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Cooler Master Real Power Pro 1,250W Power Supply Review

Author: Lee Garbutt
Manufacturer: Cooler Master


The Cooler Master Real Power Pro 1,250W power supply is rated for a combined, continuous output power of up to 1,250 watts at 50°C operating temperature (internal case air temperature).  That’s important as some less reputable manufactures limit their power supply’s advertised capacity by specifying a lower operating temperature (25°C) in the fine print.  The PSU includes universal AC line input (automatically adjusts the AC line voltage) and active PFC, which makes the unit more environmentally friendly to the local power grid.  The Real Power Pro PSU is 80PLUS certified and was designed to provide up to 87% efficiency during normal operation.

Cooler Master has chosen to use six +12V rails instead of delivering a single, large +12V output as many newer power supply manufacturers are electing to do.  This is accomplished by implementing current limiting circuits into the design to conform to the 240 VA maximum guidelines – no single output should exceed 240 VA (12V x 20A = 240 VA).  In addition, the three +12V outputs that are dedicated to PCI-E graphics connectors (+12V3, +12V4, and +12V5) are each rated at 28A on the Real Power Pro to prevent potential power distribution problems from occurring when using multiple high-end video cards.

The following tables list the Real Power Pro 1,250 PSU specs from the Cooler Master website.

Input Power Limitations

Whenever we’re dealing with a PC power supply that has a DC output in excess of 1,000 watts, the perspective user should pay attention to the AC line input requirements.  This is particularly important for North American users as we are typically limited by our 115 VAC, 15A residential wiring circuits. 

The Real Power Pro 1,250W power supply comes with a sticker over the main power receptacle warning users that it is dangerous to use the Real Power Pro 1,250W power supply if the wall outlet is not specified for 125V/16A or 250VAC/10A.  While this warning primarily applies to worst case operating conditions (maximum load with minimum line voltage) it should not be lightly ignored.  Unfortunately the majority of residential circuits in NA are limited to 15A.  Yes, we also have 120V/20A circuits, but they are typically used in the garage, basement or kitchen.

AC Watts = AC Volts x AC Amps x PF

At maximum load (1,250W DC output), the Real Power Pro 1250W power supply will pull approximately 13A from an 115VAC circuit (assuming 82% efficiency and PF~1).  This is well within the rated capacity of a 15A circuit, but don’t expect it to power much else.  However, if the AC line voltage happens to be very low, the AC current draw will increase to deliver the same power.  If the AC line voltage dropped to 100V, at maximum load the Real Power Pro 1,250W power supply will need slightly more than 15A to keep delivering 1,250W DC output.  However, this isn’t a very realistic scenario.

Under normal operating conditions, the PSU should not exceed the capacity of a standard 15A residential circuit.  Even a heavily loaded, high-end gaming rig with multiple video cards will be hard pressed to pull 1,000W DC, which translates to roughly 10.5 Amps on the AC side.  And just because a power supply is rated for 1250W doesn’t mean you should operate it at that level (I use 60~70% of maximum load when sizing a power supply).

Another point worth mentioning is that the CM Real Power Pro 1,250W power supply is not designed to deliver its maximum rated output capacity when the input line voltage is reduced to 100V or less.  Our good friend Paul Johnson over at [H] gets the credit for uncovering this feature during his extensive testing.  Paul found that the Real Power Pro 1,250W PSU can only deliver approximately 75% of its rated capacity (938W) when operating on a 100 VAC line.  But once again, this isn’t a very likely scenario and we found during our testing that the Real Power Pro 1,250W PSU had no problem delivering its full rated output capacity when operating on 115 VAC mains.

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