Growroom Design and Setup

How do I power 12v computer fans?

Quiet, low power and surprizingly efficient, computer fans are an ideal cooling option for smaller cabinet grows. The only problem is that most computer fans are 12v and not 120v! How do I run a 12v fan on normal household power? 

  • Computer power supply 
    (A 145 watt computer power supply is over-kill for a 5-20w fan. Try for something small, like a 75watt or 100watt supply). You could drill holes and mount the power supply inside your cabinet. turn the power supply on and off with the power switch on the back. 

  • (Carpe-Nox) … if you have any old cell phone chargers around, they use 12v, same that a pc fan uses, just splice the pc fan wires 

  • [Editor’s note: 120v computer fans can be found. Add a pigtail to your fan and voila.] 

    Fan ideas 


    ex.) 120mm, 90CFM fan for $11.95. it only uses 5.4 watts - a perfect exhaust fan. 

    ex.) 80mm computer fan that is thermally controlled. $5.95 - the hotter your cabinet is, the faster it spins. 

    (Jakestone) PCs frequently run their 12V fans at voltages below 12. 7 Volts is very common. Much below that, there can be an issue of having enough starting voltage to get the fan going. The volume of air being moved is reduced, but so is the noise. 

    (Jakestone) El cheapo $3 fans are often significantly louder than better fans (say 5+ db) and have a dirtier sound (less whoosh and more whine/ticking). High-end fans generally go for between $10 and $15. Computer power supplies are notoriously noisy (especially cheap ones).

  • (Jakestone) In general, a larger diameter fan moving a given amount of air will be quieter than a smaller diameter fan moving the same amount of air. So for example, one might buy a 120mm fan that moves more air than you need to move at 12V and run it at 7V instead of running a 80mm fan at 12V. The downside for cabinet growers might be the need to light-baffle a larger hole.

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