Keeping a watch on energy

Section 3.3 of Part L2 of the Building Regulations states that ‘to enable owners or occupiers to measure their actual energy consumption, the building and engineering services should be provided with sufficient energy meters and submeters’.  The idea being that by monitoring power and lighting separately, operators can reduce energy usage by comparing actual consumption with targets, identifying unusual periodic changes and keeping annual records of seasonal consumption. 

As part of the Government’s drive to reduce carbon emissions and improve the energy performance of the UK’s building stock, it introduced the Building Regulations.  Part L2 of these underpins the need for new plants or commercial buildings, or those undergoing improvements, to look at their carbon emissions and utilise sub-metering.   In fact, the Government is currently reviewing the whole of Part L and is proposing a number of changes for 2010, part of which is the requirement for better accuracy of energy consumption by moving from an annual to a monthly calculation system. 

This will have an impact on the way building managers monitor their energy use and demonstrates just how important the Government sees sub-metering as a way to measure energy demand.  However, perhaps equally as important for businesses, is the fact that reducing energy consumption will lead to savings on fuel bills.  Given the difficult economic conditions, this is something that most organisations should be looking to do regardless of legislation, so by aiming to lower energy usage companies can effectively gain financially.

Making improvements

For a business to make improvements energy consumption needs to be analysed and this is the first step on the road to achieving greater energy efficiency.  The organisation can also consider whether it can actually account for 90% of its energy usage, which is another requirement of the Building Regulations.  Having an increased visibility of energy consumption will enable a company to reduce operational costs and manage utilities effectively.  Utilising monitoring equipment and software will identify where energy is being consumed and some of the technologies available are now recognised by the Government led Enhanced Capital Allowance Scheme.  This enables businesses to offset the cost of energy efficient products and technologies against their tax bill, providing they use equipment which is included on the Energy Technology List.


Sub-metering is a process that can allow energy consumption to be measured within particular areas of the site or building, or the electricity usage by a specific piece of equipment such as a computer.  Suitable for energy intensive organisations, sub-metering allows the company to identify exactly where energy saving opportunities exist, ensuring that measures are put into place where they will have the most impact.  For large-scale plants, this can offer a clear-cut solution to saving energy, without having to overhaul all processes and procedures.

The most basic way a company can assess patterns of energy use is to look at its electricity meter on a daily basis, which will show how much power has been used for that day’s activities.  However, existing regulations do not allow the user to rely on the electricity suppliers meter alone.  So another measurement system must be put in place, which will replicate the mains meter. 

Sub-metering can take place in two locations on an electrical circuit.  The first is to place a meter on the outgoing circuits from the main switch board or secondly on the circuits going into the sub-distribution board.  Both are just as effective as each other unless the lighting and power circuits are split. If this is the case, then it is necessary to use a split meter board to ensure accurate monitoring takes place.

Split meters are available in two types – Type A and Type B.  Type A boards are for single phase circuits and are designed for use in smaller commercial premises where loads are mostly lighting and heating.  Type B are for triple phase circuits and suitable for larger buildings over 1,000m².  Appropriate for existing and new build premises, the meters can be retrofitted to any existing distribution board to help users monitor their energy consumption.

Identify patterns

Using sub-metering to look at patterns of energy use can be an important stage in reducing consumption.  The process may highlight wasted energy during times of inactivity, for example weekends, lunchtimes and at night.  At the moment it is not commonplace for building managers to monitor each individual circuit, however the larger the group of circuits being measured, the less detail provided and so it’s harder to identify specific areas where consumption is high.  Instead, measuring at the lowest level will help to identify these problem areas so appropriate action can be taken.

As with all exercises to reduce energy usage, sub-metering will inevitably highlight processes or parts of the building that can be made more efficient with just a few simple changes.  Getting into good habits such as switching electrical equipment off when not in use, and not having lights on when there is sufficient daylight, will result in reduced energy consumption.  Although these may seem small steps, behavioural changes such as these can have a surprising impact on the amount of electricity that can be saved.

Reducing emissions

It can seem a daunting process to reduce carbon emissions and become energy efficient, but by sub-metering it becomes a much simpler process. Without measuring energy usage, it will never be fully understood and an informed decision cannot be made about how to manage it.  A wealth of products are now available in the market such as Schneider Electric’s range of PowerLogic Power meters and the EN40 meter, which helps organisations to identify the problem areas.  By identifying what is needed, the biggest step has already been taken and companies can ensure they are adhering to current and future legislation.

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