In many facilities, low-efficiency motors installed years ago are still running. Although these motors appear to run trouble-free, they quietly continue to consume extra energy. Replacing an old motor with a high-efficiency new one is one of the fastest-returning investments in most businesses. In this article we examine in detail when it makes sense to replace an old motor, how the payback is calculated, and the savings to be gained.

To learn about efficiency classes and the differences between them, see the electric motor efficiency classes article; here the focus is entirely on replacing old motors and payback.

Why Do Old Motors Cost More?

replacing an old motor with a high-efficiency motor

Most old motors run at an efficiency well below today's standards. An IE1 or lower-efficiency motor installed years ago consumes noticeably more energy than a modern motor while doing the same job. This extra consumption quietly accumulates on the bill every month.

Moreover, old motors may often have been rewound several times; each rewinding lowers the motor's efficiency a little more. These motors, which still seem to run, actually cost the business much more than you think. This is why renewal is an often-overlooked savings opportunity.

The Real Cost of a Motor

To understand a motor's real cost, looking at the purchase price is misleading. In a continuously running motor, the vast majority of the lifetime cost — often more than 90 percent — comes from energy consumption. The purchase price and maintenance are a small part of this total.

This fact explains why the decision to replace an old motor is so important. Because replacement directly reduces energy consumption, the largest cost item. A few points of efficiency increase turns into savings much greater than the purchase price over the motor's lifetime.

How Is the Replacement Payback Calculated?

The payback calculation is simple. First, the cost of the new motor is determined. Then the annual energy savings the new motor will provide is calculated: this depends on the efficiency difference between the old and new motor, the motor's power, the annual running hours and the electricity unit price. Dividing the cost of the new motor by the annual savings gives the payback period.

If the payback period is much shorter than the motor's expected life, replacement is clearly profitable. In high-power motors that run a lot, this period is often measured in months. For the effect of efficiency-class selection on payback, see the efficiency class selection article.

The Importance of Running Hours

How quickly the replacement pays back depends largely on the motor's running hours. While replacement pays for itself very quickly in a motor running 20 hours a day, the same investment pays back over a much longer time in a motor running a few hours a week.

This is why the smartest approach is to start replacement with the most heavily running motors in a facility. The most heavily running and oldest motors are the candidates that provide the highest savings with a limited budget.

Electricity Price and Savings

The electricity unit price directly affects the return on replacement. The more expensive electricity is, the more valuable the savings provided by the new motor, and the shorter the payback period. Rising energy prices make replacing old motors more attractive every day.

When doing a payback calculation, it is wise to consider not only the current electricity price but also possible future increases. Expensive electricity makes the replacement investment profitable much faster.

Rewind or Replace?

When a motor fails, businesses usually face two options: rewinding the motor or replacing it with a new one. Although rewinding looks cheap, each rewinding lowers the motor's efficiency a little more. Especially in a heavily running motor, continuing to run at low efficiency costs much more in the long run than the rewinding cost.

For this reason, when an old, heavily running motor fails, replacing it with a high-efficiency motor instead of rewinding is usually more profitable. In a low-use motor, rewinding can be a reasonable option. The decision again depends on running hours and the efficiency difference.

Which Motor to Replace First?

Replacing all motors at once is not always possible. In this case, prioritization comes into play. The most heavily running, highest-power and lowest-efficiency motors are placed at the top of the list, because they are the candidates that pay back fastest from replacement.

When these motors are replaced, the savings provided can finance the next replacement. Thus, with a limited budget, it becomes possible to achieve the highest savings in the shortest time.

Starting with an Energy Audit

The most correct way to determine which motors should be replaced is an energy audit. This audit measures the real running hours, loads and consumption of the motors in the facility. With this data, how much savings each motor will provide from replacement can be calculated clearly.

A replacement plan made with measured data instead of guesswork gives far more profitable results. The energy audit is the basis for correctly prioritizing the replacement investment.

Which Class to Upgrade To?

When replacing an old motor, which efficiency class to switch to is also important. In a heavily running application, switching directly to IE4 or IE5 provides the highest savings; in moderate use, IE3 may be enough. The decision should be made according to running hours and electricity price.

For the advantages of IE4, see the IE4 electric motor article, and for ultra premium efficiency, the IE5 ultra premium motors article. In motors that run a lot, switching to a higher class is usually the most profitable option.

Extra Savings with a Frequency Drive

When replacing an old motor, you need to consider not only choosing an efficient motor but also the right operating method. In variable-load pump and fan applications, adding a frequency drive multiplies the savings. Because in these loads power is proportional to the cube of speed; lowering the speed a little reduces energy consumption much more.

For this reason, replacement is often an opportunity to improve not just the motor but the system as a whole. The combination of a new high-efficiency motor and a frequency drive provides the lowest energy consumption.

Environmental Benefit

Replacing old motors is not only an economic but also an environmental gain. Less energy consumption means less fossil fuel and lower carbon emissions. Replacing old motors in a facility directly contributes to the business's sustainability goals.

For businesses aiming to reduce their carbon footprint, motor replacement is a step that is profitable in terms of both cost and the environment. In this respect, replacement is an investment in the future.

Incentives and Financing

In many countries, there are incentive mechanisms that support the switch to an efficient motor. Supports such as grants, tax advantages or low-interest loans shorten the payback period of the replacement investment even further. Businesses researching these supports makes replacement much more attractive.

