At what inclined grade would Curiosity or Perseverance require twice the electrical power to drive compared to driving on flat terrain?

Motors have losses and friction, and compaction of soil by a rovers wheels are lossy as well. Driving over bumps/topography requires extra work going up that isn’t recovered when going back down.

The terrain that Curiosity and Perseverance traverse is varied, but is it possible to give some estimate for the incline angle that would require either one to use twice the electrical power to drive compared to a flat grade? I’m thinking mostly about the work required to raise it’s 900 kg up against Mars’ 3.72 m/s^2 gravity but maybe there are other effects as well.

Question: At what inclined grade would Curiosity or Perseverance require twice the electrical power to drive compared to driving on flat terrain?

related:

• Does the Curiosity rover really have a chance of driving to the top of Mt. Sharp?
• How are the Curiosity rover's batteries doing after all these years (and all these cycles)? Have they degraded significantly?
• Which wears out faster on RTGs; the R's or the TG's? (the radioisotopes or the thermocouples)
• How much altitude will curiosity gain by its climb now from the clay-bearing unit to the sulfate-bearing unit?
• About how long will Curiosity last on its nuclear power?