A physicist wouldn't like the expression "powering gravity". To speak of powering gravity would be a lot like "powering a hill". It isn't the hill that "gets powered" but the mass that gets raised aove the bottom of the hill, thereby gaining what we call potential energy. The higher we raise it the greater the potential energy. We do not thereby create the energy, but convert some other form of energy. For example we might burn fat to power muscles to raise the mass, converting chemical energy into gravitational potential energy. 

If we concentrate mass in one place, say piling up rocks to form a massive planet, it distorts space in such a way that any body passing it in free fall (nothing else pulling or pushing it) its path bends towards the mass. Would you like to say that the mass powers gravity? Suit yourself, but the physicist still would have some very snappy things to say, even if only under his breath.

The simple truth is that nobody yet knows for sure where gravity comes from.  If you do, write a paper about it and ask your friends to tell the Nobel Prize committee.

But we do know that mass and energy are really very much the same thing, or aspects of the same thing.  Think of mass as a kind of very concentrated form of energy.  If you convert mass to energy,  just a little mass yields a whole lot of energy.

Gravity is that tendency for mass-energy to be attracted toward itself.  Einstein gave compelling reasons to believe that the mass-energy distorts the local geometry of space-time around it in such a manner that the mass-energy moves through space-time in just the way we call gravity.  Every experimental test of his ideas has supported that point of view, but it has proven very hard to reconcile his mathematical description of the situation with that of quantum mechanics.  So, the question remains open.

So you might say that "what powers gravity is the presence of mass-energy in space-time."  That sounds like you know what you're talking about and makes for impressive party chat, when really, all you know is that the math seems mostly to be working out under certain circumstances but not all of them, and nobody knows why.