This is a wide-spread misconception about language, and you are not to be blamed for it. The underlying idea is that one requires some caloric quantity to do anything (you're always doing something, until you're dead). Then maybe is take more energy to do X than it does to do Y. But there is no way to measure how much energy is expended doing a specific thing. The underlying idea of measuring calories burned is based on CO2 output, but this is a crude technique that distinguishes running 10 minutes with a sack of rocks on your back from sitting in a chair for 10 minutes, but doesn't distinguish uttering a sentence in Hindi from uttering a sentence in Assamese. From the scientific POV, there's no basis for saying that one language versus another requires more caloric energy.
Subjectively, people may report that they have a hard time saying things in one language compared to another. This is generally because of differences in fluency, level of experience, and certain socio-contextual facts of the language. A math professor at U. Dar es Salaam once pointed out why it was necessary to teach advanced math in English rather than Swahili – mathematicians don't write proofs in Swahili and the terminology is not natively Swahili (he wasn't interested in finding a way to Swahilize his lectures).
It is somewhat well known that Hindi has many regional varieties such that you can often often guess from a person's accent whether their first language is Tamil, Hindi or Punjabi. The question of effort required to speak Hindi needs to be articulated into questions about speaking "standard Hindi" versus "local Hindi", same with English. It is generally easier to speak the language that is locally used, and your feelings about effort in speaking Hindi may reflect lesser familiarity with standard Hindi, especially spoken as opposed to written. If you happened to speak Goalpariya Assamese as your native language, you might experience a similar struggle in speaking standard Assamese.
It's never about "energy-efficiency" of a language, it's always about the difficulty that an individual faces in using a particular language, which generally reduces to the question of how well they know it (which version?), how often they use it, and for what purpose.