Unless you're looking to work outside of India as a development practioner, I would recommend against obtaining a 'development studies' degree in any of its forms. These degrees are useful to an extent for people from NA who are trying to work for INGOs or other international organizations, mainly for the networking aspects. But I would think it odd for someone from a country such as India to obtain one in order to go back and work in their home country.
You already have a strong profile to work in the field of energy and the environment in India. As such, it seems your best option would be to get a degree to 'future-proof' yourself against possible competition. By this I mean you should look at the degree programs you can attend from top tier schools in the field internationally. In terms of environmental management, those would likely be the MEM programs from Yale or Duke. In terms of energy/environmental policy issues, those would likely be Stanford IPS, Columbia SIPA and to a lesser extent, UT Austin. My thoughts are based both on the quality of the curriculum as well as the 'signalling potential' of the degree. Yale is probably your best bet, with Stanford in second, although this will mostly depend on which field you're most interested in (environmenal management or public policy).
You have a very good shot of being admitted into any of these programs, but it will likely come down to your essays and references. Make sure to craft a strong essay based on why you would want to attend the specific school and what you intend to do once you've obtained the degree. Flexibility between being a development practitioner and consultant is fine for an internet forum, but you'll need to be much more specific in your personal statements - I'm saying this as someone who was admitted to all of the programs I mentioned, and with a background in environmental management and energy issues (in both developed and developing countries).