Let's just answer the question posed in the headline right off the bat: No. Giant, floppity mushrooms will not be the basis of a secondary power grid in India in any conceivable future I can visualize, as delicious an idea as it sounds.
But seeing as exploiting organisms like algae to create electricity is an obsession among some futurists, let's take a moment to consider Tobias Revell's sci-fi story of how slum dwellers in Mumbai flipped their lives around with a handful of genetically mutated fungus. A graduate of the outlandish-idea factory that is London's Royal College of Art's Design Interactions program, Revell has theorized an alternate future seemingly ripped straight from the wet neural material of Michael Crichton.
It begins in Amsterdam, where shady bioengineers are altering the DNA of fungi to create huge organisms with narcotic properties, sort of like Godzilla 'shrooms. The plan is to chop up these primo porcini and sell them as drugs on the black market, but things go awry when somebody makes off with a sample and disappears. The Amsterdam crime syndicate should've known better: It's just smart drug-business practice to make your lab workers titrate and pipette naked.
The sample eventually surfaces in Dharavi, a Mumbai slum full of civil-war refugees that has little semblance of law and order. I'll let Revell explain the rest, via his website:
Sometime later a cache of biological samples appeared through the criminal networks of Mumbai, in the vain hope that it might provide new marketable narcotic opportunities. The collective drive and expertise of the refugees managed to turn theses genetically-engineered fungal samples into a new type of infrastructure - providing heat, light and building material for the refugees. Dharavi rapidly evolved it's own micro-economy based around the mushrooms.
So it's a feel-good story of a community pulling itself up by its sandals to become self-sufficient on humongous, building-shadowing lichens. What's not to love about this idea, aside from the thought of one of these monstrosities breaking off and crushing a dozen families on the street?
Revell's actually made a decently produced faux-documentary about Mumbai's mushroom boom, which you can watch below. After viewing it, you probably won't be surprised that, aside for inflated woodland flora, Revell lists his hobbies as "theoretical physics, explaining theoretical physics, word games, objectivity in conspiracy theories, failed architecture, cryptozoology, unexplained phenomena, forgotten events, music, paradoxes, video games, clever jokes and cycling."