Start with units, not kilowatts
Your electricity bill states your consumption in units — kilowatt-hours. That number, totalled across a year, is what a solar system has to match. Kilowatts describe the size of the equipment; units describe the job it has to do. Sizing from kilowatts is guessing.
Pull twelve months of bills, not one. Gujarat households swing hard between a March bill and a May bill, and a system sized on a mild month will disappoint every summer.
What a kilowatt generates here
Gujarat has genuinely good irradiance. Averaged across the year, a well-sited and reasonably clean kilowatt of rooftop solar generates roughly four to four and a half units a day. In practice, a 3 kW residential system in Gujarat is generally cited as producing around 12 to 15 units a day, or somewhere in the region of 4,200 to 4,350 units a year.
| System | Typical daily generation | Roughly per year |
|---|---|---|
| 2 kW | 8 – 10 units | ~2,900 units |
| 3 kW | 12 – 15 units | ~4,200 – 4,350 units |
| 5 kW | 20 – 25 units | ~7,000 units |
Treat those as planning figures rather than promises. Real output depends on shading, orientation, module quality, how often the array is cleaned, and how hot the roof gets — panels lose efficiency as temperature rises, which matters in a Gujarat May.
Two hard limits
Your sanctioned load
Under Gujarat's net metering rules, the system you connect cannot exceed your sanctioned load. If your home is sanctioned for 3 kW, a 6 kW array is not simply a bigger purchase — it is an application to raise your sanctioned load first. That is a solvable problem, but it is a step, and it has to happen before commissioning, not after.
Your shadow-free roof
As a planning rule of thumb, allow somewhere around 90 to 110 square feet of genuinely shadow-free roof per kilowatt. What kills residential systems is not total area but obstruction: a water tank, a lift room, a parapet, a neighbour's tower going up next year. Shading costs more output than orientation does — a slightly off-south array in clear sun beats a perfectly south-facing one under a tree.
Before you size anything
- Twelve months of bills, not one
- Your sanctioned load, from the bill
- Usable shadow-free roof area, measured
- Whether anything is likely to shade the roof in the next few years
Why bigger is not automatically better
In Gujarat, surplus units you export are compensated at a regulated rate that sits well below what you pay to import. That asymmetry is the whole argument for sizing to consumption rather than to roof area: a unit you use yourself is worth what you would have paid for it, while a unit you export is worth the export rate. Deliberately oversizing to sell power back is a much weaker deal than it sounds.
Add the subsidy cap at 3 kW, and you can see why a large share of Gujarat homes land on a 3 kW system. That is not a coincidence, and it is not always right either — a household running two air conditioners through summer may be leaving real savings on the table at 3 kW.
The figures here are typical ranges for planning, not a performance guarantee. A site assessment is what turns them into numbers for your specific roof.