Volt-amps and my bathroom light transformers

 

I need transformers to get the bathroom lights down to 12V for safety in a wet environment. I notice that whilst the power of the bulbs is measured in Watts, the power of the transformer is measured in VA or volt-amperes. The issue is that the transformer contains inductance coils. With AC, they become electromagnets whose polarity is constantly changing. This means a rate of change of flux inside the coil which generates an emf by Faraday's Law. By Lenz's Law, it must be a back emf to oppose the motion that caused it. In other words, it effectively reduces the flow of current as a resistance would do. It is not resistance because it is not that mechanism so we call it reactance instead. It puts the voltage  out of phase with the current. This means straight volts x amps = watts doesn't work here. Using VA makes that distinction.