Select a voltage regulator which principles should be followed?

Gechy Electric suggest that when you buy the regulator select three times larger than the actual use of power regulator, because regulators in practical work should bear the impact of surges and inductive load electricity (such as refrigerators, air conditioners, motor)? Then buy regulators should follow what specific principle?

First, before the purchase must consider the future business expansion, whether need additional equipment later, the regulator needs to set aside expand capacity and so on. 

Second, pay attention to the mains supply voltage value exceeds the optional regulator specified input voltage range, the three-phase electrical voltage is above 10V difference. 

Finally, no matter it is a stand-alone package or the entire plant infrastructure, the regulator should set aside a certain expansion capacity in order avoid 100%t load factor. General regulator max load rate of 80% is more appropriate. 

In addition, automatic voltage regulator have desktop, wall-mounted & floor style etc. Based on the location of the installation, usage & ability to select the appropriate installation style.