That might be true for airlines, but for $500 hamburger runs, I doubt it is true. Or the ratios are way off.Hybrid is the current best efficiency for cars. The early hypermiling vehicles would use vehicle inertia to store energy, they accelerate at peak engine efficiency, then shut the engine off and coast down. Now, you can just go buy a hybrid battery car tat cycles the engine without varying forward speed. Aircraft don't need a huge surfeit of power like cars do, so hybrid is a lot less benefit. In fact, aircraft engines maximise efficiency at around cruise power. Yes, extra takeoff power is useful, but making the added complexity of hybrid worthwhile is a lot harder. Has anyone else considered JATOs?
Often I see comments that 2-3 hours is all the bladder for the pilot can handle. As such, a twenty minutes in climb for two hours in cruise is 1/6 of the total time. That is a rather significant portion, and hybrid would very well for this. Further, think about engine heat. Cooling drag is a major factor, so if you can design the cooling to only deal with cruise, and not the higher temps in the climb, you can likely decrease the total drag of the plane.