How to save money and energy on lighting systems

Understanding your current lighting costs

Unless your buildings have sub-metering of lighting or other circuits, it will not be immediately clear how much electricity you are using for lighting and its true cost impact. Even smart meters will not provide a detailed breakdown of how much electricity is used by different functions.

Two ways of assessing how much your lighting is costing your organisation and, therefore, how much effort you and your management team should put into this area, are the top-down and bottom-up approaches.

The top-down approach looks at total electricity use and then estimates the percentage that is used for lighting. Of course, this proportion will vary greatly depending on whether electricity is also used as the fuel for space and water heating.

For a gas-heated office without air-conditioning, lighting typically accounts for 50% of electricity use. The remainder will be accounted for by office equipment, kettles and other small appliances. In the bottom-up approach, the number of each type of lamp you use is determined.

This figure is then multiplied by the wattage of each type of lamp and the hours of operation. This will give the total lighting energy used in kilowatt hours (kWh). You can then work out how much your lighting costs by multiplying the energy used by the price you pay per kWh.

If you would like to use the bottom-up approach to assess how much your lighting is costing your organisation, a simple lighting costs calculator spreadsheet is available to download for free from our website.

Labelling light switches

Switches should be clearly labelled to enable staff to switch off lights in unoccupied areas. A lighting map will help staff understand the layout more easily.

Engaging staff

Engaging staff to simply switch off lights when they are not in use can save you energy for very little cost. We have developed a Staff Engagement Toolkit which has everything you need to get an improvement programme started.

Making the most of natural light

The need for artificial lighting can be reduced by making the most of available natural light. It’s worth bearing in mind that daylight is the best source of light available – in terms of colour and intensity. Here are four simple low-cost steps that can be taken to achieve this:

• Ensure that windows and skylights are clean.
• Remove furniture and other obstructions from near windows.
• Mount blinds and curtains above or to the side of windows so that they do not obstruct light when they are not in use.
• Locate as many desk-based workers near to windows as possible. The best orientation for desks is at right angles to windows. As light levels vary so much during the day in Scotland, savings will be maximised if lighting control is linked to available daylight. Automation will ensure that lights switch off when there is sufficient natural light.

Automate lighting control

In a building where many people use one area, automation is often the best way to prevent lights being left on unnecessarily. There are three main forms of automatic control – presence detection, daylight control and timers. It is worth bearing in mind that it is not always necessary to rewire lighting to take advantage of these automated forms of lighting control. Many switches and automatic controls can now operate wirelessly.

• Positioning of sensors – this is critical because lights need to come on just before someone enters a space, not after. This is also linked to lamp selection – lamps need to illuminate immediately and not take a while to attain full brightness.
• Manual override – this is necessary so that lights can be turned off or switched on if there is an obstruction between the sensor and the occupants.
• Toilet cubicles are private, and occupants aren’t ‘seen’ by sensors. Therefore, sufficiently long switch-on times – usually 7-10 minutes should be used in these areas. An alternative is to add more sensors to the same lighting circuit that work on heat, not movement. The most efficient approach is to have lights that are switched on manually but switch off automatically if no movement is detected – known as manual on, auto off.

Daylight control

In daylight control systems, photocells are used to detect when there is sufficient daylight and to switch off artificial light accordingly.

Some systems can dim lights and supplement natural lighting where necessary. For this technique to be successful, lighting subcircuits need to be separated so that photocells cover just the areas by windows where there is most natural light. Lights deeper in the building may need to be switched on permanently.

As with presence detection systems, manual override may be required. Sensors should be cleaned regularly, and this can be worked into your cleaning, lighting maintenance or facilities management contract should you have one.

Timers

Timers are particularly useful in retail applications where, for example, shop windows are illuminated during the evening when pedestrians continue to pass by. Foot traffic decreases during an evening so timers can be used to switch lights off at a certain time.

External lighting control

It is essential that exterior lights are not able to operate during daylight when they are not needed. Therefore, as a minimum, all exterior lights, whether installed for decorative or safety purposes, should be controlled by a daylight sensor.

Integral daylight and motion sensors are common on individual fittings but, if they are absent on yours, then a daylight sensor, timer or motion sensor should be fitted. It is worth noting that some timers need reprogramming when the seasons change. Others can be linked to a daylight sensor which automatically detects dawn and dusk, so the timer operates within these times.

In some cases, the most effective method of control may be to split the exterior circuits. In this way, a small number of lights operate permanently to show, for example, the layout of a car park, while the remainder switch on when a person is detected.

Office lamps

The lamp is the part of the lighting unit that emits the light.

Old incandescent lamps were often known as bulbs, though this term does not accurately describe many modern lamps such as LEDs.

