Are you even sure that this is an electronic ballast? It could have both a MH and an HPS ballast with a small computer to determine the lamp type inside. How heavy is it, and have you opened it?

Are you even sure that this is an electronic ballast? It could have both a MH and an HPS ballast with a small computer to determine the lamp type inside. How heavy is it, and have you opened it?

It is very obviously an electronic ballast, their logo even boldly says "Lumatek Electronic Ballast".

No computer required. it could simply either drive a bit incorrectly (but still close enough) either lamp, or for the better stuff, some saturation based power regulator (like CWA concept but not necessarily real constant current). Or the simplest, taps and switch

No computer required. it could simply either drive a bit incorrectly (but still close enough) either lamp, or for the better stuff, some saturation based power regulator (like CWA concept but not necessarily real constant current). Or the simplest, taps and switch

How could taps and switch me electronic?

If it was magnetic

If it was magnetic

Maybe this is electronic because they want more efficiency, or lower noise. But why?

In medium and higher power HID the efficiency gap between Magnetic and Electonic is small even for 120V, on 230V the Magnetic ballasts are often more efficient than the Electronic. That is because Magnetic are very efficient on big scale - As extreme example, MVA-range substation transformer is typically 0.98..0.99 efficient - No electronic can do that. At 400W i think efficiency considerations can be ruled out

Noise too, modern Magnetic ballasts can be made dead silent

I think it might be up to cost (Cheapish Electronic components from China cost less than the Copper and Steel in a comparable Magnetic ballast), or to implement the compatibility with different lamps

There are other aspects:
With electronic, you may practically eliminate all flicker, so the lighting may be used along with machinery where the stroboscopic effect would be a safety hazard.
Electronic use to be lighter for the same power, so allow fixtures to be mounted on places, where it was not possible. And still feature 95+% efficiency.
It usually offers way more extensive diagnostic and protection capabilities, so significantly reduce many dangerous failure modes (mainly lamp explosions due to either thermal runaway or just EOL, fire hazards from rectifying lamp faults,...).
And mainly allow specific regulation schemes, so opening the room for lamp chemistry or designs, which are better performing, but would be too unstable on a simple magnetic ballast (the first example were the white SON, where the electronic still had used rather classic format inductor).

I wonder how much applies to horticulture, AKA growing plants without much natural sunlight.

Maybe the mass (either the roof does not have to support that heavy ballasts, or in case of remote ballasting the ballast cabinet won't be that heavy).
And maybe the safety...

Maybe the mass (either the roof does not have to support that heavy ballasts, or in case of remote ballasting the ballast cabinet won't be that heavy).
And maybe the safety...

It has built in circut breakers.