive 22 kWh lead-acid battery bank. That means buying and finding space for eight heavy 12V 200Ah batteries.

LiFePO4 batteries are different. A good LiFePO4 battery safely discharges to 95% or even 100% of its capacity. A single 48V 200Ah LiFePO4 battery provides 9.6 kWh of usable energy. It takes up a fraction of the space and lasts four times longer than a lead-acid bank.

Step 4: Check your inverter

A 3kW solar setup requires a 3kVA to 5kVA hybrid solar inverter. If you decide to go with a 48V LiFePO4 battery, you must buy a 48V inverter. They have to match.

For a standard 3kW PM Surya Ghar installation, we recommend the Mecanum 48V 200Ah LiFePO4 Wall-Mounted Powerwall.

It provides 9.6 kWh of usable energy, which comfortably absorbs your excess daytime solar and runs a 1.5-ton AC all night. It mounts flat on your wall, saving floor space. There are no acid fumes and no top-ups required. The built-in Battery Management System integrates safely with modern hybrid inverters. It is designed to handle daily deep cycling for over a decade.

Conclusion

The PM Surya Ghar scheme is a brilliant opportunity to cut your electricity bills. But tying a brand new solar array to outdated lead-acid technology is a bad move. You will end up paying for replacements every three years.

Size your system right. A 48V 200Ah LiFePO4 battery ensures that the free electricity you generate during the day actually keeps your home cool all night.

Need help calculating your specific load? Try our Smart Power Planner or contact our engineering team.