Cost Of
      Compressor Ownership

Cost of compressor ownership varies. Here are details about the many costs associated with compressor ownership.

Buying trends would indicate that if you're looking for a general purpose industrial air compressor up to 20 HP folks select a reciprocating unit which, anecdotally, are lower cost units than rotary screw or rotary vane type compressors.

For more demanding industrial applications, and in a wide range of available horsepower, the rotary screw seems to be the next most popular type of industrial air compressor.

The rotary vane, while still prominent, appears to be selected for specialty applications more often than the first two.

First Cost

If we ignore the time you spend on looking, your first cost of compressor ownership is, of course, the purchase of your air compressor.

What you are using your air compressor for, and the discharge flow rate and pressure needed for your applications will determine what size and type of compressor is required.

Compressor Maintenance

After purchasing or leasing the compressor, next on the ownership cost list is the maintenance of your compressor.

After the warranty period, who is going to fix the compressor when it goes down? Your staff, the compressor supplier, or a third party maintenance group? What are their labor costs, and what hours are expected to be consumed in both regular maintenance and emergency repair.

Spare Compressor Parts

Included in the maintenance part of the equation is the cost of the spare parts for regular maintenance, and parts costs for emergency repair.

The major compressor manufacturers will be able to provide a forecast of annual maintenance costs, the sum of which might help you decide to purchase a more expensive yet more reliable compressor, which will then, one would hope, provide you with lower compressor maintenance cost over the life of the unit.

Operation Cost

Since the vast majority of industrial air compressors in plants run on electricity, the details below will help you determine the operating cost of the unit you are considering purchasing.

There are many formulae available to help determine your operating costs. We will offer a simplified version. If you seek greater detail, a couple of sources are noted below for you as well.

You Will Need To Know

• What are your electricity costs per kWh
• The hp of your compressor
• Compressor annual run time
• Efficiency of the motor
• Conversion factor: hp to kw = 0.746
• Load factor

Reference the electricity costs, if you do not pay the bills at your company, ask the accounts payable person to check on your last company hydro bill. Make sure that delivery costs, etc. are included in the kWh amount.

Annual run time is the number of hours per day, times number of days per week, times 52 weeks a year, resulting in a number of hours per year.

Motor efficiency information should be available from the compressor manufacturer. In the absence of that information, work on the basis of 90% efficiency or see if this information is noted on the compressor motor plate.

If your compressor runs all the time, and only compresses air part of the time, the time it is actually compressing air is the load factor. When it is running unloaded, the motor will use less energy.

If you are contemplating a compressor that only runs when it is compressing air, the load factor would be 1. If in doubt, use a load factor of 0.8. That should suffice for most applications.

Here's what the simple formula to calculate your compressor operating cost looks like.

Let's throw a few numbers at it, shall we? Here's a chart with the numbers for our theoretical application, from which you may be able to extrapolate to your compressor.

And last, here's the formula referred to earlier, now with our theoretical application numbers plugged into the formula.

And when you do the math, you'll see that this relatively small compressor, will cost $4,887.00 per year in energy operating costs!

We know you've a real interest in reducing operating costs so you'll want to know that more than10% of a compressors total output is wasted through folks using your air for other than it's desired use, or leaked from your system. Save some real money every year by curtailing air waste, and ridding your plant of air leaks.

Compressor Heat Source

It is possible to provide a significant amount of heat for your plant from your compressor.

Since you want the air going into your plant to be as to cool as possible, a heat exchanger / aftercooler might be a way to recapture the compressor heat for reuse.

'Nuff said on this topic by me. Compressor heat reclamation is best left to the experts, of which I sure am not. Here is one.

More Running Cost Info

Other sources for information about the cost of running a compressor are the IR/ARO site, and also, some excellent information can be found at the Kaeser Compressor web site.

Compressor costs will escalate along with your compressed air requirements. Cost info and compressor sizing data is here.