Usually in a residential rooftop project, a 3 Kw rooftop solar can ideally generate upto 10-12 units per day. The daily generations are usually dependent on the local weather. Usually when there is good sunlight throughout the day, you can get the best generation (if your solar panels are clean). During clouds, rains, the generations reduces. So a system which can generate around 12 Kw per day can also generate 5 kw or 7 Kw during clouds/rains. The generation also varies season to season, depending on the quality of sunlight and availaility of sunlight.