a little help with capacitive power supply values

[dhouston]

But how efficient is a xformerless supply if it's not "precisely loaded"? Input current is always the same regardless of load! And unless that fancy X2 cap is sized exactly to the needs of the circuit, it looks like that zener is gonna be dissipating a good dose of heat.

I have measured several X10 modules, when idle, to see how much power they waste. It's not much. http://davehouston.org/x10-power.htm

Some of the highest use transformer supplies. SMPS tend to have the best efficiencies.