I agree with the electric pump, but it's too pricey for me. I was thinking about doing one for a problematic motorcycle I have. The pump runs coolant all over...through the frame & around the engine.
What newer BMWs have electric coolant pumps? The only ones I've been able to find are the crap aux coolant pumps on Passats.
Esprit Aviation...you're forgetting alternator inefficiency, but your point is still valid.