# How can we find out what compressed air costs?

A simple approach is to find out how much energy (electricity) the compressor consumed during a given period and how much compressed air was delivered during the same period. The amount of compressed air delivered is measured by a flow meter. This approach shows how many kWh have been used to produce 1 Nm³/h air in the specific system. The operating cost of 1 Nm³/h air can then be calculated based on the cost of one kWh from the electricity provider. However, this scenario does not consider the investment or maintenance costs of the compressed air equipment.

Expense estimates in this handbook are based on a screw compressor that provides 6080 l/min, with an engine power of 37 kW, and cost per kWh of 0.112 EUR. The result in this case is 6080 l/min x 60 min/h = 364.8 m³/h. So, energy consumption to produce 364.8m³ is 37 kWh, which means 37 kWh/364.8 m³ = 0.101 kWh/m³. The cost:

0.101 kWh/m³ x 0.112 EUR = 0.0113 EUR/m³. Assuming that 70% of the total cost over ten years is the cost of electricity, the total cost would be 0.016 EUR per produced Nm³.

To go further and evaluate the various users of compressed air within the facility, air consumption has to be measured at different points in the system. This can be complicated because external devices (flow meters) have to be connected to obtain specific levels of exactly how much compressed air is consumed in each place.