Since you’re running over 2000 kms a month, you can consider buying a CNG car. We would have recommended a hybrid as well, but the most affordable hybrid, the Toyota Urban Cruiser Hyryder S, is around Rs 1.5 lakh over your maximum budget of Rs 15 lakh.
In CNG, we would recommend the Maruti Suzuki Victoris, either in the LXi or the VXi variant, depending on the features you are looking for. The Victoris is a well-engineered car, and the solution Maruti Suzuki has come up with for the CNG tank position under the boot floor makes the Victoris CNG very versatile. In terms of boot space, the compromise is minimal, which is important since you go on a long drive once a month with your family.