Another thing to consider for adding soft starts is that they could void your warranty.
I have Dual Stage Lennox XC21s and had a Licensed/Trained/Certified/whatever Lennox technician on site to install soft-starts. But he called HQ and Lennox told him that they would not allow soft starts to be installed on my equipment otherwise I would void the warranty on the condensers. They added that:
1) Lennox Industries had no documented instance of anyone ever installing a Soft Start on their current generation of residential compressors (includes all of their current Merit, Elite, and Signature lines).
2) Soft starts are not recommended on Lennox's older, dual stage equipment since the soft start cannot properly learn the in-rush current demands of both the single and dual stages
Wow that's crappy to find out. We have an old 2004 Carrier 5-ton split unit, and the manual for it has what they call Compressor Start Assist under Accessories for it. From what I understand our model will work with the SureStart but nice to know the manufacturer has its own part as well.
We will eventually be replacing our unit and will keep in mind that we don't want a two-stage a/c for this very reason. Anyone know if the reason the 2-stage won't work with one would also apply to a variable speed a/c unit?