Water is one of the most precious resources on the planet, yet it is often overlooked in industrial and laboratory cooling applications. While tap water may seem like an inexpensive and convenient option for cooing, it carries hidden costs – both financial and environmental. Even if a business isn’t directly paying for its water usage, excessive consumption places unnecessary strain on local water supplied and infrastructure. As water conservation becomes an increasingly critical issue, industries must rethink how they use water, particularly in cooling processes.

A closed cooling system, such as a chiller or an airblast cooler, provides a more efficient, sustainable, and cost-effective alternative to once-through tap water cooling. These systems recycle heat transfer fluids in a closed loop, reducing water waste, lowering operating costs, and preventing long-term damage to equipment. But how much could a business actually save by making the switch?

By working through a structured calculation, businesses can determine not only the annual cost of tap water cooling but also the break-even point where investing in a closed system becomes the more economical choice. Below, we outline the key calculations involved and provide a detailed worked example to illustrate the real savings potential.

 Step 1: Calculating the Annual Water Cost for Tap Water Cooling

To determine the total cost of using tap water, the following factors need to be considered:

1. Operational time data you’ll need for this calculation:
Hour of operation per day (e.g., 8 hours)
Days of operation per week (e.g., 5 days)
Weeks of operation per year (e.g., 50 weeks)

2.  Total Run Time Per Year:
Hours per day x Days per week x Weeks per year = Total Annual Running Hours

3. Water Consumption Information:
Flow rate of tap water (litres per hour)
Total annual water usage = flow rate x total annual running hours

4. Water Cost Calculation:
Find out your cost of water per 1000 litres (including supply and sewerage charges)
Annual water cost = total annual water usage / 1000 x cost per 1000 litres

Step 2: Calculating the Operating Cost of a Closed Cooling System

A closed system, like a chiller or airblast cooler, has running costs primarily associated with electricity consumption. To calculate this:

1. Power consumption factors you’ll need to know:
Voltage of Supply (e.g., 400V)
Phase of supply (single-phase or three-phase)
Current drawn at peak load (in Amps)

2. How to Calculate Power Required per Hour:
Voltage of Supply x Current Drawn at Peak Load ÷ 1000

3. How to Calculate Annual Electricity Cost:
Find out your electricity cost per kW/hr
Annual Electricity Cost = Power per Hour x Total Annual Running Hours x Electricity Cost per kW/hr

4. Total Cost of Ownership
Purchase price of the chiller or airblast cooler
Annualised cost (e.g. spread over 5-10 years)

Step 3: Determining Payback Period

One of the most compelling reasons to switch to a closed system is its ability to pay for itself through reduced water consumption. To calculate the payback period:

1. Annual Savings:
Annual tap water cost – Annual electricity cost of the system

2. Payback Period Calculation:
Purchase price of the chiller ÷ Annual savings
This result gives the number of years or weeks required for the savings to cover the initial investment