Fine-tune: unloaded power, motor efficiency
A fixed-speed compressor running unloaded still uses about 25% of its full-load power. Leave motor efficiency empty to use the IE3 minimum for that motor size.
- Per running hour
- Per day
- Per month
- Per year
Enter the motor power, your electricity price and the running hours.
- Making air
- Running unloaded, no air
How it’s calculated
The nameplate power is what the motor gives at the shaft, so the electricity it takes is a little more. Loaded, a compressor runs close to its nameplate power.
Electricity cost: about $500 per HP per year
This rule of thumb is for a compressor that runs around 6,000 hours per year (2 full shifts per day).
For example, let's take a 45 HP / 33 kW air compressor. If we run it for 6,000 hours per year, at 10 cents per kWh, we pay: 33 × 6,000 × 0.10 = $19,800 in electricity cost per year! Close enough for a rule of thumb :)
Of course, this heavily depends on the compressor size, the cost of electricity, and of course the running hours.
As a rule of thumb: 2 psi of pressure drop costs 1% extra energy. In SI units: every 0.1 bar of pressure drop costs 0.7% extra energy.
More in Compressed Air Rules of Thumb.