I am looking at driving an LED panel indicator from either 230VAC or 120VAC to inform an operator that a hazardous voltage is present. I want this indicator to operate with minimal additional electronics (i.e. not converting to a lower DC voltage through a SMPS) so that it is a direct representation of the mains voltage. Most indicators are designed to operate at a single voltage level and if you undervolt them (i.e. buy a 230VAC indicator and put 110VAC into it) they are sometimes too dim to be usable. They would also not look great on the panel as I would end up with various brightness levels depending on what mains voltage is applied (I will have some 24VDC indicators also on the panel too).
Would Zener diode clamping be a suitable? Using an online calculator http://www.petervis.com/electronics%20guides/calculators/zener/zener.html for a quick estimate (assuming 10mA panel indicator, 9.4mA Iz, 100VL and 230VS) my diode would have to dissipate 1W and the resistor 1.35W which would mean they could get quite hot. Is there is a more efficient way of doing this?