Should you upgrade your motors to save energy?
9 September 2024 
When considering the future for your motors, you need to consider many factors including efficiencies and payback times. Richard Gee, ABB’s sales manager for LV motors in the UK, explores some of the other aspects that need to be considered in when upgrading motors.
Motor efficiency has come a long way in a relatively short space of time. Efficiency classes for motors were only standardised internationally in 2008, and at that time the highest defined class was IE3. Since then we’ve seen the introduction of IE4 motors. In 2019, ABB’s SynRM (synchronous reluctance) machine became the first commercially available motor to achieve IE5. More recently, the company has also launched a range of motors meeting the anticipated IE6 efficiency level in magnet-free SynRM designs.
Motor manufacturers have a vested interest in selling more motors, and particularly in selling new, high-efficiency machines. The case for upgrading is relatively simple – a motor’s purchase price is around 1% of its Total Cost of Ownership (TCO), while maintenance is a further 2%. The remaining 97% is the cost of running – energy costs. The more efficient a motor is, the lower its energy costs through its lifetime.
A typical motor can run for decades, so even a small improvement in efficiency will pay for itself several times over during the course of the motor’s operating life. With energy costs spiralling in recent years, the equation becomes even more compelling, and payback times of a matter of weeks are not unheard of.
As well as cutting running costs, improving efficiency is clearly good for the environment too. Against the wider backdrop of the drive towards net-zero, and the urgent need to reduce carbon emissions, it’s undeniably impressive how manufacturers are continuing to push motor efficiencies to the very limit. Indeed, just a few years ago, IE5 was considered purely theoretical. Not only has IE5 been achieved, but manufacturers are now offering and developing even higher levels of efficiency.
Offsetting costs
On paper, it might seem that upgrading to the highest efficiency motor available is a win-win. The purchase cost can, in theory, be offset through the new motor’s lower lifetime energy costs, while newer synchronous reluctance motors also tend to be more reliable, longer lasting and quieter, as well as offering other benefits. However, in the real world, no one wants to be replacing their motors each time a new one comes on the market. It costs money, takes a lot of effort, and may also require downtime. If a motor has only been in place for a short period of time then, unless you’re jumping several efficiency classes, the potential savings from upgrading might not be that impressive.
Furthermore, replacing a motor has an inherent carbon cost. The old motor will need to be disposed of, while a new motor needs to be manufactured, transported to site and installed. The actual carbon impact of this can be difficult to calculate, although this is hopefully set to change in coming years with the increased adoption of Environmental Product Declarations (EPDs). These aim to provide greater transparency of the true carbon profile of a product over its whole life.
To gain EPD certification, product manufacturers must provide complete transparency over the origin and carbon impact of all of the materials and processes involved in the manufacture, use and disposal of the device, both at the component level and as a whole. For now, EPDs are not mandatory, however ABB’s SynRM motor is one of an growing number of products which already have third-party verified EPD certification, in accordance with ISO 14025.
The other important factor to bear in mind is that there are now more options available for older motors than ever before. Repairing or rewinding an old motor if it fails will cost a fraction of what it would to replace it, and can be far more economical from a TCO perspective. There’s also an additional option in the form of refurbishment, which also includes rewinding and improving other elements. In terms of cost, this typically occupies the middle ground between repairing and replacing, and will return a motor to its original condition – or better. However, even a refurbished IE2 motor is still an IE2 motor. Take advice from your service provider as they should be transparent and offer you the options to best suit your application needs.
If the motor is highly specialised then it may be difficult to find a suitable replacement, and it may also take some time to arrive. Motors that are critical to operations or are difficult to access might not be straightforward to replace, and a predetermined plan should be in place in the event of a failure. Motors with low operating hours may not be running for long enough periods to make a substantial difference to energy usage.
For older, less efficient motors, in particular, upgrading from, for instance, IE3 to IE5, can offer a vast improvement in efficiency and performance. IE5 motors have energy losses that are around 40% lower than IE3 motors, and the payback time for selecting an IE5 motor instead of an IE3 machine is often less than one year. Higher efficiency means increased profitability. In a typical application, an IE5 SynRM motor could save 16,730kWh per year, which equates to around 3,881kg of CO2.
Sweet spot
Each application is different, and the “sweet spot” where replacing becomes the more compelling option can vary according to the application. In addition, comparing datasheets at nominal power ratings won’t necessarily provide a true picture of how efficient a motor will be in situ. For instance, motor DOL (direct-on-line) efficiencies are typically reported on a pure sine wave, when realistically no UK industrial facility will have a power supply with a pure sine wave to start with. Reactive power levels can also increase line current and power losses in actual operation.
Unfortunately, there’s no rigid formula to tell you when to repair, replace or refurbish, because the answer is invariably: “it depends”. However, if you’re using a reputable, manufacturer-approved service provider then they will be able to provide an honest assessment of the options available. Lifecycle assessment services can also help to take a lot of the jeopardy out of a sudden failure, because in such an event you’ll already have a good idea of what the theoretical upgrade pathway is for a given asset.
Motor technology may be moving quickly, but even a 10-year-old motor can still have plenty of life left in it, particularly if it’s been maintained and serviced correctly. From a motor manufacturer’s point-of-view, it makes no sense to sell someone a motor that they don’t need, particularly when motor servicing has become so much more sophisticated and effective in recent years. There may not be a hard-and-fast equation as to whether upgrading, replacing or refurbishing is the best option, but talking to your manufacturer or service provider will ensure that you agree on the best possible option and have a suitable plan in place.
