Compared to nuclear fusion, how efficient is the energy conversion process during accretion onto compact stellar remnants?

Answer

It is far more efficient

The energy differential between a particle's initial orbital energy and the energy released when it crosses the final stable orbit near a compact object results in an energy release that is far more efficient than that produced by nuclear fusion.

Compared to nuclear fusion, how efficient is the energy conversion process during accretion onto compact stellar remnants?
Geologyprocessplanetmassaccretion