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Which is Better - an Electric or Belt-driven Fan?

2010 February 27
by admin

This debate is as old as the electric fan itself. We manufacture both, so we're pretty unbiased on this topic. In fact, we created the first high-performance belt-driven fan in 1962, and we were the first to introduce an aftermarket electric fan to the U.S. in 1978.

We'll jump right into the heart of the matter: An electric fan is the better performance solution, freeing up maximum horsepower and mpg. But it's not always the better cooling solution. The full answer to this question is that both electric and belt-driven fans have their place. Which one is better depends largely on the specific application.

All fans consume energy to spin. Belt-driven fans use mechanical energy directly from the engine. Electric fans rely on electric energy from the battery and charging system. But in cooling, what makes a good fan is optimum airflow for cooling with minimum energy consumption (for maximum engine power and fuel economy).

Electric Fans

An electric fan completely removes the mechanical load of spinning the fan from the engine. It places an additional draw on the electrical system, but this is a more efficient means of spinning a fan, and it has a smaller impact on engine drag. Between the two types of fans, an electric fan offers an improvement in power delivered to the wheels.

Removing a belt-driven fan that mounts on the water pump reduces the load on the pump. This can lengthen the life of the bearings in the water pump.

One huge advantage that electric fans offer is flexibility in when they are turned on. An affect that most people don't consider is that your engine can come up to operating temperature more quickly with an electric fan because the fan doesn't turn on until a specific temperature. This is nice in the winter time to warm up your car more quickly, and it's critical in drag racing where you want just the right amount of engine temperature of optimum performance. An electric fan can cycle on and off, reducing the electric load. You can wire them to come on when the air conditioning is turned on to maximize the efficiency of the air conditioning system. For a 4x4, you can also add a manual kill switch to turn the fan off during a mud run or water crossing to minimize pulling more than just air through your radiator.

Another advantage for electric fans is packaging. We don't mean putting it in a box, but rather how it fits underhood. If you're making engine or cooling system changes, the original belt-driven fan might not line up any longer, or the factory fan shroud might not fit. Electric fans are designed to mount directly on the radiator, usually providing for the most compact and easy installation possible. They can also fit in very tight spaces. A belt-driven fan will typically require at least 3 ½ inches between the water pump and the radiator, while our Low Pro electric fan requires only 1.09 inches at the center where your pulley is. For vehicles where the engine and radiator/fan shroud move a lot - like in off-roading - an electric fan eliminates the possibility of the fan hitting the radiator or shroud.

Finally, if you're installing a custom radiator, adding an electric fan is easy and will clean up your underhood considerably. In fact, we offer a line of aluminum radiators that are available with an electric fan that is optimized for the radiator.

Belt-driven Fans

If your vehicle has a belt-driven cooling fan and you're not making major changes to the engine or cooling system, the simplest thing to do is to keep a belt-driven setup. You can, however, increase your car's horsepower and fuel economy without giving up cooling capability by using one of our high-performance flex fans.

Since a belt-driven fan increases speed (and airflow) with engine speed, it can move more air at higher engine rpm - usually above 2,400 rpm - than an electric fan. Conversely, electric fans move more air than belt-driven fans at engine speeds below 2,400 rpm in typical applications.

One major downside of belt-driven fans is parasitic loss. It simply takes more energy to spin a belt-driven fan than it does to produce the electricity needed for a comparable electric fan.

Here are some of the applications where we would recommend a belt-driven fan. They are better able to pull air through a restrictive cooling unit. If you have a four-core radiator with an inner cooler, air conditioning condenser and transmission cooler stacked in front, a 7-blade flex fan along with a proper-fitting fan shroud will be a great choice for cooling. A belt-driven fan is also a good choice if you are having a cooling problem at higher engine rpm. A lot of off-road vehicles drive at slow speeds with high engine rpm. This can build a lot of heat without any natural airflow through the engine compartment. A thermal clutch fan will make use of the high engine speed to move maximum air.

Which is Right for You?

