# Simple Yearly Compressor Running Cost Calculator

A very simple calculator to calculate the total running costs (in EUR or USD) for your air compressor. Please see below for more information.

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### Results per year:

This calculator is very basic and calculates the total running hours, kWh used and electricity cost per year.

It is intended for simple reciprocating (piston) air compressors.The running time you enter should be the total running time in a day the compressor is actually working. If it runs on-off throughout the day (as is probably) the case, you will need to make a best estimate.

This calculator doesn’t work work rotary screw air compressors. Since rotary screw compressor switch between loaded, unloaded and stopped, a more advanced calculator is needed. The main difference is that screw compressors still use about one-third of ‘loaded’ energy when running ‘unloaded’.

Tips and info

Here are some tips for entering your numbers and an explanation of the calculations:

Compressor motor rating

This is the motor shaft (output) power. You can find this on the nameplate of the motor. Usually, for a ‘6 hp’ air compressor for example, you will need to enter ‘6’ here and select ‘hp’.

Motor electrical efficiency

You can find this on the motor nameplate. This is basically the ratio between power output and power input.

If you divide the output power by the electrical efficiency, you will get the electrical input power.

The electrical input power is always higher then the shaft output power, since a little is lost in the motor (mainly to heat).

For example. A motor with 6 kW output and an efficiency of 0.8 will use 6/0.8 = 7.5 kW of electrical power.

Running hours

Enter the running hours per day and the number of days per week this compressor is in operation.

These are the actual working running hours of the compressor, not your shops opening hours. You will need to make a best estimate.

For example: if you know that your compressors runs about half of the time and is stopped the other half of the time (on-off-on-off every 10 minutes for example), and you work 8 hours per day, enter ‘4’ here.

Electricity cost

Enter your cost of electricity here. This varies widely per country, area and type of consumer that you are.

Find this value on your electricity bill. Make sure to select the right currency (Usd or Eur).

Calculations / output

The total running hours that this calculator gives you is simply hours per day * days per week * 52.

The total kW used is calculated as follows:

If you entered HP as compressor motor power, the value is converted to kW first. 1 HP = 0.7457 kW

The kW output of your compressor motor is divided by the electrical efficiency to give the electrical input power that your compressor uses.

If we multiply the total yearly running hours by the electrical power input of the compressor, we get the total energy used per year, in kWh (kilo-watt-hour).

kW vs kWh

What’s the difference between kW (kilo-watt) and kWh (kilo-watt-hour).

a kW is a measure of power, like horse power.

a kWh is a measure of energy. 1 kWh means you use 1 kW for 1 hour.

Another unit to measure energy is the joule. 1 kWh equals 3.6 megajoules.

Electricity costs

Now we have the kWh used by your compressor, we can simply multiply it by your energy cost (in Eur or Usd per kWh) to get the total cost of energy in a year.