To give you some idea what to expect, the A51 should dissipate 165W @ 30% so that is about 50 PAR Watts. Then there are reflector and lens losses call it 15% so you get 42.5 PAR Watts in the canopy.
The 400 HPS with brand new bulbs dissipates 400W @ 34% so 136 PAR Watts minus 25% reflector losses so you get 102 PAR Watts in the canopy. So the 400 HPS gets more than twice as many photons into the canopy assuming a brand new bulb.
What if I told you ,that in fact it is the A 51 with its 42.5 PAR Watts,that
probably has about the same if not more photons (in absolute number of photons =umols ) ,
than the 400Watt HPS ?
Or if it is not The A 51 ,it can be another led light ...
Simple physics there ....
The longer the wavelengths ,the more photons for the same amount of given radiant power ...
HPS is mainly green and yellow wls ....
Leds are (usually ) heavy in red wls ...
....
1 watt red light contains almost double amount of photons than 1 watt of blue light ....
Guys, you 've to relax a tad ,with the efficiency numbers and records ..
Or the PAR watts or Horsepower or what else...
It doesn't work that way ...Not only that way ...A whole lotta more to be taken into consideration than just power/PAR watts /efficiency of the x led ....
No ...
Leds are way powerfull and versatile illumination regarding horticulture ..
HPS and MH are just ...more familiar ..To put it this way ...Auto-pilots ....
Leds are another story ....
300-400 Watts of them can beat the yields of any 600-1000 Watt HID light ...
But not on "Auto -pilot " .
It takes a lot more ...
Only for the brave ...