It depends on the total capacity of solar panels and your electricity meter capacity. In most states the maximum capacity of rooftop solar a person can install in upto the total capacity of your power connection (meter). As per the MNRE benchmark price, the total cost for a 3Kw system is Rs 1.45 lakh. However, the final cost of the project is mutually decided by the consumer and solar vendor. So despite the MNRE benchmark price which is not mandatory, the solar project vendors install a 3 Kw system often at higher price ranging from Rs 1.5 lakh to Rs 3 lakh based on the technology, reputation of the vendor, services it is providing and other parameters.