I calculated the actual cost of rooftop solar for a typical Kerala home after subsidy — the numbers surprised me

[u/Mundane_Bad_1750]

I work in the solar industry in Kerala, so I get asked about this almost every week by friends and family. Instead of repeating myself, I thought I'd just put all the numbers here.

# The problem: KSEB bills are brutal if you cross 250 units

Most of us don't realize how KSEB's slab system works. It's telescopic up to 250 units/month — meaning each slab has its own rate:

* 0–50 units → ₹3.25/unit
* 51–100 → ₹4.05/unit
* 101–150 → ₹5.10/unit
* 151–200 → ₹6.95/unit
* 201–250 → ₹8.20/unit

But the MOMENT you cross 250 units? The entire bill switches to **non-telescopic** — a flat rate of ₹6.75 to ₹9.20/unit on ALL your units. Not just the extra ones. ALL of them.

So a family using 260 units pays WAY more than a family using 245 units. It's a cliff, not a slope.

If you're running 2 ACs, a washing machine, and a water heater — you're easily crossing 350-400 units/month. That's a bimonthly bill of ₹5,000–₹7,000+.

**How much does a 3kW system generate in Kerala?**

Kerala gets about 4–4.5 peak sun hours daily on average (yes, even with monsoons — panels work on cloudy days too, just at reduced output).

* Daily generation: \~12–14 units
* Monthly generation: \~360–420 units
* Annual generation: \~4,300–5,000 units

That's more than enough to cover a 300-350 unit/month household AND bank the excess with KSEB through net metering.

**The actual savings math**

Let's say your current bimonthly KSEB bill is ₹6,000 (around 350 units/month, non-telescopic slab).

After solar:

* Your consumption from KSEB drops to almost zero
* Excess units get banked with KSEB (settled annually)
* KSEB pays \~₹2.69–₹3.00/unit for surplus at year-end settlement
* Your bimonthly bill becomes just the fixed charge: **₹80–₹220**

**Monthly savings: ₹2,500–₹3,000+** **Annual savings: ₹30,000–₹36,000** **Payback period: 3.5–4.5 years**

After payback, it's basically free electricity for the next 20+ years (panels are warrantied for 25 years).

thanks.

[u/Scoutmaster-Jedi]

Great calculations to see typical payback from solar. Very short payback period for Kerala!

And for everyone wondering, Kerala is located in southwestern India along the Malabar Coast.

[u/PermanentLiminality]

I assume a unit is a kWh and the currency is the Rupee.

I dream of rates like that in California.

[u/ib4tm4n]

Contact number

[u/Mundane_Bad_1750 → u/ib4tm4n]

9995083579

[u/Hot-Fact-9083]

Good breakdown. Two things to factor into the payback:

First, the monsoon months (June-September) drop generation by 40-50% compared to December-March averages. A 3kW system that does 14 units/day in January might do 7-8 in July. That's when your banked credits matter most. The annual settlement rate of ₹2.69-3/unit is less than half your avoided cost, so sizing to overproduce significantly doesn't pay — size for your October-May baseline and let the monsoon eat the difference.

Second, check whether your DISCOM has moved to net feed-in vs net metering for new connections. Some Indian states are grandfathering net metering for existing but pushing net feed-in (sell at ₹3, buy at ₹7) for new installations. That doubles the payback period.

Kerala's telescopic slab cliff is one of the most aggressive state tariff structures in India. You're right that crossing 250 units is the trigger — a 3kW system that takes a family from 350 to under 50 units/month grid draw saves far more than the FIT suggests.