this is what i usually copy past when it come to choosing a light:

250W hps will scale for a 2x2 or 100W to 200W led

250W hps or 315CMH is enough for a 2x4 or 200W to 450W led

400W hps will scale for a 3x3 or 300W to 500W led

600W hps will scale for a 4x4 or 500W to 860W led

1000W hps will scale for a 5x5 or 700w to 1000W leds