This chart helps you visualise the power of a render farm. Use it as a rough rule of thumb or guide to how much of a speed up you'll get in a render farm with n computers, vs just a single computer. Note that the curve in this chart holds for any render farm, blender included. It's generated from the formula t = T/n (where T, or the total render time on ONE computer is 10 seconds, t is the time for the same animation rendered on a render farm with n computers).

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The chart above shows the ideal or theoretical speed up of a render farm, notice how the render performance changes as you add more computers to it. This curve applies to stills and animations. Here's a summary of the important points.

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1. The curve above is for a hypothetical render farm rendering an animation. The animation has ten frames, which take one second each. The time the render farm takes to complete this animation is shown on the vertical axis.​

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2. On the horizontal axis, the number of computers in the render farm is shown, which increases, from 1 to 20. You can see the render time falling as a result.​

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3. The shape of the curve is dictated by how many, and of what hardware each computer in the render farm has. In this example, every computer in the farm has the same hardware, and the delays due to the network are assumed to be zero (note that your render farm could have a mix of hardware, and so the results would be different in this case).​

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4. Importantly, when adding the first few computers, the decrease in render time is much, much larger than towards the end of the curve. This means, as you add more computers, the speed improvements get smaller and smaller.​

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5. The final point is that, for your projects, there may be an ideal size of render farm based on how much money you're willing to spend. Each computer you add costs money, and the biggest gains in performance come from the first few computers you add. Of course if you're building a render farm from computers you have already bought, then good news, every computer you add will increase your render performance.
 

There are some caveats though, so far we've not mentioned electrical power consumption. Usually, when people use our render farm software, they are doing so on machines they already own and want to extract some more use from them by combining their hardware into a render farm. 

 

Usually, as an artist, you'll likely be upgrading throughout your career to the latest spec hardware you can buy.​ The slower, older computers end up being either sold, shelved or scrapped. Sometimes they are used for file servers or gaming. Adding older spec machines you already have is a great and cheap way to build a render farm and increase your total rendering power. But, bear in mind that newer generations of hardware are usually more power efficient, meaning that they will typically cost you less in electricity. 

 

You may want to consider how much electricity you will consume and whether that is worth the while with the combination of hardware and projects you wish to run on your render farm!

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If you'd like to dive deep into the details of render farms, then we've written an extended article about selecting CPUs for rendering.