Lest test the common claim of 170 lm/w on some locally available light fittings:

Working the calculation backwards from 170 lm/w, based on the above:

170 lumens per watt

Clear diffuser losses at 10% = 189 lumens per watt

Luminaire Optical Losses at 10% = 209 lumens per watt

Electrical Losses at 14% = 244 lumens per watt

Temperature losses from Tj 25°C at 5% = 256 lumens per watt

The brightest commercially available leds that one can but in volume sit at about the 180 -190 lm/w way off the 256 that you would need for a 170 lm/w light fitting.

See