3 kW vs 5 kW rooftop solar — same subsidy ceiling, different bill fit

Size from units, not only rupees

Tariff slabs differ by DISCOM, so two homes with the same ₹ bill can have different unit counts. Rough India thumb-rules (conservative, weather-dependent):

• ~3 kW often offsets on the order of ~300–400 units/month in many metros (varies with monsoon, shade, orientation).
• ~5 kW aims closer to ~500–650+ units/month when the roof and sanctioned load allow.

Targeting 80–90% of annual units is usually safer than “zero bill forever” claims — fixed charges and export settlement rules still leave a residual bill.

When 3 kW is the rational default

• Consumption sits near or below what 3 kW can offset most months
• Roof area is tight (~250–300 sq ft shadow-free is a common planning band)
• You want maximum CFA per rupee of plant cost

When 5 kW can still win

• Sustained high AC / EV / multi-storey daytime load above 3 kW output
• Sanctioned load and DISCOM rules allow the larger plant
• You accept longer payback because the extra kW is unsubsidised

Oversizing so surplus banks at a low year-end rate can destroy returns — especially if you export what you never self-consume at high slab tariffs.

Next step

Run the Sealix home check from your bill, then read PM Surya Ghar and costs & savings. City context: Pune, Chennai, Bengaluru, Mumbai.

Check which size fits my bill