Reply to post:

But how does it compare to the Energia rocket?

The two flown Energia rockets had 6.5 million pounds of thrust at takeoff, with a capability of putting 100 tons into low Earth orbit. The Saturn V had 7.8 million pounds of thrust at takeoff, with a capability of putting 130 tons into LEO.

So, as the BFR is about twice a Saturn V, it's about 2.6x an Energia. Approximately, give or take a bit.

There were some planned Energia configurations with higher takeoff masses and thrust levels, but those didn't get off the drawing board.