Panels differ less than customers imagine. Inverters differ more than they imagine. Choosing the wrong category is the single most consequential decision in a residential rooftop design, because it determines what happens on the evening the grid goes down — which is the moment the customer forms their opinion of the whole system.
On-grid: the default, and usually correct
A grid-tied string inverter converts DC to AC and exports surplus to KSEB. It is the cheapest route to the lowest bill, and for most net-metered Kerala homes it is the right answer.
The point customers consistently misunderstand: an on-grid system shuts down during a power cut. This is a mandatory safety behaviour called anti-islanding — it prevents your array from energising a line that a lineman believes is dead. It is not a fault, and it is not something a better inverter avoids.
Specify on-grid when the grid is reasonably reliable, the customer's priority is bill reduction, and backup is not part of the brief.
Hybrid: solar plus storage in one unit
A hybrid inverter manages panels, battery and grid together, and can carry selected loads through an outage. In Kerala — where monsoon outages are a routine fact rather than an exception — this is a genuinely valuable proposition rather than an upsell.
Specify hybrid when any of the following is true:
- The customer experiences frequent or extended outages, particularly in monsoon months.
- There is equipment that genuinely must stay running — a medical device, a home office, refrigeration for a business.
- The household consumes most of its power in the evening, so storing daytime generation is worth more than exporting it.
- The site is above 10 kW, where Kerala's storage requirement applies in any case.
Be honest about the arithmetic. Batteries add substantial cost and have their own replacement cycle. A hybrid system sold purely on payback rarely justifies itself against an on-grid system; sold on resilience, it justifies itself easily. Sell it as what it is.
Off-grid: a narrow, real use case
Off-grid systems run independently of KSEB entirely, with a battery bank carrying the full load. In Kerala this is a minority application — remote sites, plantation or hill properties with poor or absent supply, and installations where a grid connection is impractical rather than merely inconvenient.
Off-grid design is a different discipline: you are sizing for worst-case autonomy across consecutive monsoon days with minimal generation, not for annual average output. Undersize the bank and the customer runs out of power in exactly the week they most need it.
Sizing details that cause callbacks
- Phase. Match the inverter to the service connection. Single-phase is normally capped around 3 kW in Kerala; above that you need three-phase, and the customer may need a connection upgrade.
- MPPT window. Check your intended string voltage against the actual MPPT range across the temperature extremes the site will see, not just at 25 °C.
- Surge capacity. On hybrid installations, confirm the inverter's surge rating handles motor starting loads — pumps and compressors are what trip an undersized unit.
- Ingress and siting. Kerala's humidity and salt air near the coast are hard on electronics. Mount to specification, in shade, with genuine ventilation clearance.
Service is part of the specification
An inverter is the component most likely to need attention across the system's life. When comparing options, the question is not only what the unit does but what happens when it stops doing it — how claims are raised, how long a replacement takes, and whether the unit has to leave the state.
RGS Associates runs a dedicated Deye Service Centre in Kozhikode, which means warranty attention for Deye units is handled within Kerala rather than through a chain that ends somewhere else. For an installer carrying the customer relationship, that difference in turnaround is the difference between a manageable service call and a month of angry phone calls.
Common questions
Does rooftop solar work during a power cut?
A standard on-grid system shuts down during an outage. This is a mandatory safety function called anti-islanding, which protects line workers. Only a hybrid or off-grid system with battery storage can supply power during a grid failure.
Is a hybrid inverter worth the extra cost in Kerala?
It depends on the priority. Judged purely on payback, a hybrid rarely beats a plain on-grid system. Judged on resilience during monsoon outages, or where the household consumes mostly in the evening, it is often worth it.
What size inverter do I need for a 5 kW solar system?
Broadly a 5 kW inverter, sized with a sensible DC-to-AC ratio rather than an exact match. In Kerala a 5 kW system will generally require a three-phase inverter and a three-phase service connection.