How to Choose the Right Capacity for Your Rooftop Solar System in India (2025 Guide)

Switching to rooftop solar is a smart decision — it saves money, reduces your carbon footprint, and gives you energy independence.
But here’s the tricky part: how do you know what capacity of solar system you actually need?

If you choose a system that’s too small, it won’t cover your needs. If it’s too big, you’ll end up spending more than necessary.
Let’s break it down step-by-step in simple terms.rooftop solar capacity

---

1. Understand What “Capacity” Means

The capacity of a solar system is measured in kilowatts (kW).
Example: A 5 kW solar system can generate roughly 20–25 units (kWh) of electricity per day in good sunlight conditions.

---

2. Check Your Monthly Electricity Usage

The first step is to know how much electricity you actually use.

• Look at your last 12 months’ electricity bills.
• Note the average monthly units (kWh).
• Example: If you use 600 units per month, that’s about 20 units per day.

---

3. Match Your Consumption with Solar Output

In India, 1 kW of rooftop solar generates 4–5 units per day on average.

So, the formula is:

Required Solar Capacity (kW) = Your Daily Consumption (units) ÷ 4–5

Example:
Daily consumption = 20 units
20 ÷ 4 = 5 kW system needed

---

4. Consider Your Roof Space

Each 1 kW solar system needs about 100 sq. ft. of shadow-free roof space.

Solar Capacity	Roof Space Needed
1 kW	~100 sq. ft.
3 kW	~300 sq. ft.
5 kW	~500 sq. ft.
10 kW	~1000 sq. ft.

Tip: Ensure there are no tall trees or buildings casting shadows on your panels.

---

5. Decide Between Partial or Full Load Coverage

• Full load coverage: Your system meets all your needs year-round.
• Partial coverage: The system covers part of your needs, and the rest comes from the grid.

If your budget is limited, you can start small and expand later.

---

6. Factor in Net Metering

With net metering, extra electricity you produce is sent to the grid and adjusted in your bill.
If your state offers this, it’s worth installing a slightly bigger system to maximize savings.

---

7. Plan for the Future

Think about upcoming changes:

• Adding new appliances like ACs or EV chargers?
• Planning to shift to electric cooking?

If yes, choose a slightly higher capacity to cover future needs.

---

8. Consult a Solar Expert

While calculations help, a professional site visit ensures accuracy. Experts measure:

• Roof size
• Sunlight availability
• Wiring setup
• Inverter type suitability

---

Quick Example Calculation

Let’s say:

• Monthly usage = 900 units
• Daily usage = 30 units
• In India, 1 kW solar = ~4.5 units/day

So:

30 ÷ 4.5 = 6.6 kW

You’d need around 6.5–7 kW capacity.

---

Key Takeaways

• Check your daily average consumption.
• Match it with solar output in your area.
• Ensure you have enough shadow-free roof space.
• Plan for future expansion.
• Always confirm with a professional.

Enquiry Form