Lamp technology has evolved rapidly in recent years. In particular, the advent of LED lamps for common applications is transforming the lighting market. For this reason, it is a good idea to keep lamp selection under regular review as technology may continue to improve.

Offices

Most businesses have offices or at least some administrative areas. Lighting in offices tends to be on for long periods, so this offers good opportunities for savings, particularly if the existing lamps are of an older, less efficient type. Planning lamp replacement in offices Before replacing lamps, it is necessary to establish whether existing light levels are adequate in the selected areas. If any areas are identified by staff as being poorly lit, this is a good opportunity to add more lighting or to increase the light output from existing fittings.

It is also important to ascertain whether there are any areas where lights need to be on permanently or where a specified level of illumination must be maintained. If in any doubt, contact your health and safety adviser, office manager or facilities manager.

Some areas may be over lit at present. For example, areas such as corridors require a lower level of illumination than the workspaces where detailed tasks are undertaken. Therefore, it may be that the number of lamps can be reduced or lamps with a lower light output (and running cost) can be used. Lastly, when considering replacing lamps, you need to be aware that different lamps produce different colour temperatures.

The only effective way to find out what colour of light suits the environment is to test out recommended lamps and to see what colour works best.

How to measure existing light levels

Light levels are easily measured with a simple and cheap lux meter.

Applications are also available for mobile phones and tablets. Any low lux levels should be improved as part of the lamp replacement process. In some areas, this may involve installing additional light units. Note that if you have daylight available unit available, this test should be carried out at night to ensure that the artificial light can always provide the necessary illumination when required.

Lamp replacement in offices

Many offices already have efficient lamps installed but checking for the following will reveal whether there are further opportunities to improve efficiency.

• Are there a significant number of halogen spotlights?
• Are large diameter T12 fluorescent tubes in use?
• Do the fluorescent lights ’blink’ when you switch them on?

If the answer is ‘yes’ to any of the above, then replacing lamps is likely to offer good savings.

Workshop lighting

Workshop lighting covers all kinds of industrial applications – from warehouses to machine processes. The level of illumination (lux) required will vary considerably according to the task being carried out.

It is worth remembering that good quality lighting control can reduce the time that lights are operating, so it pays to have adequate illumination in all places when needed.

Planning lamp replacement in workshops Before planning lamp replacement, ensure that you are making best use of existing available daylight. Windows and skylights should be regularly cleaned and a cleaning roster established.

In workshops there are two main types of lighting required, these are:

• general floodlighting
• it is essential to keep roof lights clean – especially in environments where the processes generate dust, airborne grease or other pollutants that can adhere to roof lights, diluting light quality.
• task lighting – to provide high levels of illumination in specific areas where (often detailed) tasks are being carried out.

External lighting

Firstly, check exactly what needs to be lit. It is very common for external areas to be lit at night unnecessarily (for example, where there is no security consideration, where there is no foot traffic or a staff car park without night shift). Any health and safety considerations should be checked carefully while carrying out this review.

The amount of light output and power consumed can be reduced by simply replacing the lamp with an equivalent lamp type but with a lower wattage. External lamp selection External halogen lamps are often rated as high as 500W.

In many cases, the lamp can be reduced in wattage without compromising performance or safety. Replacing a 500W lamp with a 150W lamp is a common way to achieve a saving. External halogen lighting is not the most efficient available and lamps can be replaced by CFLs or modern LEDs, which provide equivalent performance at greatly reduced energy consumption and with longer life.

As with high level interior lighting, exterior lights on buildings are often hard to access, so expected life is an important component of overall cost. Car park lighting has traditionally used sodium vapour or metal halide lamps.

As with interior lamps, the most efficient alternative is now LED. On average, LED lamps use 25% of the power of equivalent sodium lamps and give much better colour rendering. In external lighting situations, reliable colour rendering can be important for security camera imaging. However, it should be noted that the LED replacement lamp will often require replacement of the complete lamp unit, which increases the overall cost of the job and extends the payback period.

External lights are often in operation for long periods but, as with internal lighting, lamp technology has moved forward in recent years.

Making the case for lighting upgrades

This guide has outlined several opportunities to save energy and money on lighting that exist in most organisations in Scotland.

To help you start planning the projects you could implement in your organisation, we have developed a free spreadsheet tool to help you calculate potential savings.

Accessing finance

Accessing finance is often a major barrier to the successful implementation of lighting projects and, ultimately, the business benefits that these projects can deliver. This is particularly true for SMEs.

If you wish to improve the lighting in your organisation by implementing some of the lamp replacement and lighting control projects outlined in this guide, it is likely you will need to access finance.

Whether the finance is from internal or external sources, our guide ‘Developing a business case for your efficiency projects’ will help you. It will show you how to prepare a robust business case to support your proposed investment decision and how to present a strong case for investment to your senior management or external lenders. You can download the guide here.