What's the ROI for Regen Drives?

We never seriously considered line regen braking on our centrifuge systems (VFD-driven ac motors) because of initial cost. We dump the energy to choppers. We're being told that partly because of hybrid car advances and demands in industries with high energy consumption, it's become much more cost-effective. There's interest in both new installations and refit projects. What can anyone tell me about ROI these days to use regen drives?

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