In addition, the savings from replacement can form the financing of the next investment. A well-planned replacement program turns into a self-financing, sustainable cycle.

Timing of Replacement

You do not always have to wait for an old motor to fail before replacing it. A heavily running, low-efficiency motor may deserve replacement even while still running, because of the extra energy it consumes. In this case, waiting until the motor fails means delaying the savings that come back.

The right timing is determined by the payback calculation. If the savings the new motor will provide cover the investment in a short time, replacing it is sensible even if the old motor is still running.

Other Benefits of Replacement

A new high-efficiency motor provides not only energy savings. It heats up less, runs more quietly, lasts longer and requires less maintenance. These additional benefits take the return on replacement beyond energy savings. A more reliable motor also reduces unexpected downtime and production losses.

In this respect, replacement is not just a cost-cutting step but also an improvement that increases operational reliability. You can review all high-efficiency options in the high efficiency motors section.

Making the Replacement Decision

The decision to replace an old motor is made with a simple payback calculation and correct prioritization. Starting with the most heavily running and lowest-efficiency motors provides the highest savings with a limited budget. When deciding, you should look at the total cost of ownership, not the purchase price.

To build the most suitable replacement plan for your application together, you can get support from the DRG Motor team. A correct replacement strategy both lowers the energy bill and increases the facility's efficiency for many years.

The Effect of Rewinding on Efficiency

One of the most important factors lowering the efficiency of old motors is past rewinding. If a motor is rewound every time it fails, the winding and core are damaged a little in each operation and efficiency drops a bit more. A motor rewound several times may be running at an efficiency well below the class on its plate.

For this reason, especially when it comes to a motor that has been rewound more than once and runs a lot, replacing is almost always more sensible. These motors, which appear to be running, are actually a large source of unnoticed energy loss.

Savings That Finance Themselves

The nice thing about the replacement investment is that it can often finance itself. When the most heavily running motors are replaced, the savings provided form the resource to finance the next replacement. Thus, the facility can run a gradual replacement program with a limited starting budget.

This approach allows reaching the most efficient motors by spreading savings over time, without needing to make a large investment at once. A well-planned program turns into a sustainable cycle that grows with its own savings.

Creating a Motor Inventory

Before starting replacement, it is very useful to create an inventory of the motors in the facility. When the location, power, efficiency class, age and daily running hours of each motor are recorded, it becomes clear which ones are a priority. This simple inventory takes replacement decisions out of guesswork and bases them on data.

The inventory also forms a basis for future maintenance and replacement planning. Knowing in advance which motors will be changed when prevents unexpected downtime and emergency purchases.

What to Watch Out for During Replacement

When replacing a motor, you need to match not only the efficiency class but also the right power, speed, mounting type and protection class with the new motor. Choosing a motor of the same frame size and connection type as the old one makes installation easier. Wrong sizing prevents the expected savings even in the most efficient motor.

In addition, alignment and the correctness of connections should be checked when commissioning the new motor. Correct installation allows the new motor to maintain its rated efficiency from the start and lays the foundation for long-lasting operation.

A Simple Savings Example

An example makes the benefit concrete. Consider a medium-power motor running 24 hours a day under constant load. The few-point efficiency difference between this old, low-efficiency motor and a new high-efficiency motor means thousands of kilowatt-hours of extra consumption over the year. When multiplied by the electricity price, this difference reaches a significant annual amount.

This annual saving, compared with the cost of the new motor, reveals the payback period. In motors that run a lot, this period is usually surprisingly short; this shows that delaying replacement actually means losing money.

What Happens to the Removed Old Motor?

The old motor taken out of service during replacement also has value. The copper windings, iron core and cast body inside it are suitable for recycling; the scrap value can cover part of the replacement cost. In some cases, the old motor can also be used as a backup in a less critical or low-use application.

However, running a very low-efficiency motor continuously elsewhere goes against the savings logic; it is more correct to send such motors for recycling. Consciously handling the old motor makes a small but real contribution to the total return of the replacement investment.

Frequently Asked Questions

Does it make sense to replace an old motor? Especially in heavily running, low-efficiency motors yes; the energy savings of the new motor usually pay back the investment in a short time.

How is the payback period calculated? The cost of the new motor is divided by the annual energy savings; the resulting time is the investment's payback period.

Is it better to rewind or replace a motor? In heavily running old motors, replacing is more profitable; each rewinding lowers efficiency. In a low-use motor, rewinding can be reasonable.

Which motor should be replaced first? The most heavily running, highest-power and lowest-efficiency motors; these pay back fastest.

Is a motor replaced while running? Yes; a heavily running low-efficiency motor may deserve replacement even if not failed, because of the extra energy it consumes.

Which class to switch to in replacement? IE4 or IE5 in heavily running applications; IE3 is usually enough in moderate use.

Is Replacement Worth It?

Old, low-efficiency motors quietly load extra cost onto the business even though they appear to run trouble-free. Replacing them with high-efficiency new ones is one of the fastest-returning energy investments in most facilities. In motors with high running hours and electricity prices, the payback can be measured in months. With correct prioritization, a simple payback calculation and the use of a frequency drive when needed, replacing an old motor both lowers the energy bill and adds long-term value to the business.