Generation is the number that decides whether a system is worth installing, and it is quoted inconsistently across the industry. This is what a rooftop kilowatt realistically produces in Karnataka, how that changes through the year, and what shifts it for a particular roof.
How it works
A well-installed kilowatt in Karnataka produces roughly 4 to 4.5 units on an average day across the year, which works out near 1,400 to 1,600 units annually. That average conceals a wide seasonal swing: the pre-monsoon months run well above it, and the monsoon months well below. Sizing conversations should always use the annual figure, because a system judged on a July output alone will look like it is underperforming when it is behaving exactly as designed.
| Period | Units per kW per day | Conditions |
|---|---|---|
| January - February | 4.4 - 4.8 | Clear skies, cool mornings, strong output |
| March - May | 4.5 - 5.0 | Peak irradiance, though heat reduces efficiency |
| June - August | 2.9 - 3.2 | Monsoon cloud cover, the weakest months |
| September - October | 3.8 - 4.0 | Post-monsoon recovery, clean panels |
| November - December | 4.1 - 4.2 | Mild and largely clear |
Indicative figures for well-oriented, unshaded rooftop systems in Karnataka. Actual generation varies considerably by district, orientation, tilt, shading, and system condition. Use these as a planning reference, not as a guaranteed output.
The engineering view
Five things move your number away from the average. Orientation and tilt, where a south-facing array at roughly the local latitude performs best. Shading, which is the most damaging and the most commonly underestimated. Temperature, since modules lose efficiency as they heat. Soiling, which builds through dry months. And system losses across the inverter and cabling. Of these, shading is the one that is cheap to design around and expensive to fix afterwards.
What this means in Karnataka
Karnataka sits in a favourable solar band, but the monsoon is pronounced and any honest projection accounts for it. Bengaluru's tree cover is a genuine and often overlooked factor, as is new construction: an unshaded roof today can be partly shaded in three years when the adjacent plot is built on. A shade study should consider the likely future as well as the present.
Common mistakes to avoid
Generation expectations usually go wrong here:
- Using a peak-month figure as the year-round expectation
- Assuming panel rating equals daily output
- Overlooking future shading from adjacent construction or tree growth
- Ignoring soiling accumulation during the long dry months
- Comparing output against a neighbour's system without matching orientation and age
What we recommend
Ask for an expected annual generation figure with the assumptions written down, then track your monitoring against it monthly rather than daily. A shortfall that persists across a full month is worth investigating; a single low day almost never is.
Common questions
- How many units will a 3kW system produce?
- Roughly 12 to 14 units on an average day in Karnataka, or somewhere near 4,000 to 4,800 units a year, depending on orientation, shading, and system condition.
- Why is my monsoon generation so low?
- Cloud cover through June to August genuinely reduces output to around two-thirds of the annual average. This is expected and is already accounted for in a properly stated annual figure.
- Does facing east or west ruin the economics?
- Not usually. It reduces total output relative to south-facing, but east or west orientation can suit some consumption patterns well. It should be modelled rather than assumed.
- How much does dust cost me?
- Typically a few percent, more in dry districts and near construction. Regular cleaning recovers most of it, which is why cleaning frequency is worth getting right.
- Will trees around my house be a problem?
- Possibly, and increasingly so as they grow. A shade study during design should look at the likely future canopy, not only today's.
Talk to our engineering team for a solar assessment.
We will review your consumption, roof, and site constraints before recommending any capacity.