The requirements of 80 Plus certification are greater than or equal to 80% efficiency and 0.9 power factor or better at 20%, 50% and 100% load for all rated AC input voltages. The OCZ ModXStream-Pro 600W didn't quite meet the requirements of its claimed 80 Plus certification with an efficiency of 77% at full load on 110VAC. The results at all other stages are satisfactory and an efficiency of 84% at 230VAC is very good. These results are very typical with a peak efficiency at approximately 50% of rated full load, excellent power factors at 110VAC and excellent efficiency at 230VAC. The power supply gets an overall pass at all stages, because it meets the requirements of the ATX12V V2.2 specification for ATX power supplies.