True, you can go higher than say 50%, but it's relatively expensive. Generally you won't make that extra investment back on power savings, so for most people there is no use for going above 50% right now. I calculated that the price of the COBs (PAR per $) doubles if I wanted to go from 50% to 53.4%. I pay around a euro per watt per year so it would take me 7 years to get back that extra investment in power savings (if I have the flowering light on for 12 hours every day of the year). BTW If you want to go for high efficiency (ie above 50%), the Citizen COBs aren't very good. I think then you would better (cheaper) off with Cree COBs. Citizens are cheaper when you push them a bit harder. Although I estimated that on the version 5 Citizen's. Perhaps the version 6 COBs improved enough to raise that bar a little.