Let's face it, energy isn't cheap and finding ways to reduce energy costs is critical to the bottom line.



In our last article, we showed you ways to improve the performance of your air system and maximize efficiency to save money.


Now, we'll show you where you can save money by auditing your compressed air operations. This article presents a step-by-step approach on how to conduct an audit, what to look for, and how to implement the necessary changes.



Why carry out an audit?

Research has shown1 that over 75% of compressed air costs come from the electricity used to power your compressor over its lifetime. Any time a compressor works longer or longer than necessary, it is wasting energy and not working efficiently. In today's economy, eliminating every pressure drop, leak, and outdated technology is critical to reducing bottom line costs, which can mean millions of dollars for large-scale production facilities.



The most important thing to remember is that all parts of your air compressor system work together. If one part isn't working efficiently, other parts work harder to make up for the slack, meaning you're wasting money on energy and shortening the life of individual parts and the entire system.



The best way to understand how much your air system is costing your business is to perform a thorough audit to determine how much energy and power your compressors consume on a daily basis, and discover where improvements can be made.



How much does compressed air cost?
Compressed air accounts for more than $5 billion per year in energy costs in the United States alone, and accounts for approximately 10% of all electricity consumption in North America. Compressed air is not cheap nor the most efficient source of energy, so it is essential to ensure that you are only using your compressor for the jobs necessary.



How to calculate compressed air costs
To calculate your compressed air cost, you will first need to determine how many kilowatt hours (kWh) your compressor is using. To do this:

1. Determine how many hours per day the compressor is used. Remember to record only the actual run time in hours, and to do this accurately, use a stopwatch to monitor and record the "on" cycles. Repeat this for a work week for best results
2. Determine how much power (or wattage) the compressor is using while it is running (this can be found on the compressor nameplate). If it is not listed, multiply Amps x Volts to determine the power rating.
3. Determine the total kilowatt hours used. To do this, multiply the power rating by the number of hours the compressor is used and divide that by 1,000.

3000 watts x 4 hours per day / 1000 = 12 kilowatt hours (kWh/day)

Next, you'll need to calculate the cost per kWh to run your compressor during the day (which is 4 hours in our example). To do this, multiply your kWh above with the rate charged by your utility company per kilowatt. If the company charges 14 cents per kWh, its calculation will look like this:

$0.14 x 12 kWh = $1.68/day (4 hours run time)


How to calculate the cost per year

Compressed air formula cost

Now it's time to multiply the above number to determine how much you spend on compressed air during a year. There are several ways to calculate this, however we have listed the simplest formula2 below.



*Pro Tip: Most of the numbers needed below can be found on the nameplate of your compressor. You will also need to perform this calculation twice; once for the cost of the compressor at full load and once for the cost of the compressor at part load.


Total cost/year = Motor HP x (0.746) x total operating hours (per year) x electric rate ($/kWh) x (% load time) x (% full load) / motor efficiency.

Ex. 1: Cost/year fully loaded = 250HP x (0.746) x 8000 x ($0.14 per kwh) x (.85) x (1) / motor efficiency (.95) = $186,892.63

Ex. 2: Part load cost/year = 250HP x (0.746) x 8000 x ($0.14 per kwh) x (.15) x (.25) / motor efficiency (.90) = $8,703.33

Combined Annual Energy Cost: ($186,892.63 + $8,703.33) = $195,595.96



Formula key:

HP: total rated power of the motor. This number may be higher than what is listed on the nameplate, so check the equipment specifications as well.)

Service factor: How far above the rated power the compressor can operate without damaging the motor. It can be found on the nameplate.

Total Running Hours: Total hours the compressor is running per year. Take the number you found to determine kWh per day, multiplied by the number of days per year that the compressor runs each year. Example: 4 hours a day, 6 days a week, 52 weeks a year (4 x 6 x 52) = 1248 hours a year.
Electric Rate: What the utility charges per kilowatt hour (kWh) of energy ($ per kWh).
Percent Loaded Time: Total amount of time the compressor is running.

Engine efficiency: rating given at the operational level; can be found on the nameplate.

