Pneumatic or electric? It’s not a new question. The merits of each have long been subject o discussion, but a fair amount of confusion
continues to exist about which makes more sense for
For example, are you considering replacing a compressor and 200 pneumatic cylinders with electric actuators
because you think you’ll save on compressor costs? Or,
perhaps you are thinking about building a new machine
with pneumatics because 30 electric actuators are far too
expensive. Make the wrong decision in either case and you
could waste tens of thousands of dollars a year.
Evaluating And Comparing Competing
The technologies underlying pneumatic and electric
actuators are so different that one cannot be a drop-in
replacement for the other. Considered separately, each
has inherent advantages and disadvantages that must be
considered in relation to performance, component costs,
system costs and productivity gains.
Pneumatic actuators deliver high force and speed at low
unit cost in a small footprint. In fact, pneumatic cylinders
provide more force and speed per unit size than any other
technology, except hydraulic.
Other important characteristics of pneumatic actuators:
force and speed are independent of each other and can be
easily adjusted. The typical pneumatic application employs
over-sized cylinders, because pneumatic cylinders are
inexpensive, making a step up to the next largest diameter
feasible and practical.
Pneumatics are most economical when the scale of
deployment matches the capacity of the compressor.
Small compressors are efficient and economical when
they are employed to power a small number of pneumatic
devices. Large compressors are efficient and economical
when powering a large number of pneumatic devices. It is
important to take this seemingly obvious point seriously.
Make the wrong calculation and you will be facing unused
compressor capacity, which can be very expensive.
Another important facet of pneumatics: pneumatic component costs are low, but maintenance and operating costs
can be high. When cylinders need to be replaced, when
air lines must be installed and maintained, and especially
when paying for electricity to run the compressor, expenditures add up. According to the Department of Energy,
about 25 percent of the cost of compressed air is due to
maintenance, equipment and installation, while more than
75 percent is due directly to the cost of electricity.
To determine or anticipate the operating cost per pneumatic device deployed in a facility, you must consider
compressor load. To reiterate — typically, compressor efficiency is lower when the compressor is partially loaded.
Furthermore, if during the work week the compressors are
left powered on at no load, a substantial amount of electricity is wasted. Waste is increased by inadequate maintenance (air leaks) and non-essential use of the compressor.
These problems are not unusual because of the popularity
of over-sized compressors and cylinders.
It can be a real eye-opener to look at the operating cost
per pneumatic device employed in a facility, especially
if you have not made cost calculations for quite a while
and if the scale of your operations has shrunk. If there are
500 pneumatic devices using a compressor, your cost per
device may average $100 per year. But, if there are only
50 devices using a compressor, your cost per device will
be ten times greater, or $1,000 per year.
Electric actuators, in contrast to pneumatics, provide
precise control and positioning. They help adapt machines
to flexible processes and have low operating costs. They
are most economical when deployed in a moderate scale
in processes in which their performance advantages can be
By Gil Guajardo
Costs And Capabilities
Of Pneumatic, Electric