For a Kerala installer, net metering is the step where system design meets regulation. Size a system without checking the thresholds and you will discover them at inspection — which is the most expensive place to discover anything.
Capacity limits for domestic connections
Domestic rooftop systems generally run from 1 kW to 20 kW, subject to the consumer's sanctioned connected load and to feasibility at the local transformer. The connected-load constraint catches people out: a modest existing connection may not support the system a customer has budgeted for, regardless of available roof area.
Check the sanctioned load on the customer's bill during the first visit. It costs nothing and prevents designing a system the connection cannot legally carry.
The single-phase ceiling
This is the threshold that reshapes more quotations than any other. A single-phase inverter is normally capped around 3 kW. Above that, the installation needs a three-phase inverter — and therefore a three-phase service connection.
In practice this is why 3 kW is the workhorse size in Kerala residential solar. It sits exactly at the single-phase ceiling and exactly at the subsidy cap — the two constraints happen to align, which is convenient for everyone.
Storage requirements on larger systems
Kerala applies storage obligations to larger domestic installations, on a sliding basis:
| System size | Storage requirement |
|---|---|
| Up to 10 kW | No storage requirement |
| Above 10 kW up to 15 kW | 10% storage |
| Above 15 kW up to 20 kW | 20% storage |
This materially changes the economics of anything above 10 kW, and it should appear in the quotation from the outset. A customer who budgets for a 12 kW array and then meets a battery requirement will reasonably feel misled.
How surplus is settled
Exported surplus is banked and settled at a regulated rate, with existing prosumers and new prosumers on different tariffs, and a small monthly banking charge applied to banked units. Reported figures put existing prosumers around ₹3.08 per kWh and new prosumers around ₹2.79 per kWh, with a 2% monthly banking charge.
The wider design implication is stable even when the exact tariff moves: self-consumption is worth more than export. Since banked surplus settles below the retail tariff the customer pays, a system sized to cover daytime load earns more than one sized to push maximum units onto the grid. For households where nobody is home during the day, that argues for a smaller array or for storage.
Getting through approval without a second visit
- Confirm sanctioned load and phase before finalising system size.
- Match inverter phase to the service connection — this is the most common rework.
- Check that the meter position and available board space suit a net meter before installation day.
- Keep earthing and protection to specification; inspection failures cluster here.
- Hold the commissioning documentation together, since the subsidy claim depends on it.
Kerala's regulatory position for new applicants has been evolving, so the sensible discipline is to verify the live KSEB and KSERC position on capacity, settlement and storage before finalising any system that sits near a threshold.
Common questions
What is the maximum rooftop solar capacity for a domestic connection in Kerala?
Domestic net-metered systems generally run from 1 kW to 20 kW, subject to the consumer's sanctioned connected load and local feasibility.
Do I need a three-phase connection for a 5 kW solar system in Kerala?
Generally yes. Single-phase inverters are normally capped around 3 kW, so systems above that require a three-phase inverter and a corresponding three-phase service connection.
Is battery storage mandatory for rooftop solar in Kerala?
Not for systems up to 10 kW. Above 10 kW and up to 15 kW a 10% storage requirement applies, and above 15 kW up to 20 kW it rises to 20%.