What's the best condenser fan speed control to use? Will it save on my electric bill?

Home or business unit?

A setback thermostat will save you on the bill if the place is vacant long enough every day and you set it back far enough... however for a home unit.. its unlikely to save enough to offset the cost to buy and install a VFD while the larger the business HVAC unit the more the savings would be.

These are residential units. I would like to reduce start up noise and hopefully energy consumption as well by ramping up the condenser fan speed thereby reducing inrush current. I found an ICM325HN Head Pressure Control for $85, but I'm not sure if it ramps up the fan if its calling for full load.

I also just discovered a Soft Start device by Hyper Engineering which reduces the inrush current of the compressor. Does anyone have experience with this unit?