Step 1: Find your units, not your rupees
Your bill shows units consumed (kWh) for the billing month. Rupee amounts include fixed charges, duty and slab rates, so they are a poor guide. Look at 6–12 months if you can — summer bills with ACs are much higher than winter ones. See how to read your MP electricity bill.
Step 2: Divide by what 1 kW produces in Indore
A south-facing array in Indore produces about 122 units per kW per month on average across the year.
System size (kW) ≈ average monthly units ÷ 122
Quick sizing table
| Average monthly units | Suggested size | Roof needed | Panels (545 W) |
|---|---|---|---|
| 100–150 | 1 kW | ~90 sq ft | 2 |
| 150–250 | 2 kW | ~180 sq ft | 4 |
| 250–400 | 3 kW | ~270 sq ft | 6 |
| 400–520 | 4 kW | ~360 sq ft | 8 |
| 520–700 | 5 kW | ~450 sq ft | 10 |
| 700–850 | 6 kW | ~540 sq ft | 11 |
| 850–1,100 | 8 kW | ~720 sq ft | 15 |
| 1,100–1,400 | 10 kW | ~900 sq ft | 19 |
Worked example: a 3BHK in Indore
A family averages 380 units a month (higher in May, lower in January).
- 380 ÷ 122 = 3.1 kW → 3 kW
- Generation: about 4,377 units a year
- Estimated savings: about ₹2,736 a month at ₹7.5/unit
- Price after ₹78,000 subsidy: around ₹1.11 lakh
- Payback: about 3.3 years
Worked example: a large home
A duplex averages 620 units a month with three ACs.
- 620 ÷ 122 = 5.1 kW → 5 kW
- Savings: about ₹4,559 a month
- 25-year savings: about ₹18.65 lakh
Should you size bigger than your use?
Usually not. Under net metering, surplus units beyond what you consume over the settlement period are credited at a much lower rate than you pay to buy power. Sizing to 90–100% of your annual consumption gives the best return. The exception is when you are about to add load — an EV, another AC, a home office — in which case size for next year's bill.
Things that can limit your size
- Roof area after removing tanks, stair headroom and shaded zones.
- Sanctioned load: net-metered capacity is generally linked to it; a load enhancement can be applied for.
- Phase: larger systems may need a three-phase connection.
- Budget: the subsidy caps at 3 kW for homes, so the step from 3 to 4 kW is paid fully by you — but still pays back.
The fastest way to get this right is to upload your bill to our calculator, which reads the units and does the maths on your device.