Residential
Rooftop solar for your home.
An on-grid system on a Kerala house does one thing extremely well: it cuts the KSEB bill, permanently, using a roof that is otherwise just collecting heat. Here is how it is sized, what it costs, and what it will and will not do for you.
Sizing it from your bill.
The honest way to size a home system is from consumption, not from roof area or from what the neighbour installed. Take the monthly units on your KSEB bill and divide by about 122 — that is roughly the kilowatt rating needed to cover them, using a Kerala generation assumption of about 1,460 kWh per kW per year. A house consuming 400 units a month lands near 3.3 kW.
Most Kerala homes end up between 2 kW and 5 kW. Three kilowatts is the most common outcome, partly because it suits a typical household and partly because the central subsidy stops increasing above it.
Roof area is the second constraint, at roughly 100 sq ft of usable unshaded space per kW. Usable is the operative word: a large roof interrupted by a water tank, a stair head and a coconut palm's afternoon shadow can offer less working area than a smaller clear one.
The subsidy is genuinely large.
PM Surya Ghar pays ₹30,000 for each of the first two kilowatts and ₹18,000 for the third, capping at ₹78,000. On our own price for a 3 kW system, ₹2,15,000 installed, that is a bit over a third of it back.
It is residential-only and it is paid to you, into the bank account on your own application, after the system is commissioned and the net meter is live. Delta never receives it on your behalf. We prepare the KSEB side and sit with you through the national portal registration, which has to be done against your own consumer number.
What it does through a Kerala year.
Panels generate from daylight, not from direct sun, so an overcast monsoon day still produces — well below a clear February day, but not nothing. Systems are specified against annual generation precisely because Kerala's year is uneven, and the 1,460 kWh per kW figure already has the monsoon inside it.
Heat is the less obvious factor. Silicon loses output as it warms, so the hottest afternoons are not the most productive ones. It is one reason a panel's temperature coefficient is worth asking about in a climate like this.
One thing an on-grid system will not do is keep your lights on during a power cut. A grid-tied inverter disconnects the moment the grid drops, as a safety requirement. If outages are the problem you want solved, that is a hybrid system, not this one.
Your roof, and what we check.
Concrete, tiled and sheet roofs are all routine work with different mounting structures. What we are assessing on the site visit is usable unshaded area, the path of shadows through the day, the condition of the roof surface, and where the inverter and cable runs will sit.
Properly mounted, an array shades the roof beneath it and measurably reduces heat gain into the rooms below. Poorly mounted, it creates leak paths through the waterproofing. The difference is entirely in how the penetrations are made and sealed, which is why we would rather tell you a roof needs attention first than build on it.
Planning for what comes later.
If an electric vehicle or additional air conditioning is anywhere in your plans, say so before the system is designed. The constraint on expansion is usually the inverter's capacity and your sanctioned load rather than free roof space, and sizing the inverter with headroom now costs far less than replacing it later.
