Efficient Motors

15 July 2007

When a £500 motor can consume £50,000 in electricty in a 10 year operating life, saving a few pounds up front by buying a less efficient model could end up costing a lot more. Using energy efficient motors will keep overall energy consumption of buildings to a minimum. Ian Allan.

ENERGY EFFICIENCY IS ONE OF TODAY’S OVERRIDING CONCERNS and never seems to be out of the news. Yet, in the building services sector, users are missing a great opportunity to make their buildings more efficient. An electric motor in continuous duty consumes its own cost in energy during the first 30 days irrespective of its rating. After this time, the initial benefit of the low efficiency motor will have been expended and it will continue wasting money for the rest of its operational life.

The importance of energy efficiency to a motor’s life cycle costs is often not well understood. It is startling to realise that an 11kW motor costing about £500, can consume over £50,000 worth of electricity over a 10 year operating life. Among the hardest working of motors are those in building services, particularly HVAC. Yet, the energy efficiency of motors has not been high on the agenda in the building services sector.

One of the main reasons is the ‘somebody else’s problem’ syndrome - for anyone other than the end user, the issue of energy efficiency tends to be irrelevant, as it is only somebody else’s money that will be spent running the motors for the rest of their operational lives. When cost cuts need to be made, energy efficiency is seen as a ’nice to have’ that can be taken away without too much inconvenience.

The cost of more energy efficient motors is also often cited as a reason for specifying motors with a lower purchase cost. However, cheaper motors are not as cheap as they might seem.

High efficiency motors can give significant cost savings if used in the right applications. Compared to a standard motor, a high efficiency model can be up to 3 per cent more efficient. To make life easy for users, a labelling scheme has been introduced, where low efficiency motors were labelled EFF3; standard energy efficient motors, EFF2; and high efficiency motors, EFF1.

A 90kW high efficiency EFF1 motor could cost £1,200 more to buy than the standard EFF2 model, but will save £12,000 during a ten-year service life. The failure to fit a high efficiency motor may therefore cost the users £10,800 – a fairly hefty cost for what at the time may seem a small decision.

As well as saving energy costs, high efficiency motors also save on operating costs by bringing better reliability, reduced downtime and lower maintenance costs. Lower losses give the motor a better tolerance to thermal stresses, an improved ability to handle overload conditions, better resistance to abnormal operating conditions, and higher tolerance to inconsistent voltage and current wave shapes.

Energy efficiency is far more significant to the bottom line than the purchase price. Saving a few pounds up front by buying a less efficient motor could end up costing a lot more in the longer term. In terms of total life-cycle costs, the continued energy use of a motor is far more important than its initial purchase price.

Although even small differences in efficiency make big differences to a motor’s life cycle costs, the vast majority of the millions of motors in use in UK buildings today are not of the highest energy efficient type. This could all be about to change.

Air tight regulations
The new Building Regulations part L will have far-reaching implications for the way we live, work and build our houses in the coming years and is designed to deliver an improvement of around 25 per cent in the performance of new dwellings and an improvement of around 25-27 per cent in the performance of commercial buildings.

Instead of specifying particular values for the materials used in a building, the new regulations focus on the building’s overall performance. Under the new regulations, buildings will be checked to ensure that the calculated carbon dioxide emissions, as a result of energy consumption, are no greater than a specific target value for the type of building.

Energy efficient motors will be one of the simplest measures to introduce to keep overall energy consumption of the building to a minimum.

Best applications
What are the right applications for high efficiency motors? Used with an emergency pump that only runs a couple of times a year, a high efficiency motor will obviously not give a radical reduction of the running costs. But for applications in continuous use, a high efficiency motor is the better choice.

For new applications, buying high efficiency motors is usually the best option, as they can save many times their purchase cost over their average 15 year life span.

When choosing applications to suit high efficiency motors:
● Choose applications where motor running time is greater than idle time.
● Review applications that use high power motors, where the potential for cost savings can be significant.
● Select applications where loads are fairly constant, and where the motor operates at full load most of the time.
● Consider energy efficient motors for areas with high power costs.

Energy efficient motors are one of the technologies that qualify for Enhanced Capital Allowances (ECAs), which allow companies to deduct the full cost of the investment against corporation tax. The list of motors includes:
● all 2 and 4 pole motors between 1.1 - 90kW that meet the CEMEP EFF1 efficiency ratings
● all 2 and 4 pole motors between 90 - 400kW
● 6 and 8 pole motors between 5.5 - 315kW that meet the Water Industry Motor Efficiency Standards (WIMES) requirements for 6 pole motors.

Compared to the usual scheme of things, ECAs increase the value of the tax benefit and improve cash flow -the ECA is equivalent to a rebate of between 6 and 15 per cent.

Normally, the cost of capital goods is written off over a number of years - 25 per cent per year on the decreasing balance. Companies normally continue in this way for eight years, after which some 95 per cent of the value has been written off. In contrast, ECAs enable users to offset the full cost in the year of purchase, reducing the tax burden and improving cash flow. With £100,000 invested, with Enhanced Capital Allowances, and assuming 31 per cent company tax, you can claim £31,000 tax back.

For high use applications like HVAC and other building services uses, high efficiency motors are a must and, combined with refunded tax through the ECA scheme, they are a win-win deal for building managers.