A hard start, or super boost, or start assist are all the same thing.  They
cost about $20 and can be installed in 5 minutes or less.  Total Job:  $49
Phone: (757) 506-6488
There are a few reasons why you would want to consider having a hard start installed
on your condensing unit.  A lot of times after your ac has been sitting idle for the
winter and has some age on it, when you first energize it you here this uuugghh
sound for a few seconds and then nothing.  This indicates the compressor has tried
to start but could not so it went out on internal overload to protect the electrical
windings.  This is a great opportunity for a company to sell you a new compressor or
unit.  But, you should actually try a hard start first which increases start up torque by
500% and can get that compressor up and running.
Knowing that they just saved you thousands of dollars, companies that do try a hard start will charge you and arm
A hard start is kind of a band aid in this case and there is no guarantee how long your compressor will continue to
run.  Make sure you keep the device installed and keep your fingers crossed.  I've seen these hard starts give
compressors 2-3 years more life, so it is worth it to try... just don't pay more than you should.

Another great use for a hard start is if you have kids in the house constantly messing with the thermostat or you
have a lot of power outages.  When a unit cycles off it does so after building up very high pressures in the system.  
The unit needs to stay off for a few minutes to allow these pressures to come down.  if not, the compressor will be
under tremendous strain to try and start against high pressure and could result in damage.

A hardstart will give it the extra kick it needs to get going again.  A better solution would be to install a time delay on
your unit so it cannot start again after shutting down unless a preset amount of time has gone by on the timer.

If your system has a TXV type metering device it takes longer to equalize and a lot of times the compressor will get
a call to come back on before the pressures come back down.  Some units have a start capacitor installed for this
very reason, but many don't.  A hard start would fill in nicely here and extend compressor life.