Both NEMA and ZHAGA are international standards for physical connectivity between external controllers and streetlights. The NEMA standard has its origins in the USA, and was defined several decades ago by the ANSI, which is the North American organization in charge of coordinating and regulating the different technological and industrial standards and regulations in the USA. Later on it spread to some European and Latin American countries. ZHAGA, on the other hand, is a more modern standard (2018) and was originated in Europe. It was published by the ZHAGA Consortium, and later on it spread globally. Unlike NEMA, ZHAGA has been more ambitious in its objective of standardizing interoperability, and focuses not only on the physical conection but also on the protocol to exchange of information between the luminaire Drivers and controllers by the launch of the ZD4i standard in partnership with the DALI Alliance. Furthermore, recently, the ZHAGA Consortium has reached an agreement with ANSI under which the logical standard for information exchange between the luminaire Driver and controller will also cover NEMA sockets in the USA.

In practice, the truth is that the ZHAGA luminaire socket is significantly smaller than NEMA socket, which allows it to be adapted to practically any luminaire without impacting its aesthetics. In addition, the NEMA standard requires that the external power supply of the luminaire firstly goes through the controller and then the controller will power the luminaire, with the consequent risk in case of overvoltages that affect the life of the controllers, causing a higher rate of breakdowns. This does not happen with the ZHAGA standard, since the controller is powered by the luminaire Driver (12/24VDC), with the consequent advantages in terms of lifetime extension and lower failure rate.

For all the above reasons, the ZHAGA standard, and particularly ZD4i (ZHAGA socket and DALI2-D4i LED Driver), are undoubtedly gaining ground and becoming the default standard, especially in Europe. It is important for lighting managers to take this into account when choosing the luminaires and controllers to be used in their projects, so that they avoid installing solutions that may become obsolete during their lifetime.