I apologize - the Teszla fixture contains LEDs. I thought we were discussing the Tesla induction fluorescent lamps.So many factors come into play... Reflector construction (material, reflector), wattage, age of lamps and on and on. I will say Tesla's induction fluorescent lamps can potentially last much longer that conventional fluorescents (due to lack of electrode degradation, sputtering, etc.) A PAR meter would be an excellent investment.