This number is probably higher than you expected, but that's okay. It's never too late to audit your air system, implement changes, and reap the benefits of energy savings. However, we recommend that you start examining your compressor system today.

How to perform an audit

For the most accurate audit results, we recommend getting a professional diagnosis: a diagnostic technician will use data logging equipment to measure your load profile (the CFM and PSI you are using versus what you actually need to get the job done) .

From this data, you'll be able to see graphs that show exactly where you're wasting energy (and money). This data is critical in pinpointing any irregularities or air loss that is causing your air system to overwork and overcompensate.


An audit will consist of many measurements and factors3, and a complete assessment can be completed in as little as 8 hours or up to a few days, depending on the complexity and size of your system. It is recommended to check the items listed below to perform a thorough analysis of your compressor system.



1. Eliminate leaks and pressure drops
These are the culprits for the majority of wasted energy costs, so be sure to identify and repair any leaks found in your air system pipes. Even a 1/8-inch diameter hole in a 100 PSI system can add up to $1,200 in wasted energy over a year.4 Common places where leaks can be found are:

• Aging pipe – along air lines, especially corroded joints
• Couplings: check seals, they could be damaged by installation/use
• Drain Valves – Look at receivers, filters and all other equipment with valves
• Accessories: Accessories may have become loose over time.
• Flange connectors – close to where gaskets should be replaced
• Flexible hoses: may have cuts or cracks caused by abrasion.
• Collectors: close connections nearby
• Pneumatic Tool Ends – Check Connectors and Seals for Leaks

In addition to eliminating leaks, think about ways to reduce pressure drops throughout your air system, especially those with long runs of air pipes. One solution might be to reduce your pipe diameter from 3" to 2", effectively decreasing pressure drops by increasing PSI. Another solution could be to shorten the distance (travel) between your compressor and your air unit.



2. Check the air filters
Efficient Air Line Filter Clogged filters increase energy costs by reducing flow rates and removing fewer particles over time, forcing the compressor to work harder and pass harmful, poorly filtered air through the entire system. . If left unchecked, this can cause costly repairs in the future.



We offer high efficiency line filters to maximize savings at the air end. Regularly clean or replace all your filters and make sure you use the right ones first. Remember, dirty, unfiltered air will damage your compressor system, piping, and air tools.



3. Eliminate artificial demand
Manufacturers will use higher pressures (PSI) to overcompensate for pressure drops, leaks, and flow fluctuations to ensure flow demands (CFM) can be met. This creates artificial demand capacity that is often 25 percent or more higher than is actually needed. This can throw off your calculated costs and force your compressor to work harder than necessary and waste air in the process.



Operating at the lowest possible pressure will greatly reduce wasted energy, so instead of manually increasing pressure to meet demand, consider a flow controller or pressure regulator to help increase the efficiency of the air you already have. is producing.



4. Consider a pressure regulator
Pressure regulators strictly control air pressure and keep your air cap tools running efficiently with minimal wasted air. Some regulators even have built-in filtration included for maximum protection. Consider using them at your air terminal locations.



5. Evaluate heating and air dryer expenses
High Efficiency Air Dryer Air compression quickly creates heat and condensation. Air dryers defend the longevity of your pneumatic machines and tools by cooling and removing moisture from the air that would otherwise contaminate the air and damage your compressor's tank, lines, and other components over time. Use the wrong type of air dryer and you will waste a lot of money if you overwork the dryer to serve a purpose it was not built for.



A refrigerated air dryer will work perfectly with scroll compressors or a rotary screw or piston compressor designed with a built-in aftercooler. Otherwise, a regular refrigerated air dryer will run longer and twice as hard to cool high-temperature air, resulting in wasted energy, shorter dryer life, and wasted money. There are high temperature air dryers designed for this purpose and they work efficiently with those heavy workloads.



Most of the electrical energy generated by a compressor is converted into thermal energy, which is often wasted. Smart applications (like a heat recovery unit) in your system can allow you to harness that energy to offset compressor costs. Take space heating, for example. For large commercial buildings, it is possible to use the heat generated by your compressor to heat the building, or even to heat water for several