From what I have read on this forum, it is important to have the refrigerant charge correct on your air conditoning system. What does an undercharge or an overcharge condition do? For instance, would either condition cause your utility bills to be more? Or would either condition damage some of the equipment? Would there be less problems when you have a TXV on the evaporator coil?
Antyhing that alters the performance will alter the cost of the unit running. Yes, the systems require that they not only be charged properly but installed properly. Airflow is the most common problem which will make the charge incorrect.
A TXV is no better than a piston when it comes to overcoming problems. It may hide problems but ultimately the symptoms change.
"According to the best engineering data available, the performance loss using a TXV metering device is about 5% if the refrigerant charge is off by plus or minus 20%."
"The performance loss using a fixed metering device (capillary tube or accurator) is about 15% to 20% if the refrigerant charge is off by plus or minus 20%."
1.) Don't have time right now... but basically (efficiency and shorten equipment life).
4.) Can be, but not always.
Thanks, go_redskins. The link of buildingscience.com was very informative.