That's the key question, right? Here's our advice: If you are looking for a performance upgrade then the electric fan is for you. Make sure the electric fan covers 70 percent of the radiator core and moves enough airflow for the engine size (a rule of thumb is at least 2,800 cfm for a 5.0L engine). The electric fan would be a cooling solution for vehicles that typically drive at low vehicle speeds with low engine rpm, such as cruising. If you have a 4-core radiator or towing heavy loads then we recommend you stick with a belt driven fan. Finally, if you have a cooling problem, watch this blog for future articles that will help.

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8 thoughts on “Which is Better - an Electric or Belt-driven Fan?”

  • How to Choose an Electric Fan « Flex-a-lite Blog April 24, 2010 at 4:09 am

    [...] The first step is to make sure you want an electric fan. Click here to read our article on electric versus belt-driven fans for more information on that topi... [...]

  • Jordans 1
    Jordans 1 April 29, 2010 at 2:16 pm

    What a great blog! It's a pity that i can't find your rrs address. If you can offer rrs subscription service, i can track your blog easier!

    • therealcoleq
      therealcoleq May 2, 2010 at 3:46 am

      Thanks for the kudos on this Web site. As for the RSS feed, I'm not sure what sort of difficulty you're having. There is an RSS feed link on the righthand side of the page for posts. The URL is: I have noticed that this WordPress link does not work too well in Google Chrome. If you're using FireFox or Internet Explorer, you shouldn't any trouble.



  • Replacing the clutch fan with an electric one? - May 6, 2011 at 2:16 pm

    [...] makes both engine-driven and electric fans, so they are not biased (at least I don't think so): Which is Better The interesting thing I read that is that they say a sub-5.0 V8 needs about 2,500cfm, while a 5.0+ [...]

  • Ray
    Ray July 23, 2012 at 2:18 pm

    Hi I have a Chevy Silverato with a 5.3 litre and pull a 5th wheel with a GVW of 8000 lbs,would a flex fan help fuel economy and keep my engine cooled properly.Thanks for now.Ray

    • therealcoleq
      therealcoleq December 11, 2012 at 10:56 pm

      We make a 7-blade flex fan (PN 1817) that would most likely work well in this application as long as you have it properly shrouded. We say "most likely" because there are a lot of variable. Are you pulling the Baker grade in California in July or mostly driving through the cool flat lands of central Canada?

  • Mike
    Mike December 11, 2012 at 6:45 pm

    Hi, I have a modified 65 Ford Ranchero with a 302 (hydraulic cam, roller rockers, etc). It has a belt fan and the car is fine at speed, running at about 180 degrees even with the AC on. But at car shows, cruising, or even stop and go in the summer time, it climbs fast to 220 or more. Will an electric fan really help with that? I envision something like a whole house fan that would pull air through the radiator and give the effect of moving faster than I am when cruising. Am I on the right track? Does the number of CFMs make a difference? Thanks for the advice

    • therealcoleq
      therealcoleq December 11, 2012 at 10:25 pm

      You're on the right track that an electric fan will overcome the overheating tendency at slow speeds and at idle. The '65 Ranchero has a pretty small radiator. You'll need to do some careful measuring to see what electric fan will fit it best. You can find an article on how to measure for an electric fan by clicking here. Yes, cfm makes a difference. It is a measure of how much airflow an electric fan creates. You'll need more air to cool a larger or more powerful engine. With your engine combination and the tight engine bay of an early Ranchero, you'll want 3,000 cfm of airflow or more with a fan that is fully shrouded -- covering as much of the radiator as possible -- to replace the belt-driven fan on the backside of the radiator. In addition to better cooling at slow speeds, this lets you remove the belt-driven fan to free up some horsepower and improve fuel economy. If that's not possible, another solution is to keep the belt-driven fan and add an auxiliary electric fan to the front of the radiator. An extra 2,000 cfm of airflow with one of our auxiliary electric fans will help reduce temperatures at slow speeds and idle. Our Trimline 16-inch electric fan is a good example with 2,215 cfm of airflow. Smaller diameters are also available.

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