Motor Efficiency: When to Retrofit vs Replace an Old Motor
An old motor still running fine isn't necessarily still efficient. Here's how to decide between adding controls and replacing the motor outright.
Why 'still running' isn't the same as 'still efficient'
A motor can run reliably for decades while its efficiency has degraded, and older motor designs were typically built to lower efficiency standards than what's commonly available today — meaning even a well-maintained old motor may be consuming meaningfully more electricity than a modern equivalent for the same output.
Retrofitting: adding a variable frequency drive
For a motor running at a fixed speed regardless of actual load — common in pumps and fans — adding a Variable Frequency Drive lets the motor's speed match actual demand instead of running at full speed and throttling output mechanically. This is often the highest-return single intervention available, and doesn't require replacing the motor itself.
When full replacement is the better call
For a motor nearing end of life, already showing signs of degrading performance, or one significantly undersized or oversized for its actual application, replacement with a modern high-efficiency motor is usually the better investment than retrofitting controls onto a motor that's fundamentally the wrong fit or close to failure anyway.
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