if a motor, for example, is rated at 80% efficiency it is only using 80% of the available (100%)power coming into the carwash
Wax, thats not what efficiency is.
Efficiency in this context means how much of the power/work coming into the
pump (not the carwash) is transformed into the desired result, in this case water pressure. A couple really simple examples:
1) My boiler for floor heat burns gas. What I want is for 100% of the btu's (heat) produced from burning that gas to end up in the bay floors. Unfortunately some heat goes up the chimney with the exhaust, some heats up the boiler itself, some of the gas doesnt combust completely... etc. So in the end about 30% of the gas I pay for doesnt end up heating my bay floors. That would be 70% efficient.
2) Incandescent light bulbs radiate both light and heat waves. The heat is "wasted" if your desired result is light, therefore the bulbs are not 100% efficient.
It just doesnt seem likely to me that adding MORE equipment would make my equipment more efficient.
Am I 100% efficiently correct? I am not an engineer, so I dont know.
For simple things like a light bulb, water heater, motor/pump: I think my basic understanding is functionally accurate.
For things like a car, putting a computer in there can optimize settings, fuel usage, etc based on your driving patterns. But thats a custom & complex system, thats not something you can plug in to any device.
I also know that electronics last longer (etc) if they get a "smooth" power supply; but I dont know if that makes them more efficient.
Anyway, theres my 2 cents. Hopefully someone who knows what they're talking about will chime in, but fundamentally I think Whale hit the nail on the head.